PCM time multiplex switching station - has selective code transmission and uses zero codewords and free channel code words written into memory

摘要

The PCM time multiplex switching station has a system for switching over from transmitting a zero code word to transmitting a free channel code word in vacant time channels. This is done at the interface between an active switching unit and a replacement switching unit. The zero code word and the free channel code word are received in two immediately following time positions in the switching units (DE1,DE2). The zero code word is written into a given cell of the speech memory of the two switching units. Both the addressing address of the speech memory cell and an instruction are recorded to take effect when switching over from one form of transmission to the other.