Abstract: A digital switching telecommunications exchange handling pulse code modulated information samples in time division multiplex form on incoming and outgoing junctions. The exchange includes a receive interface for each incoming junction and a transmit interface for each outgoing junction and a pair of identical time division multiplex switching networks providing interconnection paths between any incoming junction channel and any outgoing junction channel. Under non-fault conditions exchange calls use indentical paths in each network and the transmit interfaces include error checking and comparison arrangements for each pair of information samples received under fault conditions the transmit interfaces can be arranged to select the non-faulty sample on a per channel basis or can be biased to select one network exclusively.