In a channel expansion communication system for transmitting control data to remotely control a controlled object through a plurality of control channels which are allocated time-divisionally in one frame, the communication system includes an expansion encoder which forms expansion control channels corresponding to a plurality of the control data by timely dividing one of the control channels and an expansion decoder for recovering the incoming control data of the expansion control channels transmitted through the expansion encoder, wherein the control data transmitted through the expansion control channel in one frame is compressed in format while changed control data is outputted first.
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