| 摘要 |
PURPOSE:To prevent a video transmission line of a video communication system from being intercepted by a 3rd party by changing the cross reference relation between a channel number and a frequency to be inputted from a system of an RF multiplex signal with a control command. CONSTITUTION:A terminal work station 110 sends a video/sound transmission request to a control work station 101, and the station 101 secures one idle channel of a transmission line. A transmission channel control command is sent to a control section 102 to as to modulate the channel and a content of a transmission channel number register is inputted to a modulation frequency conversion section. Then the conversion section sends the converted frequency to a modulation section 108, and a base band video/sound signal from a video camera 114 is inputted to an input terminal 107, and a channel frequency is modulated. The modulation signal is outputted from an output terminal 109 to a transmission line 112c. Since the control section 102 using the command control signal changes the cross reference relation between the channel number and the frequency, the interception of the video transmission line of a video communication system by a 3rd party is prevented. |
