Signal Corps Field Telephones

Signal Corps pioneering in the design and development of U. S. Army field telephones is discussed. Explanation is given of the military need for the new features and performance improvements desired in field telephones, and of the methods whereby these new requirements were resolved by Signal Corps engineers. In each instance, the Signal-Corps-developed field-telephone sets performed better than contemporary commercial telephone sets. A few of the Signal Corps inventions and innovations have been adopted by the U. S. telephone industry and incorporated into the design of the latest subscribers' telephone sets, whose improved performance is now comparable to that of present standard Signal-Corps-developed field-telephone sets. The new features of the recently developed, fully transistorized, Signal Corps field-telephone set for use with the completely automatic, electronic-switching, military-communication system are also discussed. The novel circuit features of this telephone make it possible, for the first time, to have a subscriber's line carry only voice-frequency currents at voice-frequency communications level.