Modularly structured digital communications system

A modularly structured digital communications system for connecting terminal equipment having versatile performance features to one another and to public networks, comprising:

• a central communication computer having a system data base and at least one multi-tasking operating system,
• for the administration of a line technology task having device program modules hierarchically subordinated to a line technology task organization program exercising distributor functions as a logical network node, said device program modules, controlling a signalling procedure and a user interface of the terminal equipment associated with types of terminal equipment, the system data base being individually accessible to said device program modules via defined data base access rountines, and said device program modules having a pre-processing program level that evaluates signals output by the terminal equipment according to individual line criteria and converts logical messages of the communication computer into setting data for the terminal equipment and having an interpretation program level that converts signals output by the terminal equipment into logical messages by means of system-associated parameters, and
• for the administration of a switching technology task having switching procedure program modules hierarchically subordinated to a switching technology task organization program exercising distributor functions as a logical network node, the system data base being individually accessible to said switching procedure program modules via said defined data base access rountines, and said switching procedure program modules being structured such independently of the class of terminal equipment and independently of the communications services by forming logical sub-processes of the overall switching process such that, in addition to forming at least one connection handler program module for the control of the set up and clear down of connections, further performance feature program modules for the activation and de-activation of corresponding control procedures are formed, whereby
• the line technology task has an input and output memory administered by the line technology task organization program and operated mailbox-like allocated to it and the switching technology task has an input and output memory administered by the switching technology task organization program and operated mailbox-like allocated to it;
• the multi-tasking operating system forming and administering a program bus structure having a transmission protocol defined with universal validity independently of the communications services and independently of the types of terminal equipment for the messages communicated thereover as a logical network node for the intercommunication of the connection handler program modules and at least a part of the performance feature program modules via the input and output memories of the switching technology task and of the line technology task.