time compressing multiplexing (TCM)

Time Compressing Multiplexing (TCM) refers to a method for data transmission over two- wire ISDN lines. The method, also known as ping-pong, works in such a way that, for example, a 162 kbit/s data stream is transmitted at at least twice the rate (i.e. 324 kbit/s) first in one direction, then in the opposite direction. So although it is a half- duplex operation, this scheme acts on the user like a full-duplex 162 kbit/s system.