Program-controlled digital telephone exchange

摘要

A stored-program-controlled local telephone exchange in which internal connections and conference connections are treated as though they were both a combination of an external connection, namely an originating connection and a terminating connection. This is achieved by providing a virtual route (ETV1... ETV60), which is realized by records in a computer memory and which is linked to a call handler (CR1... CRn) and which, from the aspect of the call handler, behaves as a conventional trunk terminal (ET1... ET60). Alternatively, the virtual route can be replaced with two hardware implemented digital trunk terminals which are mutually connected by means of a physical wire connection. In the case of a conference connection, the conference equipment (MJ) is connected to a hardware implemented digital trunk terminal (ETC) which coacts with the virtual route (ETVMJ1... ETVMJX). From the aspect of the call handlers (CR1... CRn), there is formed a barrier (11) over which signalling takes place in an identical manner irrespective of whether the call concerned is an external call, an internal call or a conference call. A group selector (GS) incorporated in the local telephone exchange is influenced by program logic located behind the information barrier (11), without the call handlers being aware of the existence of the group selector.