Wire Line Systems for National Broadcasting

Abstract

The interconnecting of radio broadcasting stations by special telephone lines for the simultaneous broadcasting of radio programs began on a commercial basis in 1923. Today well over 30,000 miles of program transmission circuits are in use in the United States and transcontinental broadcasts by means of such wire lines are a daily occurrence. The paper first states the radio limitations which make wire lines necessary for broadcast coverage of large nations. A map and data are given showing the present broadcasting chains in the United States and indicating the extent of their use. An explanation is given of why program transmission circuits must have transmission characteristics materially different from message telephone circuits and a brief discussion of some of the important transmission characteristics of such circuits, including particularly “frequency range” and “volume range.” The present chains in the United States which are made up almost entirely of open-wire circuits on a voice-frequency basis are briefly described. The manner in which these chains are tested and the way control is exercised are also indicated. To exercise this control requires an elaborate network of telegraph wires now aggregating over 40,000 miles and a corps of special men over 300 in number.