Communication system and a private branch exchange to be used in such a communication system.

摘要

An integrated services communication system (1) ISDN in which a plurality of ISDN supported terminal stations (6, 7) can be coupled to an S0 bus (4) coupled to a private branch exchange (2), of which a maximum of 2 terminal stations can be active over B-channels. There is proposed also to connect incompletely ISDN supported terminal stations (8) to the S0 bus (4), which stations have many non-ISDN supported features, there being investigated on line cards (9, 10, 11) which type of terminal station is connected. On the basis of a Terminal Endpoint Identifier (TEI) in a layer-2 message, either a standard ISDN protocol is handled from layer-2 onwards, or a firm-owned protocol. <IMAGE>