Four-wire switching of junctions in tdm pcm switching centers under stored-program control

Claim 1

In a circuit arrangement for telecommunication systems for transmitting pulse code modulated signals having switching centers controlled by a store program central control means, said switching centers being interconnected through trunks having at least four wires, each said trunk being a carrier for a number of time multiplex communication channels, communication links being formed thereover, each having an incoming and an outgoing time multiplex channel, said time multiplex channels carrying additionally timing and synchronizing signals, and including first storage means for storing information arriving on said trunks during a pulse frame having a duration corresponding to a sampling period, and further including second storage means controllable by a line selector means for controlling the spatial and time coupling of said communication channels for transmitting the signals in one of said incoming time channels to an outgoing time channel in accordance with the desired route, the ones of said channels connected using spatial coupling having outputs connected to control inputs of spatial crosspoint switching means, the ones of said communication channels connected using time coupling having outputs thereof connected to a storage for effecting write-in in the case of outgoing communications and read-out in the case of incoming communications, the improvement comprising: a plurality of through-connecting means, one of which is allocated to each said trunk including third storage means for incoming and outgoing communication routes, and third storage means being coupled to said time coupled channels, decoupling means for separating timing frequencies in said switching center from clock frequencies appearing on said incoming, time coupled channels, and monitoring means for controlling said synchronizing signal, said trunks being connected to said switching centers as to have direct access to said spatial crosspoint switching means, said second storage means being controllable by said line selected means for spatial and time coordination of said crosspoint switching means, individual storage locations in said third storage means being allocated individually to said communication channels.