TSPS No. 1: Operational Programs

The call processing programs of the Traffic Service Position System provide the logic and control for processing telephone calls. These programs supervise the calls, transmit and receive signals to and from other switching systems, send information to and respond to signals from operators, and record billing details on the calls. The programs that provide these and other functions are described in this article with emphasis on those areas that are new or substantially different from No. 1 ESS. To illustrate how the various programs interact and relate to hardware actions, a coin toll call is traced from origination to completion. At the end of the article some ancillary features are also described because of their novelty or because similar programs have not been previously described in the B.S.T.J. Although the TSPS call processing programs are patterned after those of No. 1 ESS, the nature of the TSPS call dictates a number of changes in program and memory organization. Since TSPS handles toll traffic that enters the system via high-occupancy trunks, a software register is dedicated to each of the trunks to store the billing details on the calls as well as miscellaneous information required in handling the call. The high occupancy of these registers, which tends to minimize the memory-saving advantages of the traffic engineered ESS call registers, plus the simplicity of the control strategy for dedicated registers were important factors in the decision to use this 2625