Abstract: In a telecommunications system interconnection is made between a broadband network and a narrowband PABX by an interworking unit providing conversion between the cell based switching of the broadband network and the circuit switching of the narrowband PABX, whereby broadband network users have access to PABX telephony facilities. The broadband network may be ATM based.

Abstract: A control system for a time division multiplex digital switching exchange has a number of telephony groups located on separate shelves which are interconnected by an intershelf bus. The intershelf bus comprises two address buses and a data bus. A common control computer inserts addressing data into two registers in a digital switch controller (DSC) which uses that data to control the transfer of data between telephony groups by way of the intershelf bus. The DSC also includes transmit and receive registers connected to the data bus which allows the transfer of data to and from the shelves and the common control computer. Should the common control computer require to read data from the DSC it addresses the DSC as one of the shelves (i.e., inserts the address of the DSC in the two registers of the DSC) to cause the DSC to transfer or read data to or from the transmit and receive register.

Abstract: An electronic switching system in which digital data is required to be exchanged between two pieces of electronic apparatus such as two telephone subscribers, in which a parallel time division multiplex highway is used to carry the data, the highway being divided into two paths, the data being transferred in both directions during a single time period using the different paths for each direction, identification of the transmitting and receiving parties being by use of two address buses in a single time slot period.