To solve the problem that various restrictions exist in installation though a conventional interphone system of a wired type between an interphone unit and an interphone response repeating unit can transmit a moving image.

The interphone response repeating unit 102 located in a house between the interphone response repeating unit 102 and an interphone responding unit 103 is installed at a place near the interphone unit 101. Thus, at a client visiting time, a voice signal and a video signal radio transmitted from the interphone unit 101 are received by the interphone response repeating unit 102. When the interphone response repeating unit 102 receives a signal from the interphone unit 101, its received signal is transmitted by using a radio communication similarly to the interphone responding unit 103 as it is. The interphone responding unit 103 can generate an input sound while the image photographed by the interphone unit 101 is displayed.