When you pick up your telephone, you have at your fingertips a communication system that is mainly local in its operations. Probably you will use it most of the time to talk to people in or near your own community, but wherever you wish, it can carry your voice across the continent or even across the seas to other countries. The telephone industry in the United States now includes: ■ Telephones serving homes and businesses in 75,000 cities and towns, and more than 3,000,000 telephones in rural areas. ■ A network of wire linking these telephones. About 95 per cent of this wire is in sturdy cables, and almost three-fifths of the cable is underground. ■ More than 25,000 central offices in which telephones are connected by means of switching equipment. Over 9,500 of these offices are operated by Bell System companies. ■ Literally billions of small parts—relays, condensers, resistors, vacuum tubes each carefully designed and finely fashioned so that it will work in harmony with all other parts, anywhere in the country. ■ Radio-telephone links to automobiles, trains, ships, airplanes, and countries overseas. ■ A growing system of radio relay routes used for transmitting both long distance telephone conversations and television programs. ■ Highly skilled telephone people living and working in nearly every American community. The Bell System alone employs about 700,000 men and women, who are busy planning, designing, manufacturing, improving, building, operating—all working to fulfill the traditional telephone policy of providing the best possible service at the lowest possible cost. In the telephone office Every time you make a telephone call—either by dialing or by giving the operator the number—you first reach the _telephone central office_. This nerve center of your local telephone system contains equipment through which your telephone can be connected to any other telephone you wish to reach. In a small community there may be only one central office. In large cities there are many of them, all joined by trunk lines. The term _telephone exchange_ means the whole local area served by one or more central offices. Over four-fifths of all Bell System telephones are dial-operated. Intricate machinery in the central office makes connections by obeying the electrical signals that you send over your line as you turn the dial on your telephone. Before you dial, the equipment in the central office tells you it is ready to serve you by transmitting a “hum-m-m-m” over your line. You should hear this _dial tone_ before you start to dial. The dial tone serves the same purpose as the operator’s “Number, please!” [Illustration: _Telephone company buildings are built to harmonize with surroundings in communities where they are located. A central office in California._] [Illustration: _Another one in Connecticut._] [Illustration: _Testing equipment in a dial central office in a large city._]