An over-door interphone system for telephonic communication between a master station unit inside of a house and a remote station unit outside of an entrance door of the house is provided with a night-vision monitoring device. The night-vision monitoring device has a television camera comprising a solid-state camera sensitive to an infrared light. The solid-state camera is responsible for successfully incorporating the television camera within a less bulky housing of the remote station unit as well as for monitoring the image of a visitor by the camera without being noticed. Also, there can be utilized an illumination device producing an infrared which is hardly perceived by the visitor, ensuring monitoring of the visitor at night without a giving unfavorable impression thereto. The illumination device may be driven to operate for a predetermined period of time starting from the actuation of a calling switch, or a communication interval from the actuation of the calling switch to the hangup of a handset on the master station unit. The illumination device may be also driven in response to the actuation of an illumination operating switch or to a low illuminance level of the object. Thus, the illumination device can be operated with a minimum power requirement. The illumination device is controlled to operate in synchronous with the video signal from the television camera, providing an effective monitoring illumination free from flicker.