TIME DIVISION MULTIPLEXING TRANSMISSION SYSTEM

PURPOSE:To easily provide an IO device to a monitor television set side by side by commonly using a transmission line for transmitting composite video signals and performing two-direction communication by switching the transmission line to data transmission systems on both sides during the vertical blanking period. CONSTITUTION:On a host device side, the 1st switching means 31 switches the transmission line 100 to the 1st data transmittingreceiving section 18 from a video signal sending means 30 for a prescribed period after vertical synchronizing signals 72 are sent and, on a monitor side, the 2nd switching means 32 switches the transmission line 100 to the 2nd data transmitting-receiving section 28 from a monitor 29 for a prescribed period after the vertical synchronizing signals 72 are detected. Since synchronizing signals (horizontal synchronizing signals and color bursts) disappear while the switching is performed, a false synchronizing signal generating section 22 generates a false synchronizing signal 74 and outputs the signal 74 to the monitor 29. Therefore, data can be transmitted together with composite video signals 70 in a time division multiplexed state and an input-output device can be provided to the monitor 29 side by side without providing any additional transmission line.