Interprocess communication system of the MT35 digital exchange

Abstract

The MT35 is a digital exchange. It handles subscribers lines and transit traffic. It features a modular structure based on interconnected terminal sites (TS). Each TS has full call handling capability, and can support up to 1500 subscribers; the overall control is handled by two microsynchronized Motorola M68000 microprocessors. Up to 15 TSs may be point to point connected to form a MT35 exchange. There is no shared memory between TSs: communication is over TDM links (Time Division Multiplex, 2 Mb/s) carrying both data (messages between sites) and digitalized voice. It is a loosely coupled architecture (JEN), as compared to an architecture as CM* (SWA). The overall system operational data, including subscriber tables, equipment configuration, supervision and maintenance data, is handled by the exchange as a distributed data base (BOC, COR). Each TS holds a part of this data base in its private memory: it includes local objects (e.g. equipment or subscriber descriptors) and an image of non-local objects (e.g. routing tables or configuration data). A single special TS, in which telephony equipment is replaced by I/O peripherals, called Management and Maintenance Site (MMS) maintains an up-to-date copy of the data base on secondary storage. It supports operator interface, coordinates update operations on non-local objects, TS programs and data base loading. The execution of a function (e.g. call establishment, operator request, etc.) results in the creation of a transaction, which generally spans over several sites, according to the location of the resources involved (e.g. caller and called party).