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In May of 1976, a new Common Channel Interoffice Singnaling (CCIS) system linked together the last new No. 4A toll crossbar office in Madision Wisconsin and the first No. 4 ESS toll office in Chicago, Illinois. This was a major milestone in a long-range program to achieve a nationwide Stored-Program Controlled (SPC) network of stored-program controlled switching offices interconnected by a new high-speed, high-capacity interoffice signaling system, CCIS. The SPC network will provide faster, more reliable communication services. An evolutionary transition to the SPC network is in progress. CCIS is now being implemented in the toll or long-distance network. It will subsequently be extended to Traffic Service Position System (TSPS) units and to Electronic Switching System (ESS) local switching offices to provide customer-to-customer CCIS service.

A new interoffice signaling system known as the Common Channel Interoffice Signaling System (CCIS) has been introduced into the Bell System's DDD toll network. It represents a major step forward in signaling systems by providing high speed data links between processors of stored-program-controlled switching offices to carry all signaling and network control information, completely independent of the communication paths used by customers. As CCIS implementation proceeds it will have an expanding and significant impact on the DDD network system performance due to improved speed of signaling and provision of signals to provide a multitude of new network and customer services. The history of common channel signaling is traced from early mechanical implementation to use of present-day technological advances. The fundamental concepts, basic features, signal formats and system operation are described.

An experimental 150-MC personal signaling system has been set up in New York City to evaluate over-all technical performance and explore subscriber reactions to the system. The system includes pocket receivers equipped with tuned reeds and central office arrangements adapted for direct customer dialing. This paper describes the system in over-all terms, and tells how it was engineered. It also compares this system with the 35-MC systems and discusses traffic and radio transmission problems.

An experimental high-speed signaling system capable of signaling at the rate of 100 decimal digits per second over a variety of existing Bell System transmission facilities is described. This system uses several frequencies in combinations as its code elements. Because the manner of discriminating between different frequencies is significantly different from present-day practice, the system has been called polytonic to distinguish it from existing multifrequency systems. Signal separation in this system depends not on the steady-state response of filters, but on the transient response of simple reactive networks. Discrimination is enhanced by the use of rather precise timing in the signal generating mechanism and somewhat less precise timing in the receiver. A second system, capable of signaling at the rate of 300 decimal digits per second over a more restricted range of transmission facilities, is also briefly discussed.