PURPOSE: To display a video image onto a home use television receiver without the need for an exclusive monitor through the establishment of a coaxial cable plug socket to be connected to a coaxial connector of the home use television receiver by extracting a video signal from a camera intercom and applying amplitude modulation to the signal.

CONSTITUTION: A camera intercom adaptor A allows a call detection circuit 4 to detect a call detection signal and to output the signal through the operation of a call switch SW of a camera intercom D. A call tone generating circuit 5 receiving the signal provides a call tone from a speaker 1 and a camera drive power supply circuit 3 gives a camera intercom driving DC power supply to a pair of lines L1. Thus, a call tone rings, a monitor camera C of the intercom D is driven and the video signal is sent through a pair of the lines L1. The carrier of the video signal is amplitude-modulated by a video amplitude modulation circuit 2 and the result is given to a home use television receiver T through a coaxial cable L2. When power supply is applied to the receiver T at this point of time, the video signal caught by the intercom D is displayed on the receiver T without an exclusive monitor.