The MERLINTMCommunications System

The MERLIN^TMCommunications System is a family of architecturally consistent small-business communications systems. The architecture is a star configuration with a central 8 bit microprocessor in the switch or Control Module for control of all telephone functions. The telephones and the processor exchange information over a proprietary four-pair protocol in a 24 bit message. In the Control Module, all I/O functions are memory mapped and under software control. The switch is an analog space-division solid-state crosspoint matrix, and the system capacities range from two CO lines and six telephones to eight CO lines and twenty telephones. Unlike many of its contemporaries, this system is designed to be installed, administered, and maintained by customers, although many users can be expected to opt for full-service support. Features and options can be added by a family of plug-in cartridges allowing the whole system to be sold directly from a catalog to a customer with limited training. Another design intent, simplified by stored-program control, is to incorporate many of the more popular and useful call-handling features of larger PBX's. A list of these is given in the Appendix. The stored program containing those features resides in a plug-in cartridge. This article will highlight the electrical and physical design of three of the MERLIN communications systems (CS): models 206, 410, and 820.