No. 10A Remote Switching System: Remote terminal firmware

The No. 10A RSS remote terminal (RT) is a part of a distributed telephone switching system consisting of one or more remote terminals controlled by a host ESS via data link communication. The RT is a microprocessor-based peripheral controller acting as an extension of the host network. The RT firmware contains a process-oriented operating system. Ringing and other high-power signals are supplied by universal service circuits used in a time-sharing arrangement. The RT firmware is responsible for scanning lines and reporting supervisory state changes to the host. These changes are reported over either the data link or a channel, depending on the state of the line. If data link communication fails, the RT leaves the normal master/slave mode and enters a special stand-alone mode to provide a POTS-type intra-RT service.