Interprocessor communication in systems with distributed control

A multiprocessor communication technique, called Sub-Module Interface (SMI) because it enables exchange of information between telephony control units (submodules), was developed for a telephony switching system, thus realizing a distributed control philosophy. In addition to allowing any processor to communicate with any other processor in the system, a variety of devices attached to the SMI can also be accessed by the processors. This paper explains the philosophy and operation of this technique and, based on previous common control concepts in telephony, certain conflicts between these philosophies are noted.