telephone lines

Telephone Lines - The transmission lines used in telephony are of two kinds: open- wire and cable. The open-wire lines are gradually being superseded by cable construction, either overhead or underground, for two principal reasons. In the first place, many mo..

The transmission lines used in telephony are of two kinds: open- wire and cable. The open-wire lines are gradually being superseded by cable construction, either overhead or underground, for two principal reason..

The chance that any one telephone line is busy at a given moment of time is 0.01. What is the chance that out of 5 telephone lines, less than 3 lines are busy? => 0.048 or .001 or 1 or 0.951..

Telephone Circuits - Two-way operation is essential for satisfactory telephone service, and many of the problems of the industry arise from this fact. A simplified circuit for obtaining two-way operation is shown in the below figure. This is called a local-battery system because..

. Telephone and telegraph wires; audio, video, and radio cables; and the myriad nerve fibers in our bodies are all transmission lines. The interconnections of all electric circuits are transmission lines, and in a broad sense waveguides and optical fibers, and even rad..

A modem (a modulator/demodulator) lets you connect your computer to a standard telephone line so that you can transmit and receive electronically transmitted data. It is the key that unlocks the world of the Internet and its World Wide Web, commercial online services, electroni..

These modems, designed for portable computers, are the size of a credit card and fit into the PC Card slot on notebook and handheld computers. These modems are removed when the modem is not needed. Except for their size, PC Card modems are like a combination of external and internal modems. These d..

. If the mathematical sums do not match, the modems communicate with each other by resending the missing segments of data. Modems also have special circuitry that allows them to compress digital signals before modulating them and then decompressing them after demodulating the signals. The compressi..

In long-distance lines, losses are so high that satisfactory operation becomes impossible without the use of amplification. Amplifiers for telephone service are known as repeaters, and they must of course function in both directions along the line. Repeater stations ar..

. Because of rapidly increasing demands for telephone communications throughout the world, multiconductor copper cables have become not only very expensive but also an inefficient way to meet these information requirements. The frequency limitations inherent in the copper conductor system..