Service Features and Call Processing Plan

The No. 2 Electronic Switching System performs the functions of a local telephone central office under the control of a stored program acting through data processing, input-output, and two-wire switching equipment. Virtually all the actions of the system are determined by the sequences of instructions coded and stored in memoiy. The No. 2 ESS stored program may be divided into two parts: the call processing programs, which provide telephone service and operational features, and the maintenance and administrative programs, which maintain an operational system in the presence of troubles and diagnose the faulty units. Thus, the purpose of the stored program is identical to the purpose of the central office itself, including the implicit function of assuring dependable service. This paper deals with the service features of No. 2 ESS, the call processing programs which provide these features, and with testing lines, trunks, and service circuits which use the call processing programs. The maintenance and administrative programs, the circuits and the equipment for No. 2 ESS are described in other papers. 1-4 2713