Abstract: A communication system having an exchange network which can execute a communication procedure necessary for setting of a communication bandwidth with a party variable bandwidth terminal to make the most of characteristic of a terminal which can change its communication bandwidth during communication and to obtain as many call interconnections as possible. The exchange network includes a variable terminal attribute memory device for storing therein the types and ranges of variable bandwidths of the terminals, a bandwidth decision device for determining bandwidths allocated to the respective terminals, and a control data communication device for transmitting at least an allocated bandwidth data to the associated terminal.

Abstract: A private branch exchange having a comparatively small number of ISDN circuits, in the circuit interface a table is provided for the purpose of conversion between a logical channel lying between ISDN terminal equipment and the private branch exchange and one lying between the private branch exchange and an ISDN network. Such a private branch exchange refers to this table to recognize the correspondence of a user packet between ISDN terminal equipment and the private branch exchange to one between the private branch exchange and an ISDN network in order to perform packet switching on the D-channel. The use of this construction eliminates the need of any packet switching hardware, packet switching transmission line and high speed transmission line for communication between divided processors. Therefore, packet switching on the D-channel is possible without hampering the circuit switching performance of current circuit switching equipment.