Abstract: A multiplexed communication system for automatically setting up a multiplexed call circuit between exchanges upon occurrence of a call only when the multiplexed call circuit is required while otherwise releasing the multiplexed call circuit. The multiplexed communication system includes a plurality of exchanges, each of which includes multiplexing/demultiplexing apparatus for compressing and multiplexing data inputted from first input/output to thereby output the compressed and multiplexed data to second input/output ports and for demultiplexing and expanding data inputted from the second input/output to thereby output the demultiplexed and expanded data to the first input/output port, control information messaging apparatus for messaging control information, first detection apparatus for detecting occurrence of a compressible call, and second detection apparatus for detecting that all the calls connected to the first input/output ports have been released.