Communication system

A communication system for switching connected communications terminal devices comprising:

• a central module for providing central event-status control and switching, said central module comprising a base unit having an internal bus connected to a central processor;
• a system memory comprised of first and second application-specific intermediate memories wherein said first intermediate memory stores events received from communications terminal devices and events to be sent to the communications terminal devices and information for display signaling and the second intermediate memory stores tone and path signaling information;
• peripheral equipment module control means connected to the internal bus for providing an HDLC-oriented interface for connecting peripheral modules;
• and
• a supplementary unit connected to the base unit, said supplementary unit comprising at least one switching element further comprising means for generating pulses and tones and for synchronization of information processing;
• and
• said system having at least one peripheral module connected to the HDLC-oriented interface;
• the central processor being connected via the internal bus to the peripheral equipment module control means that performs switching and signaling of connected communications terminal devices;
• and
• an ISDN-oriented interface connected to the peripheral equipment control means further connected to subscriber transmission units for connection of additional communications terminal devices.