PURPOSE: To use effectively a 64kbps channel by adding an external data switching module and a data multiplexing module to a time division exchange.

CONSTITUTION: A 3.2kbps data multiplexing/demultiplexing circuit 11 multiplexes multiple data to 64kbps data. This 64kbps data is connected to a telephone exchange 20 through an interface line 24 and is multiplexed in a 64kbps multiplexing/demultiplexing circuit 21 and is put onto a highway 22. In the exchange 20, all 54kbps channels where putting the multiple data are multiplexed fixedly to a multiplex interface line 23 and are connected to a memory switch 31 of a data switching module 30. This switch 31 performs switching in units of 3.2kbps. The switch 31 is controlled by a control circuit 34 to perform the multiple data switching processing in units of 3.2kbps.