Most wire in city telephone cables lies underground in tile conduits and comes into the telephone office through a _cable vault_ in the basement. If the city has more than one central office, _trunk cables_ interconnect the offices. At each telephone office the cables run to the _terminal room_, where their hundreds or thousands of pairs of wires fan out to _terminal blocks_ on one side of a large _distributing frame_. Other wires run from the opposite side of the distributing frame to the switchboard or dial equipment. Cross-connections on the distributing frame bring each telephone user’s line to its proper terminal in the switching equipment. A telephone office is dependent on electric power, both direct and alternating. The direct current comes from storage batteries. These are kept charged by generators driven by the regular current supplied by the power company, which also provides the electricity needed for other purposes. Standby generators, usually driven by gasoline or diesel engines, are provided for emergencies in most large offices and in many smaller ones. Ringing machines generate alternating current to operate your telephone bell and provide the various signals you hear in your telephone receiver. These machines are installed in pairs so that there will be no interruption of telephone service should one machine fail to operate properly. [Illustration: _Technicians check for trouble at a desk in a central office. Preventive maintenance, outside as well as inside telephone offices, helps provide good service._] Preventive maintenance, both inside and outside telephone offices, is vital in furnishing dependable, satisfactory telephone service. Telephone men periodically check the condition of telephone plant. Using steadily improving techniques, they often discover faults or weaknesses and have them corrected before the customer is aware of them. Test desks, where testmen also track down troubles in the telephone plant, are essential to giving good service. These are special switchboards with equipment that enables the testman to diagnose the cause and location of trouble on a customer’s line. Teamwork to serve you well In addition to good equipment kept in good condition all the time, good telephone service depends on capable people who are well trained and skilled in their jobs. [Illustration: _Telephone people strive to make the telephone company a friendly, helpful institution. This young lady is one of the courteous service representatives who assist the customers._]