The Evolution of Station Carrier and Recent Operating Experience

Subscriber carrier has played an important role in serving sparsely settled rural areas where it was not economical or technically feasible to use voice frequency circuits. For increased usage of carrier in subscriber plant the 1964 Rural Electrification Administration (REA) loop survey [1] showed that several new innovations were needed. Using the loop survey information as a foundation, REA established objectives for a carrier system [2] that could serve much of today's subscriber service needs. This equipment has come to be known as station carrier and is available from seven manufacturers in two major categories. The multichannel systems (four or more channels per system) especially fit the needs of rural telephony, and the single-channel systems are used in both urban and rural systems. The first station carrier was placed in service in an REA-financed telephone system during the summer of 1965. Following this and other successful field trials, the telephone industry has witnessed steady growth in its use. There are tens of thousands of channels in use today in the United States and abroad. The successful operation and rapid growth of station carrier may prove to be the gateway to an all-electronic means of subscriber service. This paper outlines the design objectives of station carrier and discusses how these objectives have been met. The authors also give their evaluation of station carrier performance as observed at several REA-financed telephone companies.