using the telephone

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 The open-wire lines are gradually being superseded by cable construction, either overhead or underground, for two principal reasons.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 more circuits can be accommodated-there is a stand..

The smallest conductor used in standard open-wire telephone circuits is No. 12B and S. gauge. A line of such construction will have a loss of approximately 0.06 db per mile. Cable circuits, on the other hand, make use of conductors not larger than No. 19, and a typical..

A telephone service charges $10 per month plus 15 cents per minute. The table shows the relationship between the number of minutes and the cost. Use the rate of change to identify a linear equation for the data shown in the table. Number of Minutes ( x ) 10 20 30 40 50 Cost in D..

The smallest lasers used for telephone communication over optical fibres have as their active medium a semiconducting gallium arsenide crystal about the size of a pin-hea..

. 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..

They are compounds having the general formula AFe 2 O 4 where A is a divalent cation like Mg 2 + or Zn 2 + . They are obtained from Fe 3 O 4 by replacing Fe 2 + by divalent cations. These belong to a category with a general formula AB 2 O 4 where A is a divalent cation and B is a trivalent..

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 are ordinari..

Applications of Lasers - The development of the laser has opened many avenues of investigation and improved many others. The important characteristics that have contributed to its usefulness in these many areas are tile coherence, monochromaticity and great intensity of its radiation. (i)..