Telephone

Invention and historical development of the telephone

Telephone set

Telephone network

Quality of telephone communication

Wireless telephone systems

Modern developments in telephony

Resources

The telephone (or simply, “phone”) is a telecommunications instrument that sends and receives sound such as voice messages and data across a certain distance. The term telephone is from the Greek roots tele, which means afar, and phone, which means voice or sound). In a broad sense, the telephone is a specific type of telecommunications that permits people to carry direct conversations over almost any distance.

The articulate speech is transmitted in a form of modulated electric current propagating along conductors or radio waves. The apparatus used for converting the verbal sounds into electromagnetic signals and vice versa is called a telephone set and is also commonly referred to as a telephone. Telephone communication is one of the most widespread and expeditious forms of communication. It has proved to be invaluable for an exchange of information in all areas of human life, whether it is business, government, science, public health, personal services, or social contacts. There were about 200,000 telephones in the world in 1887, approximately 30 million in 1928, 118 million in 1958, and more than 330 million in 1975. According to the University of California at Berkeley (School of Information Management and Systems), in 2004, it is estimated that over 1.3 billion main telephone lines exist in the world.

The general concept of the telephone as a system involves a number of elements. First, there is the telephone apparatus itself. Next, there is a variety of means for conveying the electromagnetic signals over distances (transmission paths). Third, the transmission paths are arranged in multi-leveled structures (networks) in a way that permits to interconnect (switch) any desired telephone sets upon request. And, finally, there are signaling facilities for directing the switching operations, alerting the person called, and clearing the circuits upon the completion of the call.

The scientific and technological discipline that studies and develops all of the telephone-system’s constituents is called telephony. Many problems in telephony draw on the principles and techniques of the electromagnetic theory, the theory of linear and nonlinear circuits, the probability theory, and the queuing theory.

Invention and historical development of the telephone

Electrical telecommunication originated in the nineteenth century, with the invention of the telegraph—a method of transferring intelligence between distant places through metallic wires in a form of spaced bursts of electricity. A sender, using a special letter code, produced regulated electrical pulses in a circuit. These signals were converted at the receiving end into a pattern of sound clicks, which was decoded by an operator or an automatic device. The next logical step beyond sending of non-articulate messages was the instantaneous transmission of conversation over wires. The intricate and very individual nature of sounds produced by the human vocal cords with the participation of the lips, as well as of the oral and nasal cavities, made this task difficult to accomplish. Articulate (spoken) speech involves not only the elementary sounds and their assembly into syllables, words, and sentences, but also infinite variations in accent, emphasis, intonation, and voice timbre— characteristics of no importance for other types of communication.

The inventor of the telephone is not entirely agreed upon. Among the inventors who have been awarded the honor include American Scottish-Canadian scientist and inventor Alexander Graham Bell (1847– 1922), American electrical engineer Elisha Gray (1835– 1901), Italian inventor Antonio Mencci (1808–1896), and German inventor Johann Philipp Reis (1834– 1874). In fact, they all spent time and effort researching and developing the telephone. The accomplishments of Bell will be discussed here.

By no chance, the invention of a way to transmit the human voice electrically was made by a man deeply involved in the study of vocal physiology and the mechanics of speech. A native of Scotland, Alexander Graham Bell inherited from his father, who was a famous professor of elocution and an author of several textbooks on speech correction, a profound interest in speech and hearing theory. He put his knowledge to work primarily for the teaching of the deaf. Being interested in electricity, Bell set up a little laboratory and experimented on transmission of sound tones over an electric circuit in an attempt to make a “harmonic telegraph”—a device capable of sending multiple telegraph messages simultaneously over the same wire. On the basis of his experimental observations, Bell gradually came to the conclusion that oscillations of air pressure (sound waves) could be used to modulate the intensity of electric current in a circuit. Using his knowledge of ear anatomy, Bell attached one end of a metallic organ reed to a thin diaphragm intended to simulate the eardrum. In presence of even weak air-pressure variations caused by the human voice, the diaphragm forced the metallic reed to oscillate in front of the electromagnet and, therefore, to undulate the electric current in the circuit.

Telephones successfully served the public for almost 23 years before scientists could explain theoretically why the telephone worked. Bell’s perception of an analog relationship between sound pressure and electromotive force was one of the most fascinating examples of the ingenious intuition in the history of technological discoveries.

Bell first started testing his device for voice transmission in June 1875, and patented it nine months later. The demonstration of the working apparatus at the Philadelphia Centennial Exposition attracted substantial public interest, which helped to raise some additional monetary funds. On August 1, 1877, with Bell’s four patents as a tangible basis for a wide manufacturing of a speaking telephone, the Bell Telephone Company was formed. Bell outlined a general concept of a telephone system as a universal means of voice communication between individuals, at any time, from any location, and without any special skill requirements. This concept might seem obvious today, but it was far in advance of any existing techniques of its time. Giant technological and organizational efforts were required to make Bell’s vision of a telephone communication a reality.

The number of existing telephones at that time were 778, but rapidly growing demand presented the challenge of operating the existing telephone while producing new ones. The first telephone subscribers were directly connected to each other. Under such arrangement, a community of 100 subscribers used 9,900 separate wire connections. For 1,000 subscribers the number of needed wire connections was more than 100 times bigger. The evident impracticality of full-time point-to-point connections stimulated the idea of a central office, or exchange. All the telephone sets in a particular area, instead of being wired permanently to each other, were connected to the same central office, which could establish a temporary link between any two of them on demand. Trained operators on a switchboard initially performed the process of line connecting and disconnecting (switching). However, with more and more telephones coming into use the manual switching was becoming increasingly complex. In 1891, the first automatic switching system was introduced.

As local telephone lines emerged and expanded, the idea of the creation and commercial operation of long distance telephone communication became a necessity. Unfortunately, the already existing telegraph lines were of little use for this purpose. Feeble electric currents used in telephony were rapidly dissipated (attenuated) on their way through iron wires. Compensating for attenuation was one of the main problems of telephony during its first 50 years. Considerable success in reducing the attenuation was achieved by using copper in place of iron wire. The innovation extended the limits of the voice transmission through bare wires to a distance between Boston, Massachusetts, and Chicago, Illinois—1,180 mi (1,900 km)—in 1893. Later, the effectiveness of wire lines was crucially increased by inserting inductances, or loading coils, at regular distances in a circuit. For crossing small bodies of water, telephone lines were laid in a form of insulated cables instead of bare wires. The invention of radio transmission at the beginning of the twentieth century led to the development of wireless telephone links and accelerated creation of the worldwide telephone system.

Long-haul facilities grew swiftly. In 1900, toll lines totaled 621,000 mi (1 million km) of wire. It took only 25 years to increase this number by a factor of ten. In 1925, almost one-half of the long-distance circuits were cable. The first transatlantic telephone cable (TAT-1) became operational in 1956. Nine years later, the first transatlantic telephone satellite Earlybird went into service.

Telephone set

A typical telephone instrument (see Figure 1) includes a number of main blocks (a switchhook, a ringer, a dial, a receiver, a transmitter, and a balancing network), which make it capable of numerous operations. 1) It requests the use of the telephone system when the hand-set is lifted, and signals the system that a call is finished when a caller returns the handset to the cradle. 2) It announces the incoming call by sending audible signals. 3) It sends to the system the telephone

number that is specified by the caller, who rotates a dial or presses number keys. 4) It converts the speech of the caller to electrical signals for transmission through the system and changes received electrical signals to speech. 5) It controls the level of unwanted sounds.

The switchhook interrupts the connection with the central office when the telephone set is idle (the handset is on the cradle) and completes the circuit whenever the handset is lifted off. The ringer is initiated by the system each time when an incoming call is waiting. Alternating current passing through a coil drives a permanent magnet, which makes the attached clapper periodically strike the bell.

The rotary dial is an electric contact that interrupts the circuit periodically sending to the central office a series of current pulses, corresponding to the identification number of the telephone called. When the tone dialing is used, as in touch-tone service, pressing of a number key results in sending a signal of two frequencies to the central office circuit, which identifies it and accordingly sets up the switching for the communication path. The use of tones speeds up the dialing operation and allows sending commands and control information directly to the called location.

The telephone transmitter responds to acoustic frequencies from 250 to 1,000 Hz. It consists of an electrical capacitor adjacent to a diaphragm, so that air-pressure vibrations caused by sound make the membrane produce changes in the value of capacitance of the circuit and, therefore, the variable electric voltage. As a result, a pulsating direct current occurs.

The typical receiver consists of a lightweight diaphragm attached to a permanent magnet associated with a coil of wire. When the alternating current of the telephone signal passes through the winding of the coil, changes are produced in the magnetic forces acting on a permanent magnet. The diaphragm moves in response to these variations, creating an acoustic pressure, more or less exactly reproducing the original sound wave from the distant telephone transmitter.

Sidetone is the sound of the speaker’s voice heard in his own receiver. To keep the level of this unwanted sound in acceptable range, the balancing network is used.

Special signals informing users on the status of their calls originate from the central office. When a caller lifts off the handset from the cradle the direct current flows through a complete circuit to the central office, which immediately registers the line initiating a call and places a dial tone on it. This tone signals to the subscriber that he may proceed with dialing the number of the called party. If the connection cannot be established, the tone generator in the central office produces one of three possible busy signals. A signal interrupted 60 times per minute means that the called party is busy. A signal interrupted only 30 times per minute indicates that the toll line between the central offices is busy, while a signal with 120 interruptions per minute means that all the intra-office paths are busy.

Telephone network

The telephone network’s structure may be defined as an entire plant of existing connections between telephone exchanges. It consists of three broad categories: local, exchange area, and long-haul networks.

The local network (see Figure 2) links telephones in residences and businesses to a central office serving a particular geographical area. The size of the area may vary from 11.5 sq mi (30 km²) in cities to 123.5 sq mi (320 km²) in the country. The telephone lines connecting a subscriber to the central office are called local lines or loops. Central offices are interconnected through the exchange area network, and all of the above are interconnected with toll (long-distance) exchanges. The telephone lines connecting one telephone exchange with another are called trunks in North America and junctions in Europe.

Each telephone is assigned a number indicating its location in the system. The switching network recognizes which telephone initiates the call and which telephone is to receive the call. From this information, it sets up the circuit connection for a signal path. Modern transmission facilities for conveying the electric analog of speech between telephone stations use diverse transmission paths, such as wire or cable circuits and microwave-radio or infrared-optical channels.

Quality of telephone communication

The intelligibility, naturalness, and audibility of transmitted speech are the main requirements for high quality telephone transmission. In technical terms, these requirements mean that: all the harmonic components of the human voice in the frequency range from 300 to 3,400 Hz pass through the communication channel; the loss of a signal during passing the channel does not exceed 30 dB; and the level of noise arising from all types of interference be at least 35 dB lower than the level of the main signals.

The quality of the telephone service is greatly dependent upon the structure of the networks by which subscribers are connected. The number of subscribers making telephone calls at one time is always substantially less than the total amount of subscribers. That is why the number of channels in the commercial telephone system is considerably less than the number of subscribers served by a central office (usually by a factor of seven to ten in a local office and 200–250 in toll exchanges). Because of such a design, a connection may be blocked when the telephone traffic is high. The quality of the automatic telephone service can be defined as the percentage of blocked (refused) calls during the hours of the heaviest telephone traffic. To reduce the incidence of channel overload, good planning based on statistical analysis is used.

Another way to improve network quality is to increase the amount of channels that can be carried by a single underlying medium. For example, in 1940, a coaxial cable could carry 600 voice channels. By the early 1950s, this amount increased to 1,860 voice channels and reached the number 13,200 in the 1980s. The microwave radio system experienced similar bandwidth growth, with 2,400 channels in the 1950s increased to 42,000 channels in the 1980s. Fiber optic technology, in 2005, provides even faster progress in this direction with hundreds of thousands of channels per single fiber (without even coming near its total capacity).

Wireless telephone systems

In wireless communication the information is superimposed on a carrier radio signal, which is sent through the air to a receiving location, where the original information is detected and isolated. Cordless, mobile, and cellular telephones perform all functions of the conventional telephone but partially use a radio link instead of wires.

The cordless telephone uses low-power radio transmissions only between the portable handset and its base. The telephone base is wired in a regular way to the telephone line completing the local loop to the central office. An internal antenna in the handset receives the transmission from the base unit over a range up to normally about 950 ft (300 m). The hand-set is powered by a battery, which is automatically recharged when placed in a receptacle in the base unit. When the user dials the number for the outgoing calls, the dial tones are transmitted to the base unit, which sends the tones to the regular telephone line. Cordless phones used the 1.7 MHz frequency range to communicate between the base and the handset when first introduced. However, since then, higher frequency ranges (49 MHz, 900 MHz, 2.4 GHz, and 5.8 GHz) have replaced it

The mobile telephone has no direct hardware connection with the conventional telephone line. It uses a high-power transmitter and an elevated antenna to establish a wireless link with the base station antenna serving a circular area of up to 31 mi (50 km) in radius. The base station receives and transmits on several different frequencies simultaneously, providing clear reliable communications. The control terminal of the base station directs telephone calls to and from the conventional telephone system, just like calls that are carried out entirely over wires. When the user in his moving vehicle lifts the handset of the mobile telephone to place a call, the control terminal automatically selects an available channel. If a channel is found, the user hears the normal dial tone and proceeds as usual.

The cellular telephone concept, first developed and implemented in the United States in the late 1970s, is a

method of providing high quality telephone service to subscribers when they move beyond the boundaries of the home area. This concept suggests dividing a service area into a number of small cells (see Figure 3). Each cell is served by a control terminal, which, like a local central office, can switch, transmit, and receive calls to/from any mobile telephone located in the cell. Each cell transmitter and receiver operates on a designated channel.

There are two essential features of the cellular concept: frequency reuse and cell splitting. Frequency reuse means that the same channel may be used for conversations in cells located far apart enough to keep interference low. This is possible, because each cell uses relatively low-power transmitter covering only limited area, so cells located sufficiently far from each other may use the same frequency. Cell splitting is based on the notion that cell sizes do not have to be fixed. A system with a relatively small number of subscribers uses large cells, which can be divided into smaller ones as demand grows.

The cells are interconnected and controlled by a central Mobile Telecommunications Switching Office (MTSO), which connects the system to the conventional telephone network and keeps track of all call information for billing purposes. During the call, the terminal at the serving cell site examines the signal strength once every few seconds. If the signal level becomes too low, the MTSO looks for a closest to the active user cell site to handle the call. The actual handoff from one cell to the next occurs without getting noticed by a user. Decision to hand off is made by the computer, based on the location analysis, the quality of the signal and potential interference.

The convenience and efficiency of wireless telephone communication is the reason for the impressive growth of this service. Recent market data indicate that there are, as of the beginning of 2006, just under 218 million cellular subscribers in the United States, compared with approximately 4.4 million in 1990, and 90,000 subscribers in 1984. Currently, cellular telephone service is available throughout the United States. The expansion of cellular networks on a global scale is based on employing low altitude low weight satellites. As of 2005, the total number of cell phone subscribers in the world is estimated at 2.14 billion, with about 80% of the world’s population in areas with access to cell phone coverage. The access coverage area is expected to increase to 90% by 2010.

Modern developments in telephony

Along with the television and the telegraph, the telephone is only a part of a large family of complex telecommunication systems. The past several years have seen the digitalization of the networks. Digital technology uses a simple binary code to represent any signal as a sequence of ones and zeros, somewhat similar to the Morse code, which assigns dot-dash combinations to the letters of the alphabet. The smallest unit of information for the digital transmission system is a bit, which is either 1 or 0. Binary codes are very stable against different distortions, and are therefore extremely effective for long-distance transmissions. Conversion to digital form allows for the integration of various modes of information management, opening new possibilities for information display, transmission, processing, and storage. As of 2005, over one-half of the information that passes through telephone lines in the United States ccurs through the use of computers and accessory equipment.

The introduction of the new transmission media (optic fibers) has extended the capabilities and quality of telecommunication services as a whole and telephone service in particular. The fiber optic cable has an almost infinite bandwidth, and is suited especially well for digital transmission. Current tendencies in optical fiber transmission technology include the development of new fiber materials producing a signal loss of no more than 0.001 dB per km as compared to 0.15 dB per km in existing silica-based fibers; the development of effective amplifiers; and the use of the fiber’s special transmission modes, called solitons, which are so stable that they preserve their shape even after having traveled thousands of miles.

For short distances a cable-free, easily deployed, and cost-effective communication for voice, data, and video is offered by an infrared (IR) optical communication system, employing air as the transmission medium. IR data transmission devices include personal digital assistants (PDAs), which use light-emitting diodes to emit infrared radiation. Infrared signal is another type of electromagnetic emission that is characterized by a considerably higher frequency than microwave. Due to higher frequency, an infrared signal is considerably more directional than a microwave one. The current commercial infrared systems were originally capable of providing reliable telephone links over a range of one half-mile and were ideal for local inter-building communications. However, in the 2000s, such systems are available throughout the United States with the use of wireless service providers.

Voice communications and data communications exist are integrated into a multimedia telecommunication network. Multimedia conferences or one-to-one multimedia calls are set up as easily as voice calls from a desktop device. The same device is used to access FAX and e-mail messaging. Multimedia enables people to combine any media they need to send, receive, or share information in the form of speech, music, messages, text, data, images, video, animation, or even varieties of virtual reality.

Voice over internet protocol (VoIP) telephones use a broadband Internet connection or other IP-based (Internet protocol-based) network in order to communicate. Such technology is also called IP telephony, broadband telephony, broadband phone, and other various names.

Conventional networks accommodate multimedia communication services, such as the direct participation of many conferees in an audio/video/data/image work session. Technology, economics, and even environmental factors stimulate people’s readiness to rely on networked contacts. Meeting somebody no longer implies being in the same place together. People separated geographically can still communicate face to face and collaborate productively. The emerging capabilities offered by the unified, intelligent telecommunication network gradually transform the way people interact, work, and learn.

As bandwidth improves in the early years of the twenty-first century (especially with the increased use of fiber optics and advanced wireless technologies), instruments that work as a telephone, plus functions as a computer, office organizer, camera, and television, are becoming commercially popular throughout the world.

KEY TERMS

Attenuation —Loss of energy in a signal as it passes through the transmission medium.

Bandwidth —The total range of frequencies that can be transmitted through a transmission path; the bigger bandwidth means bigger information carrying capacity of the path. As a rule, transmission path carries multiple channels.

Bel —Unit of measurement associated with a tenfold increase in sound energy. Decibel (dB) is one-tenth of a bel, and represents the smallest difference in sound intensity that the trained ear can normally perceive at a frequency of 1,000 Hz. In telephony, 0 dB level is prescribed to a reference point, which is usually the sending end of the transmission line.

Hertz —A unit of measurement for frequency, abbreviated Hz. One hertz is one cycle per second.

Optical fiber —Glass strands which act as light pipes for light beams created by lasers.

Switching —Process whereby the temporary point to point connection between telephone sets is established.

Transmission channel —The range of frequencies needed for a transmission of a particular type of signals (for example, voice channel has the frequency range of 4,000 Hz).

Resources

BOOKS

Bigelow, Stephen J. Understanding Telephone Electronics. Boston, MA: Newnes, 2001.

Gray, Charlotte. Reluctant Genius: Alexander Graham Bell and the Passion for Invention. New York: Arcade Publishing, 2006.

Elena V. Ryzhov

Telephone

The term telephone (from Greek tele, afar, and phone, sound) in a broad sense means a specific type of telecommunications which permits people to carry direct conversations over almost any distance. The articulate speech is transmitted in a form of either modulated electric current propagating along conductors or radio waves . The apparatus used for converting the verbal sounds into electromagnetic signals and vice versa is called a telephone set and is also commonly referred to as a telephone. Telephone communication is one of the most widespread and expeditious forms of communication. It has proved to be invaluable for an exchange of information in all areas of human life, whether it is business, government, science, public health, personal services, or social contacts. There were about 200,000 telephones in the world in 1887, approximately 30 million in 1928, 118 million in 1958, and more than 330 million in 1975.

The general concept of the telephone as a system involves a number of elements. First comes a telephone apparatus itself. Next, there is a variety of means for conveying the electromagnetic signals over distances (transmission paths). Third, the transmission paths are arranged in multi-leveled structures (networks) in a way that permits to interconnect (switch) any desired telephone sets upon request. And finally, there are signalling facilities for directing the switching operations, alerting the person called, and clearing the circuits upon the completion of the call.

A scientific and technological discipline which studies and develops all of the telephone-system's constituents is called telephony. Many problems in telephony draw on the principles and techniques of the electromagnetic theory, the theory of linear and nonlinear circuits, the probability theory , and the queuing theory.

Invention and historical development of the telephone

Electrical telecommunication originated in the nineteenth century, with the invention of the tele graph—a method of transferring intelligence between distant places through metallic wires in a form of spaced bursts of electricity . A sender, using a special letter code, produced regulated electrical pulses in a circuit. These signals were converted at the receiving end into a pattern of sound clicks, which was decoded by an operator or an automatic device. The next logical step beyond sending of non-articulate messages was the instantaneous transmission of conversation over wires. The intricate and very individual nature of sounds produced by the human vocal cords with the participation of the lips, as well as of the oral and nasal cavities, made this task difficult to accomplish. Articulate (spoken) speech involves not only the elementary sounds and their assembly into syllables, words, and sentences, but also infinite variations in accent, emphasis, intonation, and voice timbre—characteristics of no importance for other types communication.

By no chance, the invention of a way to transmit the human voice electrically was made by a man deeply involved in the study of vocal physiology and the mechanics of speech. A native of Scotland, Alexander Graham Bell (1847-1922) inherited from his father, who was a famous professor of elocution and an author of several textbooks on speech correction, a profound interest in speech and hearing theory, and put his knowledge primarily for the teaching of the deaf. Being interested in electricity, Bell set up a little laboratory and experimented on transmission of sound tones over an electric circuit in an attempt to make a "harmonic telegraph"—a device capable of sending multiple telegraph messages simultaneously over the same wire. On the basis of his experimental observations, Bell gradually came to the conclusion that oscillations of air pressure (sound waves ) could be used to modulate the intensity of electric current in a circuit. Using his knowledge of ear anatomy , Bell attached one end of a metallic organ reed to a thin diaphragm intended to simulate the eardrum. In presence of even weak air-pressure variations caused by the human voice, the diaphragm forced the metallic reed to oscillate in front of the electromagnet and, therefore, to undulate the electric current in the circuit.

Telephones successfully served to the public for almost 23 years before scientists could explain theoretically why the telephone worked. Bell's perception of an "analog" relationship between sound pressure and electromotive force was one of the most fascinating examples of the ingenious intuition in the history of technological discoveries.

Bell first started testing his device for voice transmission in June, 1875, and patented it nine months later. The demonstration of the working apparatus at the Philadelphia Centennial Exposition attracted substantial public interest, which helped to raise some additional monetary funds. On 1 August 1877, with Bell's four patents as a tangible basis for a wide manufacturing of a speaking telephone, the Bell Telephone Company was formed. Bell outlined a general concept of a telephone system as a universal means of voice communication between individuals, at any time, from any location, and without any special skill requirements. This concept might seem obvious today, but it was far in advance of any existing techniques of its time. Giant technological and organizational efforts were required to make Bell's vision of a telephone communication a reality.

The number of existing telephones at that time counted 778, but rapidly growing demand presented the challenge of operating the existing telephone while producing new ones. The first telephone subscribers were directly connected to each other. Under such arrangement, a community of 100 subscribers used 9,900 separate wire connections. For 1,000 subscribers the number of needed wire connections was more than 100 times bigger. The evident impracticality of full-time point-to-point connections stimulated the idea of a central office, or exchange. All the telephone sets in a particular area, instead of being wired permanently to each other, were connected to the same central office, which could establish a temporary link between any two of them on demand. The process of line connecting and disconnecting (switching) was initially performed by trained operators on a switchboard. However, with more and more telephones coming into use the manual switching was becoming increasingly complex. In 1891, the first automatic switching system was introduced.

As local telephone lines emerged and expanded, the idea of the creation and commercial operation of long-distance telephone communication became a necessity. Unfortunately, the already existing telegraph lines were of little use for this purpose. Feeble electric currents used in telephony were rapidly dissipated (attenuated) on their way through iron wires. Compensating for attenuation was one of the main problems of telephony during its first 50 years. Considerable success in reducing the attenuation was achieved by using copper in place of iron wire. The innovation extended the limits of the voice transmission through bare wires to a distance between Boston and Chicago—1180 mi (1,900 km)—in 1893. Later, the effectiveness of wire lines was crucially increased by inserting inductances, or "loading coils," at regular distances in a circuit. For crossing small bodies of water telephone lines were laid in a form of insulated cables instead of bare wires. The invention of radio transmission at the beginning of the twentieth century led to the development of wireless telephone links and accelerated creation of the worldwide telephone system.

Long-haul facilities grew swiftly. In 1900, toll lines totalled 621,000 mi (1 million km) of wire. It took only 25 years to increase this number by a factor of 10. In 1925, almost one-half of the long-distance circuits was cable. The first transatlantic telephone cable (TAT-1) became operational in 1956. Nine years later, the first transatlantic telephone satellite "Earlybird" went into service.

Telephone set

A typical telephone instrument (see Figure 1) includes a number of main blocks (a switchhook, a ringer, a dial, a receiver, a transmitter, and a balancing network), which make it capable of numerous operations. 1) It requests the use of the telephone system when the handset is lifted, and signals the system that a call is finished when a caller returns the handset to the cradle. 2) It announces the incoming call by sending audible signals. 3) It sends to the system the telephone number which is specified by the caller, who rotates a dial or presses number keys. 4) It converts the speech of the caller to electrical signals for transmission through the system and changes received electrical signals to speech. 5) It controls the level of unwanted sounds.

The switchhook interrupts the connection with the central office when the telephone set is idle (the handset is on the cradle) and completes the circuit whenever the handset is lifted off. The ringer is initiated by the system each time when an incoming call is waiting. Alternating current passing through a coil drives a permanent magnet, which makes the attached clapper periodically strike the bell.

The rotary dial is an electric contact that interrupts the circuit periodically sending to the central office a series of current pulses, corresponding to the identification number of the telephone called. When the tone dialing is used, as in touch-tone service, pressing of a number key results in sending a signal of two frequencies to the central office circuit, which identifies it and accordingly sets up the switching for the communication path. The use of tones speeds up the dialing operation and allows sending commands and control information directly to the called location.

The telephone transmitter responds to acoustic frequencies from 250 to 1,000 Hz. It consists of an electrical capacitor adjacent to a diaphragm, so that air-pressure vibrations caused by sound make the membrane produce changes in the value of capacitance of the circuit and, therefore, the variable electric voltage. As a result, a pulsating direct current occurs.

The typical receiver consists of a lightweight diaphragm attached to a permanent magnet associated with a coil of wire. When the alternating current of the telephone signal passes through the winding of the coil, changes are produced in the magnetic forces acting on a permanent magnet. The diaphragm moves in response to these variations, creating an acoustic pressure, more or less exactly reproducing the original sound wave from the distant telephone transmitter.

Sidetone is the sound of the speaker's voice heard in his own receiver. To keep the level of this unwanted sound in acceptable range, the balancing network is used.

Special signals informing users on the status of their calls originate from the central office. When a caller lifts off the handset from the cradle the direct current flows through a complete circuit to the central office, which immediately registers the line initiating a call and places a dial tone on it. This tone signals to the subscriber that he may proceed with dialing the number of the called party. If the connection cannot be established, the tone generator in the central office produces one of three possible busy signals. A signal interrupted 60 times per minute means that the called party is busy. A signal interrupted only 30 times per minute indicates that the toll line between the central offices is busy, while a signal with 120 interruptions per minute means that all the intra-office paths are busy.

Telephone network

The telephone network's structure may be defined as an entire plant of existing connections between telephone exchanges. It consists of three broad categories: local, exchange area, and long-haul networks.

The local network (see Figure 2) links telephones in residences and businesses to a central office serving a particular geographical area. The size of the area may vary from 11.5 sq mi (30 km2) in cities to 123.5 sq mi (320 km2) in the country. The telephone lines connecting a subscriber to the central office are called local lines or loops. Central offices are interconnected through the exchange area network, and all of the above are interconnected with toll (long-distance) exchanges. The telephone lines connecting one telephone exchange with another are called trunks in North America and junctions in Europe .

Each telephone is assigned a number indicating its location in the system. The switching network recognizes which telephone initiates the call and which telephone is to receive the call. From this information, it sets up the circuit connection for a signal path. Modern transmission facilities for conveying the electric analog of speech between telephone stations use diverse transmission paths, such as wire or cable circuits and microwave-radio or infrared-optical channels.

Quality of telephone communication

The intelligibility, naturalness, and audibility of transmitted speech are the main requirements for high quality telephone transmission. In technical terms, these requirements mean that: all the harmonic components of the human voice in the frequency range from 300 to 3,400 Hz pass through the communication channel; the loss of a signal during passing the channel does not exceed 30 dB; and the level of noise arising from all types of interference be at least 35 dB lower than the level of the main signals.

The quality of the telephone service is greatly dependent upon the structure of the networks by which subscribers are connected. The number of subscribers making telephone calls at one time is always substantially less than the total amount of subscribers. That is why the number of channels in the commercial telephone system is considerably less than the number of subscribers served by a central office (usually by a factor of 7-10 in a local office and 200-250 in toll exchanges). Because of such a design, a connection may be blocked when the telephone traffic is high. The quality of the automatic telephone service can be defined as the percentage of blocked (refused) calls during the hours of the heaviest telephone traffic. To reduce the incidence of channel overload, good planning based on statistical analysis is used.

Another way to improve network quality is to increase the amount of channels that can be carried by a single underlying medium. For example, in 1940, a coaxial cable could carry 600 voice channels. By the early 1950s, this amount increased to 1,860 voice channels and reached the number 13,200 in the 1980s. The microwave radio system experienced similar bandwidth growth, with 2,400 channels in the 1950s increased to 42,000 channels in the 1980s. The potential of the fiber optic technology promises even faster progress in this direction.

Wireless telephone systems

In wireless communication the information is superimposed on a carrier radio signal, which is sent through the air to a receiving location, where the original information is detected and isolated. Cordless, mobile, and cellular telephones perform all functions of the conventional telephone but partially use a radio link instead of wires.

The cordless telephone uses low-power radio transmissions only between the portable handset and its base. The telephone base is wired in a regular way to the telephone line completing the local loop to the central office. An internal antenna in the handset receives the transmission from the base unit over a range from 49 to 948.5 ft (15-300 m). The handset is powered by a battery which is automatically recharged when placed in a receptacle in the base unit. When the user dials the number for the outgoing calls, the dial tones are transmitted to the base unit which sends the tones to the regular telephone line.

The mobile telephone has no direct hardware connection with the conventional telephone line. It uses a high-power transmitter and an elevated antenna to establish a wireless link with the base station antenna serving a circular area of up to 31 mi (50 km) in radius. The base station receives and transmits on several different frequencies simultaneously, providing clear reliable communications. The control terminal of the base station directs telephone calls to and from the conventional telephone system, just like calls that are carried out entirely over wires. When the user in his moving vehicle lifts the handset of the mobile telephone to place a call, the control terminal automatically selects an available channel. If a channel is found, the user hears the normal dial tone and proceeds as usual.

The cellular telephone concept, first developed and implemented in the United States in the late 1970s, is a method of providing high quality telephone service to subscribers when they move beyond the boundaries of the home area. This concept suggests dividing a service area into a number of small cells (see Figure 3). Each cell is served by a control terminal, which, like a local central office, can switch, transmit, and receive calls to/from any mobile telephone located in the cell. Each cell transmitter and receiver operates on a designated channel.

There are two essential features of the cellular concept: frequency reuse and cell splitting. Frequency reuse means that the same channel may be used for conversations in cells located far apart enough to keep interference low. This is possible, because each cell uses relatively low-power transmitter covering only limited area, so cells located sufficiently far from each other may use the same frequency. Cell splitting is based on the notion that cell sizes do not have to be fixed. A system with a relatively small number of subscribers uses large cells, which can be divided into smaller ones as demand grows.

The cells are interconnected and controlled by a central Mobile Telecommunications Switching Office (MTSO), which connects the system to the conventional telephone network and keeps track of all call information for billing purposes. During the call, the terminal at the serving cell site examines the signal strength once every few seconds. If the signal level becomes too low, the MTSO looks for a closest to the active user cell site to handle the call. The actual "handoff" from one cell to the next occurs without getting noticed by a user. Decision to hand off is made by the computer, based on the location analysis, the quality of the signal and potential interference.

The convenience and efficiency of wireless telephone communication is the reason for the impressive growth of this service. Recent market data indicate that there are currently more than 100 million cellular subscribers in the United States, comparing with approximately 4.4 million in 1990, and 90,000 subscribers in 1984. Currently, cellular telephone service is available mainly in urban areas. The future expansion of cellular network on a global scale will be based on employing low altitude low weight satellites.

Modern developments in telephony

Along with the television and the telegraph, the telephone is only a part of a large family of complex telecommunication systems. The past few years have seen the digitalization of the networks. Digital technology uses a simple binary code to represent any signal as a sequence of ones and zeros, somewhat similar to the Morse code, which assigns dot-dash combinations to the letters of the alphabet. The smallest unit of information for the digital transmission system is a bit, which is either 1 or 0. Binary codes are very stable against different distortions, and are therefore extremely effective for long-distance transmissions. Conversion to digital form allows for the integration of various modes of information management, opening new possibilities for information display, transmission, processing, and storage.

The introduction of the new transmission media (optic fibers) has extended the capabilities and quality of telecommunication services as a whole and telephone service in particular. The fiber optic cable has an almost infinite bandwidth, and is suited especially well for digital transmission. Current tendencies in optical fiber transmission technology include the development of new fiber materials producing a signal loss of no more than 0.001 dB per km as compared to 0.15 dB per km in existing silica-based fibers; the development of effective amplifiers; and the use of the fiber's special transmission modes, called solitons, which are so stable that they preserve their shape even after having traveled thousands of miles.

For short distances a cable-free, easily deployed, and cost-effective communication for voice, data, and video is offered by an infrared optical communication system, employing air as the transmission medium. Infrared signal is another type of electromagnetic emission which is characterized by a considerably higher frequency than microwave. Due to higher frequency, an infrared signal is considerably more directional than a microwave one. The current commercial infrared systems are capable of providing reliable telephone links over a range of a half-mile and are ideal for local inter-building communications.

Both voice communications and data communications today exist separately. As technologies become more advanced, the best of both worlds will be integrated into a multimedia telecommunication network. Multimedia conferences or one-to-one multimedia calls will be set up as easily as voice calls from a desktop device. The same device will be used to access FAX and e-mail messaging. Multimedia will enable people to combine any media they need to send, receive, or share information in the form of speech, music, messages, text, data, images, video, animation, or even varieties of virtual reality .

Conventional networks can already accommodate some of the multimedia communication services, such as the direct participation of about 20 conferees in an audio/video/data/image work session. Technology, economics, and even environmental factors stimulate people's readiness to rely on networked contacts. Meeting somebody no longer implies being in the same place together. People separated geographically can still communicate face to face and collaborate productively. The emerging capabilities offered by the unified, intelligent telecommunication network gradually transform the way people interact, work, and learn.

Resources

books

Brooks J. Telephone: The First Hundred Years. Harper & Row, 1976.

Freeman, R.L. Telecommunication System Engineering. New York: Wiley, 1989.

periodicals

Chang, J.J.C., R.A. Miska, and R.A. Shober. "Wireless Systems and Technologies: An Overview." A&T; Technical Journal 72 (July-August 1993).

Udell, J. "Computer Telephony." Byte 19 (July 1994).

Elena V. Ryzhov

KEY TERMS

Attenuation

—Loss of energy in a signal as it passes through the transmission medium.

Bandwidth

—The total range of frequencies that can be transmitted through a transmission path; the bigger bandwidth means bigger information carrying capacity of the path. As a rule, transmission path carries multiple channels.

Bel

—Unit of measurement associated with a tenfold increase in sound energy. Decibel (dB) is one-tenth of a bel, and represents the smallest difference in sound intensity that the trained ear can normally perceive at a frequency of 1,000 Hz. In telephony, 0 dB level is prescribed to a reference point, which is usually the sending end of the transmission line.

Hertz

—A unit of measurement for frequency, abbreviated Hz. One hertz is one cycle per second.

Optical fiber

—Glass strands which act as "light pipes" for light beams created by lasers.

Switching

—Process whereby the temporary point to point connection between telephone sets is established.

Transmission channel

—The range of frequencies needed for a transmission of a particular type of signals (for example, voice channel has the frequency range of 4,000 Hz).

TELEPHONE

Telephone technology allows a person to talk to nearly anyone in any place who has similar equipment. There are substantial ethical questions related to the uses and abuses of the telephone. Among other things, the telephone is a communication system that provides political leaders, pollsters, and social science researchers with some understanding of public attitudes and behaviors. It gives voice to the needs and wishes of citizens as they attempt to make their views known to governments and corporations. Additionally, the telephone is a conduit for the delivery of professional services. As a result of these aspects of what has been an everyday but rapidly changing technology, considerable attention has been devoted to the telephone from ethical, legal, and policy viewpoints.

Historical Development

The term telephone is based on the combination of the Greek words, tele ("distant" or "afar") and phon ("sound" or "voice"); it was first used in France in the 1830s to name a crude acoustic device. By the mid-1800s something akin to a pair of tin cans connected by a taut string was known in the United States as the "lover's telephone." In 1876 Alexander Graham Bell (1847–1922) won a patent for a device that has come to be known as the telephone.

The traditional telephone operates by converting the mechanical energy of sounds carried in the air (the speaker's voice) into electrical impulses for transmission to a receiver. The receiver reverses the process, changing the electrical impulses back into vibrations. Those vibrations are heard as sounds. The original telephones transmitted electrical impulses by wires. Radio and other portions of the electromagnetic spectrum subsequently supplemented or supplanted wires as digital forms replaced analog.

The uses of the telephone have expanded to include multiple forms of data transmission, including fax, photo, and video image formats. Ancillary services have been created and have been widely adopted, including answering machines, caller-ID boxes, and telephone-based security systems. The Internet owes much of its success to the ability of users to go online by means of telephone lines.

In the early period of the telephone myriad uses were explored, including the "broadcasting" of news, opera, weather reports, and religious services. Some contemplated services never materialized: Bell speculated that the telephone might be used to communicate with the deceased. Other services did not materialize because they were outdated before they could deployed: France's national telephone company conducted extensive research in the 1960s to see if the telephone touch-tone pad could be adapted to serve as a home calculator. Yet other services were initially innovative and popular, but then, as technology continued to advance, they were left in the backwater. The fax machine and the French Minitel system are examples of this phenomenon.

Ethical Issues

PRIVACY, SECURITY, AND SURVEILLANCE. Among the early ethical questions was the way the telephone was used to invade privacy in the household and give outsiders access to household members. In particular the telephone allowed outsiders to make social connections with the members of a household, thus violating rigid gender and class roles. Ethical questions relating to various roles in the household, along with the power relationships among those roles, have been exacerbated by the telephone. For example, teenagers and parents come into conflict over appropriate norms for telephone use.

The telephone often leads to disruption of household routines and may allow for social subversion through practical jokes and harassing or obscene phone calls. Women especially have been victimized by such calls, though a surprisingly large number of men have been as well. Although commentators see great net benefits arising from the telephone, they also recognize the moral dilemmas that result from the "distant presence" (a phrase popularized by Kenneth J. Gergen) the telephone allows. The American humorist Mark Twain (1835–1910) was an early acerbic critic of the way the telephone could disrupt trains of thought and ordinary social interaction. In addition, characteristic of early telephone technology was the large proportion of homes that shared local service party lines; this meant that neighbors could listen in to conversations and learn family secrets.

Larger questions of privacy surrounded systematic wiretapping conducted by both licit and illicit organizations. Only a few years after the telephone was invented numerous devices were built to allow not only tapping but also recording of telephone conversations. (Many of these microphone devices also can be used to listen in on in-room conversations.) A wide variety of practices legal and illegal, moral and immoral, could be identified and documented.

Police forces and other governmental agencies sometimes carried out large-scale wiretapping not only in pursuit of wrongdoers but also to monitor those perceived as opposing government policy. In what has become a well-established cycle of innovation, new ways to communicate were followed by new ways to penetrate those forms, followed by steps to enhance privacy. Often a variety of codes would be devised to hinder attempts to collect data and conduct surveillance. The question of the areas in which people had a "reasonable expectation" of privacy was brought to a head when the U.S. Supreme Court decided in Katz v. United States (389 US 347 [1967], docket number 35) that public phone booths were not eligible for systematic tapping by the police.

Although monitoring of workers has been a perennial workplace issue, the telephone gave that issue added impetus because it greatly expanded the ability of managers to tap into the conversations of employees. Telephone companies often have conducted extensive monitoring, sometimes to the point of abuse, when they have used their own technology to monitor employees' behavior and comments. Switchboard operators once were notorious for eavesdropping, though sometimes that allowed them to interrupt the execution of crimes. (Eavesdropping, as opposed to service monitoring or surveillance by officials, is generally prohibited everywhere.) Many companies, including especially telephone companies, have published rulebooks and etiquette guides directed to their employees and managers regarding eavesdropping. While these efforts presumably reduced the problem, they have not been sufficient to extinguish the practice.

TELEMARKETING AND RESEARCH. Telemarketing is the offering of goods or services through sales presentations on the telephone. Because it can be a low-cost, high-profit enterprise, its rapid proliferation has become a source of general annoyance to the targeted public. The Direct Marketing Association and the American Marketing Association instruct their members not to use approaches that might be considered illegal. Moreover, there are numerous laws that regulate telemarketing at the national and local levels. Major moral dilemmas are related to this situation.

On the one hand, there are the claimed rights of businesses to "freedom of commercial speech," which includes the freedom to communicate with potential customers and participation in "fair and efficient markets." (These rights are protected strongly in the United States.) These rights often are carried out with increasingly powerful telephone support technology and database-mining software. On the other hand, individuals have a right to be left alone and not to have information about them collected in secret and without their permission. (These rights are protected strongly in the European Union nations and not as well protected in the United States.) Despite such efforts on both the technological front (such as caller-ID and call blocking) and the legal front (such as the compilation of "do not call lists" and the regulation of times when sales calls may be made), this problem persists.

Social science research and public opinion surveys often are reliant on polling by telephone. Numerous agencies and associations, such as the American Sociological Association (ASA) and American Association for Public Opinion Research (AAPOR) have created codes of conduct for their members, and in some cases governments have stepped in to create regulations in this area. Criminal penalties can be imposed for collecting data improperly by telephone. Many institutional review boards (IRBs) at universities require that researchers demonstrate that they will protect the data and not cause psychological distress, and this applies to telephone surveys as well as to medical experimentation. In more extreme cases, such as at the University of Newcastle in Australia, researchers are required to notify the target population in advance with a written information sheet that warns that telephone contact will be made and includes complete contact information.

UNIVERSAL SERVICE, SOCIAL EQUITY, AND DEMOCRACY. An important ethical component of national and regional policies for telephone technology is equitable distribution. As Claude Fischer (1992) has noted, in its early years the telephone could be considered only a luxury. However, what was an expensive enhancement to lifestyle has in contemporary society become a near necessity for most people.

For much of the twentieth century national telecommunication policies were aimed at subsidizing low-income and rural populations by indirectly taxing (through higher rates) urban and nonpoor telephone subscribers. This was done under the rubrics of social equity and economic development. In fact, in the United States the promise of universal service at an affordable cost was accepted by the government in exchange for the granting of near-monopoly status to the American Telephone and Telegraph Company (AT&T). However, the initial moral clarity of those policies has been obscured as advanced telecommunication technologies have proliferated, especially in the case of the mobile phone.

It is noteworthy that around the world hundreds of millions of subscribers have flocked to new mobile phone services. Those services allow subscribers to leapfrog the long waits and frequently high prices associated with wireline residential services. Moreover, cross-subsidization by ordinary telephone subscribers of low-cost services for schools and hospitals, as is the practice in the United States, means that many people with modest incomes are being penalized for the benefit of institutions in wealthy communities. (Mobile phone subscribers in the United States are exempt from these taxes.)

There can be little doubt that the telephone is an important adjunct to democracy on the level of political expression and as a bulwark against excessive governmental power. At the same time, terrorists and those seeking radical regime change can use the telephone to further their aims. In light of this situation many governments monitor telephone conversations and in some cases limit or prohibit mobile phone services. As instances, North Korea forbids civilian mobile phones on security grounds and Colombia's mobile phone networks were selectively turned off by the government in an effort to detect the location of cell phone-toting drug lord Pablo Escobar.

Public Use of Mobile Telephones

Each major advance in telephone technology has been accompanied by some social disruption. In most cases the disruptions have been transient. With the advent of the mobile telephone, however, high levels of conflict continue. These conflicts often may be understood in terms of what is known in psychology as the actor-observer paradox. The person who wishes to use the mobile phone (the actor) does so because he or she has good cause and with the expectation that others will understand and accept that necessity. However, the people around the user (the observers) view the situation differently. They feel that the mobile phone user is being selfish and self-indulgent and is failing to respect the conventions of polite society. The public use of mobile phones is likely to remain a source of normative conflict because the sources of irritation are not merely conventional but seem to go to the core of human cognitive processes. The result could be that as mobile phone users pursue the private pleasures of conversation there will be a reduction in civility and personal engagement in public places. Perhaps no better illustration of this process is the havoc wrought by drivers who are preoccupied by their mobile telephone conversations.

Provision of Professional Services

The ease and flexibility of telephone use have led many professional organizations to develop codes of conduct that allow their members to use the telephone, under appropriate conditions, to serve clients. This is the case with the many national and worldwide associations of lawyers, for instance. However, the potential for abuse also has led many organizations, such as the Legal Profession Advisory Council, to remind their members that whereas the telephone can be used to discuss and provide confidential information, both the professional and the client have to agree to this in advance. It further recommends that a scrambling device or other encryption technology be used. All advertisements for lawyers should bear the attorney's phone number prominently.

The question of recording telephone conversations is fraught with ethical and moral questions. In one instance (LEO 1738, 48/10 Va Lawyer Reg 23, April 13, 2000) the Virginia state bar association reexamined the subject of taping telephone conversations. That association concluded that all forms of wiretapping, along with one-party-consent recording of telephone conversations by lawyers, are prohibited. Although many people disagreed with that conclusion, it did arrive at the formulation that because wiretapping involves "deceit," the practice must be forbidden. This raises problems when, for instance, testers try to prove housing discrimination by pretending to be people other than who they are. The rules even make it unethical for an attorney who receives an obscene or threatening phone call to record it.

The American Medical Society counsels physicians that telephone advising and referral services should be used only to complement face-to-face interaction and that both the physicians and the clients should be well aware of the limitations of the medium. They urge that no physician make a clinical diagnosis or prescribe medications by telephone and at the same time be certain to elicit all-important information over the phone. They also should avoid generating large telephone bills that their patients or others have to pay.

Counseling by Telephone

Telecounseling has been defined as using the telephone for synchronous but distant interaction between counselors and clients for one-to-one conferencing. Obviously, such interactions are fraught with ethical issues. In response, the National Board for Certified Counselors (NBCC) says that its members should base the use of telecounseling on the needs and convenience of the client. The NBCC further stresses that telecounseling should only be a supplement to face-to-face counseling.

Confidentiality is an important consideration because it may be difficult to know precisely with whom one is speaking when one receives a telephone call. Thus, the American Psychological Association's guidelines warn counselors about privacy and confidentiality issues. The International Chiropractors Association of California has in its code of ethics the statement that its members "shall not discuss any patient information over the telephone with anyone without the patient's consent, preferably in writing." The International Association of Coaches instructs coaches to take precautions to ensure the confidentiality of telephone communications with clients.

In areas in which telephone counseling would be inappropriate professional codes of conduct underscore the importance of avoiding abuse. Thus, the Michigan Speech and Hearing Association urges that the telephone not be used for "diagnosis, treatment or re-evaluation of individual language, speech or hearing disorders." Medical and legal associations have guidelines that also are meant to avoid problems and underscore to their members that using the telephone may be construed as entering into a relationship with a client, with all the demands such a relationship entails.

More Complications Ahead

Because the telephone can obscure many of the ways in which people recognize each other or understand an evolving situation and can transcend distance, it opens new opportunities for ethically questionable or unethical behavior. In addition, as a result of the simplicity and power of the telephone, it has become a vital component of modern life. A variety of codes of conduct, laws, and corporate and governmental regulations have been developed to address these problems. However, these attempts have had incomplete success. Even as recent events are grappled with through norms and regulations, new telephone-based technologies that allow even more forms of use and abuse are complicating efforts to control telephone behaviors through technological countermeasures and moral and legal sanctions.

JAMES E. KATZ

SEE ALSO Communication Ethics;Communication Systems;Monitoring and Surveillance;Networks;Privacy;Security.

BIBLIOGRAPHY

Fischer, Claude. (1992). America Calling: A Social History of the Telephone to 1940. Berkeley: University of California Press. A profound analysis of technology's influence on social relationships and community. Fischer explores the integration of the telephone into society, thereby uncovering and illuminating important interplays between the communication processes and social structures.

Katz, James. (1999). Connections: Social and Cultural Studies of the Telephone in American Life. New Brunswick, NJ: Transaction. A detailed, empirical study of the ways telephone are used in ordinary (and extraordinary) circumstances. Explores norms and behaviors revolving around the telephone via methods including national surveys, interviews, and ethnographic observation.

Pool, Ithiel de Sola, ed. (1977). The Social Impact of the Telephone. Cambridge, MA: MIT Press. This path-breaking collection of historical and cultural studies on the telephone has become a classic and still has much to offer. It grew out of AT&T-sponsored lectures at MIT to celebrate the Centennial of the telephone's invention.

Ronnell, Avital (1989). The Telephone Book: Technology-Schizophrenia-Electric Speech. Lincoln: University of Nebraska Press. An eccentric but probing look at the deeper processes involved in the social and phenomenonological construction of the telephone. The volume is a wry postmodern achievement in both form and content.

Telephone

Sections within this essay:

A "telephone" is an apparatus for the transmission of human speech or other sounds over distances greater than the limits of ordinary human audibility. The business of transmitting information by telephone is quasi-public in character. The law treats telephone companies both as common carriers of information and as public utilities. As such, telephone companies are regulated by the Federal Communications Commission (FCC) at the federal level and by public utility commissions at the state level. Telephone systems may generally be owned and operated by a partnership, an individual, or a corporation.

Background

Invented by Alexander Graham Bell in 1876, the original telephone was described as a mere improvement upon the magnetic telegraph, which sent data as fast as electrons could move along wires. Unlike telegraph companies, however, telephone companies do not receive, transmit, or deliver messages in the ordinary sense of these terms. Instead, telephone companies furnish customers with networks, facilities, and devices through which conversations can take place over long distances.

The telephone-services sector began to develop in the late nineteenth century when several patents registered by Bell began to expire, while independent local telephone companies began to proliferate in major cities. At first, telephone service in the United States was predominantly local because satisfactory technology for transmitting long-distance calls did not exist. However, American telephony witnessed an explosion in technological innovations during the early twentieth century, including the invention of a "vacuum tube," which allowed phone conversations to be transmitted over distances of several miles.

The Bell telephone companies—under the parentage of the American Telephone and Telegraph Company (AT&T)—patented and deployed this technology across state lines. But they typically refused to allow independent telephone companies to interconnect with their long-distance service. As a result of this handicap and the intense price competition with the Bell companies, many independent telephone service providers chose to sell their companies to AT&T. By the advent of the 1930s, AT&T controlled approximately 80% of local exchange lines in the United States. These practices placed AT&T in the cross hairs of antitrust authorities, who convinced Congress of the need for regulation in this area.

Federal Regulation of Telephone Companies and Telephone Services

The Communications Act of 1934

After conducting a series of hearings on AT&T's growing dominance over American telephoning, Congress determined that AT&T and its competitors were public service corporations whose facilities and instruments were devoted to public use, which made them subject to two kinds of legislative control, state and federal. States may regulate the transmission of telephone communications wholly within state boundaries, Congress said, so long as such intrastate communications do not substantially affect interstate commerce. Once a telephone communication crosses state boundaries or substantially affects commerce in more than one state, Congress observed, the Commerce Clause of the U.S. Constitution gives only federal authorities the power to regulate such interstate communications. U.S.C.A.Const.Art. I, section 8, clause 3. Congress formalized these findings in the Communications Act of 1934.

The Communications Act of 1934 establishes a dual system of state and federal regulation for telecommunications services. 47 USCA sections 151 et seq. The act grants the FCC broad authority, but also clearly delineates a strict separation between interstate and intrastate jurisdiction, and denies the FCC authority over most intrastate communications. The act also establishes the Federal-State Communications Joint Board to hear disputes that involve questions concerning both interstate and intrastate telephone transmissions, and any other telecommunications dispute deemed to involve a mixture of state and federal concerns.

In determining whether the FCC has jurisdiction to regulate a particular telephone service provider, the focus is on the nature of the service at issue, since the FCC may regulate telephone services only to the extent of their interstate use. However, purely intrastate telephone facilities and services that are used to complete even a single interstate call can fall under FCC jurisdiction depending on the nature of that phone call. Thus, the FCC has authority to regulate use of an intrastate call made on a Wide Area Telecommunications Service (WATS) when that service is used as part of an interstate communications network. National Association of Regulatory Utility Commissioners v. F.C.C., 746 F.2d 1492 (D.C. Cir. 1984). Similarly, where a telephone company has all of its facilities within one state and solely engages in intrastate telephone communication except for its physical connection with carriers doing business in other states, it is still subject to federal regulation under the Communications Act as a connecting carrier. At the same time, the FCC does not have authority to order connecting carriers to continue interconnection agreements with interstate telecommunication service providers. Accordingly, connecting carriers are free to remove their interconnection with any interstate carrier, and thereby remove themselves completely from jurisdiction of the FCC.

Recent Amendments to the Communications Act of 1934

Telephone companies that are subject to federal jurisdiction under the Communications Act are also subject to any other applicable laws, regulations, or rules enacted by Congress or promulgated by a federal agency. On three occasions during the 1990s Congress amended the Communications Act of 1934, updating its provisions in light of technological developments and market conditions. In 1991 Congress passed the Telephone Consumer Protection Act (TCPA) to give Americans greater freedom at home from unsolicited commercial advertisements. 47 U.S.C.A. section 227. The TCPA generally imposes restrictions on unsolicited advertisements made through automatic telephone dialing systems, artificial or prerecorded voice messages, and telephone facsimile machines.

The FCC began fleshing out these restrictions when it promulgated a regulation requiring telemarketers to create do-not-call lists for consumers who ask not to receive further solicitation. The FCC also limited the hours during which telemarketers may call a consumer's residence (not prior to 8 a.m. or after 9 p.m.). Additionally, the FCC issued a rule flatly prohibiting the transmission of unsolicited advertisements via telephone facsimile machines. Finally, the FCC published a regulation requiring all artificial or prerecorded messages delivered by an auto-dialer to clearly identify the caller at the beginning of the message.

In 1992 Congress again amended the Communications Act of 1934, when it passed the Telephone Disclosure and Dispute Resolution Act (TDDRA). 15 U.S.C.A. section 5701. The TDDRA regulates how telephone carriers may offer pay-per-call services (e.g., 900 numbers), and prohibits unfair and deceptive practices undertaken by telephone carriers in connection with pay-per-call services, including mis-leading and fraudulent billing and collection practices.

Specifically, the TDDRA provides that any interstate telephone service, other than a telephone company directory assistance service, that charges consumers for information or entertainment must be provided through a 900 number unless it is offered under what is termed a "pre-subscription or comparable arrangement." That pre-subscription or comparable arrangement may be a preexisting contract by which the caller has "subscribed" to the information or entertainment service. The arrangement may also be made through the caller's authorization to bill an information or entertainment service call to a prepaid account or to a credit, debit, charge, or calling card. Telephone companies may not disconnect local or long-distance telephone service for failure to pay 900 number charges, and must offer consumers the option of blocking access to 900 number services if technically feasible. Telephone companies that bill consumers for pay-per-call and pre-subscribed information or entertainment services must show those charges in a portion of the bill that is separate from local and long-distance charges.

Despite increased regulation at the federal level, the telephone service market in the United States remained largely monopolistic for most of the twentieth century, continuing to be dominated by a few small companies in each region of the country. Congress attempted to increase competition by passing the Telecommunications Act 1996 (the "1996 Act"), which allows multiple "local exchange carriers" (LECs) to compete for customers. 1996 Pub.L. No. 104-104. The 1996 Act amends the 1934 Act by distinguishing between incumbent LECs (ILECs) and competing LECs (CLECs). ILECs are existing telephone service providers that have established a telecommunications network in a given market. CLECs are telephone service providers that seek access to an ILEC's market.

One way in which the 1996 Act attempts to improve competition is through "interconnection agreements" and "reciprocal compensation agreements." 47 U.S.C.A. section 251. "Interconnection agreements" require ILECs to make their telecommunications networks available (via purchase or lease ) to CLECs so that a phone call initiated by the customer of an ILEC may be connected to the customer of a CLEC, and vice versa. "Reciprocal compensation agreements" require the carrier for the customer who initiates a phone call to share some of its revenues from that call with the carrier of the customer who receives the call (the telecommunications industry describes the LEC of the customer who receives the call as the one that "terminates" the call and not the one that "receives" it). These requirements were challenged and upheld in federal court on two separate appeals, and are now under consideration by the U.S. Supreme Court. Illinois Bell Telephone Co. v. Worldcom Technologies, Inc., 179 F.3d 566 (7th Cir. 1999); Bell Atlantic Maryland, Inc. v. MCI WorldCom, Inc., 240 F.3d 279 (4th Cir. 2001). In a related case, the U.S. Supreme Court upheld FCC rules that require ILECs to lease their networks to competitors at heavily discounted rates. Verizon Communications, Inc. v. F.C.C., ―U.S.―, ― S.Ct. ―, ― L.Ed.2d ―, 2002 WL 970643 (U.S., May 13, 2002).

State Regulation of Telephone Companies and Services

State law regulates intrastate telephone services that do not substantially affect interstate commerce. It is the policy of each state to protect the public interest in having adequate and efficient telecommunications services available to every state resident at a just, fair, and reasonable rate. To carry out this policy and to regulate rates, operations, and services, state public utility commissions (PUCs) have the general power to regulate and supervise the business of each public utility within its jurisdiction and to do anything that is necessary and convenient in the exercise of its power. For example, state PUCs are typically given exclusive jurisdiction to determine whether a telephone utility should be permitted to close a business office in a given community.

PUCs are also commonly charged with the exclusive responsibility to enhance competition by adjusting regulation to match the degree of competition in the marketplace so that costs associated with running a utility do not deter new telephone service providers from entering the market. State PUCs must ensure that telephone rates are not unreasonably preferential, prejudicial, predatory, or discriminatory and are applied equitably and consistently throughout its jurisdiction. Additionally, PUCs may supplement federal law by enacting their own rules and regulations governing pay-per-call services, unsolicited advertisements, automatic dial announcing devices, or any other feature of local telephone service that might adversely affect consumers.

An individual, partnership, or corporation may not normally offer local telephone service without complying with PUC rules and regulations. In most states, the PUC requires that before a telephone company may provide local service each company must obtain (1) a certificate of convenience and necessity; (2) a certificate of operating authority; or (3) a service provider certificate of operating authority. PUCs may revoke or amend a certificate of convenience and necessity, a certificate of operating authority, or a service provider certificate of operating authority after notice and hearing if it finds that the certificate holder has never provided or is no longer providing service in all or any part of the certificated area. PUCs may also require one or more public utilities to provide service in an area affected by the revocation or amendment of a certificate held by a public utility.

Organized for public purposes to more efficiently serve its customers, telephone companies are usually granted special privileges and powers in addition to those that they possess as private corporations. For example, telephone corporations, telephone cooperatives, and foreign telephone companies are often given the power of eminent domain, which gives these entities a right-of-way to erect, construct, and maintain necessary stations, plants, equipment, or lines upon, through, or over private land. The delegation of the state's power of eminent domain has been held valid because of the public good derived from installing telecommunications systems on private property.

On the other hand, local telephone companies have no absolute right to use city streets to erect telephone poles or configure their facilities and networks. Instead, telephone companies must first obtain consent from the municipal authorities of the city in which they are seeking to provide telephone service. This consent is commonly manifested by the grant of a franchise from the governing municipal authority, and PUCs should not unreasonably restrict the rights and powers of municipalities in granting or refusing a telephone company the right to use city streets. However, cities, towns, and villages have no right to deny telephone companies all use of their streets, and when a municipal corporation unlawfully rejects a telephone company's application to erect poles and string wires along certain public streets, it abandons the right to prescribe the streets on which the line will be constructed.

AdditionalResources

West's Encyclopedia of American Law St. Paul: West Group, 1998

American Jurisprudence St. Paul: West Group, 1998

Organizations

Federal Communications Commission

445 12th Street S.W.
Washington, DC 20554 USA
Phone: (888) 225-5322
Fax: (202) 835-5322
E-Mail: [email protected]
URL: http://www.fcc.gov
Primary Contact: Michael K. Powell, Chairman

Public Utility Commission of Texas

1701 N. Congress Avenue
Austin, TX 78711-3326 USA
Phone: (512) 936-7000
E-Mail: [email protected]
URL: http://www.puc.state.tx.us/about/index.cfm
Primary Contact: Lane Lanford, Executive Director

Telephone

History

Throughout history, people have devised methods for communicating over long distances. The earliest methods involved crude systems such as drum beating or smoke signaling. These systems evolved into optical telegraphy, and by the early 1800s, electric telegraphy. The first simple telephones, which were comprised of a long string and two cans, were known in the early eighteenth century.

A working electrical voice-transmission system was first demonstrated by Johann Philipp Reis in 1863. His machine consisted of a vibrating membrane that opened or closed an electric circuit. While Reis only used his machine to demonstrate the nature of sound, other inventors tried to find more practical applications of this technology. They were found by Alexander Graham Bell in 1876 when he was awarded a patent for the first operational telephone. This invention proved to revolutionize the way people communicate throughout the world.

Bell's interest in telephony was primarily derived from his background in vocal physiology and his speech instruction to the deaf. His breakthrough experiment occurred on June 2, 1875. He and his assistant, Thomas Watson, were working on a harmonic telegraph. When a reed stuck on Watson's transmitter an intermittent current was converted to a continuous current. Bell was able to hear the sound on his receiver confirming his belief that sound could be transmitted and reconverted through an electric wire by using a continuous electric current.

The original telephone design that Bell patented was much different than the phone we know today. In a real sense, it was just a modified version of a telegraph. The primary difference was that it could transmit true sound. Bell continued to improve upon his design. After two years, he created a magnetic telephone which was the precursor to modern phones. This design consisted of a transmitter, receiver, and a magnet. The transmitter and receiver each contained a diaphragm, which is a metal disk. During a phone call, the vibrations of the caller's voice caused the diaphragm in the transmitter to move. This motion was transferred along the phone line to the receiver. The receiving diaphragm began vibrating thereby producing sound and completing the call.

While the magnetic phone was an important breakthrough, it had significant drawbacks. For example, callers had to shout to overcome noise and voice distortions. Additionally, there was a time lapse in the transmission which resulted in nearly incoherent conversations. These problems were eventually solved as the telephone underwent numerous design changes. The first phones made available to consumers used a single microphone. This required the user to speak into it and then put it to the ear to listen. Thomas Edison introduced a model that had a moveable listening earpiece and stationary speaking tube. When placing a call, the receiver was lifted and the user was connected directly to an operator who would then switch wires manually to transmit. In 1878, the first manual telephone exchange was opened. It served 21 customers in New Haven, Connecticut. Use of the telephone spread rapidly and in 1891, the first automatic number calling mechanism was introduced.

Long-distance service was first made available in 1881. However, the transmission rates were not good and it was difficult to hear. In 1900, two workers at Bell System designed loading coils that could minimize distortions. In 1912, the vacuum tube was adapted to the phone as an amplifier. This made it possible to have a transcontinental phone line, first demonstrated in 1915. In 1956, a submarine cable was laid across the Atlantic to allow transatlantic telephone communication. The telecommunication industry was revolutionized in 1962 when orbiting communication satellites were utilized. In 1980, a fiber-optic system was introduced, again revolutionizing the industry.

Background

Telephones still operate on the same basic principles that Bell introduced over one hundred years ago. If a person wishes to make a call, they pick up the handset. This causes the phone to be connected to a routing network. When the numbers are pressed on a touch-tone keypad, signals are sent down the phone line to the routing station. Here, each digit is recognized as a combination of tone frequencies. The specific number combination causes a signal to be sent to another phone causing it to ring. When that phone is picked up, a connection between the two phones is initiated.

The mouthpiece acts as a microphone. Sound waves from the user's voice cause a thin, plastic disk inside the phone to vibrate. This changes the distance between the plastic disk and another metal disk. The intensity of an electric field between the two disks is changed as a result and a varying electric current is sent down the phone line. The receiver on the other phone picks up this current. As it enters the receiver, it passes through a set of electromagnets. These magnets cause a metal diaphragm to vibrate. This vibration reproduces the voice that initiated the current. An amplifier in the receiver makes it easier to hear. When one of the phones is hung up the electric current is broken, causing all of the routing connections to be released.

Elisha Gray was Alexander Graham Bell's principle rival, first for invention of the harmonic telegraph and then of the telephone. He was a prolific inventor, granted some 70 patents during his lifetime. Born in Barnesville, Ohio, on August 2, 1935, and brought up on a farm, Gray had to leave school early when his father died but later continued his studies at Oberlin College, where he concentrated on physical sciences, especially electricity, and supported himself as a carpenter.

After leaving Oberlin, Gray continued his electrical experiments, concentrating on telegraphy. In 1867, he patented an improved telegraph relay, and later, a telegraph switch, an "annunciator" for hotels and large business offices, a telegraphic repeater, and a telegraph line printer. He also experimented with ways to transmit multiple, separate messages simultaneously across a single wire, a subject that was also engaging the efforts of Bell. Gray prevailed, filing his harmonic telegraph patent application in February 1875, two days before Bell's similar application.

Gray now began investigating ways to transmit voice messages, soon developing a telephone design that featured a liquid transmitter and variable resistance. In one of the most remarkable coincidences in the history of invention, Gray filed notice of his intent to patent his device on February 14, 1876—just two hours after Bell had filed his own telephone patent at the same office. Western Union Telegraph Company purchased the rights to Gray's telephone and went into the telephone business; the Bell Telephone Company launched a bitter lawsuit in return.

Meanwhile, Gray had been a founding partner in 1869 of Gray and Barton, an electric-equipment shop in Cleveland, Ohio. This became Western Electric Manufacturing of Chicago in 1872, which evolved into Western Electric Company, which, ironically, became the largest single component of Bell Telephone in 1881.

The system of transmission presented describes what happens during a local call. It varies slightly for other types of calls such as long distance or cellular. Long distance calls are not always connected directly through wires. In some cases, the signal is converted to a satellite dish signal and transmitted via a satellite. For cellular phones, the signal is sent to a cellular antenna. Here, it is sent via radio waves to the appropriate cell phone.

Raw Materials

A variety of raw materials are used for making telephones. Materials range from glass, ceramics, paper, metals, rubber and plastics. The primary components on the circuit board are made from silicon. The outer housing of the phone is typically made of a strong, high-impact resistant polymer. To modify the characteristics of this polymer, various fillers and colorants are used. The speakers require magnetic materials.

Design

Modern telephones come in many shapes and sizes, but they all have the same general features. They consist of a single handset which contains both the transmitter and receiver. The handset rests on the base when the phone is not in use. They also have a dialing system which is either a rotary dial or a touch-tone keypad. Recently, rotary phones have been phased out in favor of the more useful keypad. To alert the consumer that they have an incoming call, phones are equipped with ringers. A wide variety of specialized phones are also produced. Speaker phones are made to allow the consumer to carry on a telephone conversation without holding the handset. Cordless phones are also available. These models do not require direct connection of the handset to the base. Instead the user's voice is converted to radio waves and then sent to the phone base. This, in turn, gets converted to an electric signal and sent down the phone lines. Another type of common phone is the cellular phone. These phones use radio waves and an antenna system to communicate between phones.

The Manufacturing
Process

Since there are so many different parts that go into making a telephone, the components are typically produced by different companies and then assembled by the phone manufacturer. The main components include the internal electronics, the handset, and the various plastic parts.

Plastic parts

• 1 To produce the plastic parts like the base, handset casing, and push buttons, injection molding is typically done. In this process, pellets of plastic polymer are put into the hopper of an injection molding machine. They then pass through a hydraulically controlled screw and are melted. While the screw rotates, the melted plastic is moved through a nozzle and injected into a mold. Just prior to this injection, the two halves of a mold are brought together to form a cavity which matches the shape of the telephone part. While inside the mold, the plastic is held under pressure for a set amount of time and then allowed to cool. As it cools, it hardens and forms into the shape of the part. This mold is coated with chromium to create a shiny surface.
• 2 After a short while, the mold halves are opened and the part is ejected. The mold then closes again and the process begins again. At this point in process, many of the parts are manually inspected to ensure that no significantly damaged parts are used. If there are damaged parts, they are set aside to be remelted and reformed into new parts.

Internal electronics

• 3 The electronic components of the telephone are sophisticated and use the latest in electronic processing technology. The circuit board is produced the same way that boards are made for other types of electronic equipment. The process begins with a board made of non-conducting material that has the electronic configuration printed on it using a conducting material. This board is then passed through a series of machines that place the appropriate chips, diodes, capacitors and other electronic parts in the appropriate places. To prevent damage caused by dust, the process is completed in a specially cleaned room. When completed, it is sent to the next step for soldering.
• 4 To affix the electronic parts to the board, a wave soldering machine is used. Before being put into the machine, the board is washed to remove contaminants. Upon entering, the board is heated using infrared heat. The underside of the board is passed over a wave of molten solder and through capillary action, all of the necessary spots are filled. As the board is allowed to cool, the solder hardens and the pieces stay in place. This creates an electrical connection between the printed circuits and the components.

Assembly and Packaging

• 5 The individual parts are assembled both automatically and manually. The transmitter and receiver are put together by machines. These parts are then fed onto the main assembly line and inserted into the molded headset. Similarly, the internal electronics, including the touch-tone pad, are inserted into the main housing and attached with screws. The headset is then put on the phone base and the phone chord may also be put on.
• 6 After all of the phone pieces are assembled, the completed phones are put in final packaging. Typically, they are wrapped in plastic and put in boxes. A packaging material such as polystyrene is also included to protect the device from damage during shipping. An owner's manual or other literature is included and the box is sealed with tape. The boxes are stacked on pallets, shipped to distributors and finally, customers.

Quality Control

To ensure the quality of each telephone, visual and electrical inspections are done throughout the entire production process and most flaws are detected. Additionally, the each completed phone is tested to make sure it works. Often these tests are done under different environmental conditions such as excessive heat and humidity to simulate the extremes that are experienced in a real life setting. Plastic parts are given torture tests to ensure they will still function even after a level of consumer abuse. For example, the numbers on a touch tone pad are put under a rubber-finger that taps the buttons enough times that it equals forty years of dialing. Since many of the parts that make up the telephone are produced by subcontractors, telephone manufacturers rely heavily on these suppliers for good quality. To ensure consistent manufacturing, most telephone makers set quality specifications for individual parts that the suppliers must meet.

The Future

Telephone technology is improving rapidly. In the future, cordless phones will be designed to be smaller and lighter. They will have wider transmission and better reception ranges. The sound quality will also be improved. Other technologies that integrate the phone with computers and cable television will be commonplace. Dialing systems will also be improved. In a recent demonstration, one company showed a technology that accepted voice command to dial a phone number.

Where to Learn More

Books

Bigelow, Stephen. Understanding Telephone Electronics New York: Butterworth-Heinemann, 1997.

Noll, A. Introduction to Telephones and Telephone Systems. New York: Artech House Publishers, 1998.

Grosvenor, E and M. Wesson. Alexander Graham Bell: The Life and Times of the Man Who Invented the Telephone. Harry N. Abrams Inc., 1997.

Periodicals

Woolley, S. "Dial tones? No, Web tones." Forbes (January 26, 1998).

—PerryRomanowski