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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.



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

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


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


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


—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.


—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.


—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.


—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).

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