Abstract: Irrespective of the distance of a line through which a video signal is taken by the camera of a main entrance station, a satisfactory image having not deterioration but excellent visibility is displayed in a monitor of a residential master station. A distance decision unit of a residential master station for displaying a video signal taken by a camera of an main entrance station in a monitor decides the distance of the line length of a master station line in terms of the voltage drop of the DC power supply fed from a controller to the residential master station. A level compensation unit of the residential master station compensates the level of the video signal in accordance with the decided distance. A distance decision unit of the main entrance station decides the distance of the line length of an entrance line in terms of the voltage drop of the DC power supply fed from the controller to the main entrance station.

Abstract: A doorphone system includes a relay station. A doorphone master station and a relay station are wirelessly connected, and the relay station and the cordless extension master station are wirelessly connected. A wireless communication link between the doorphone master station and the cordless extension master station is established via the relay station. Namely, all of the wireless communication between the doorphone master station and the cordless extension master station is executed via the relay station. The above doorphone system can effectively enlarge the communicatable range between the doorphone master station and the cordless extension master station. By using a cordless phone instead of the relay station, a system formed by combining the doorphone system and the cordless phone can be easily formed.

Abstract: An electric lock device which can be used suitably regardless of an operation mode of a thumb-turn. In the electric lock device, components to be placed at a peripheral part of the thumb-turn are miniaturized by separating a control device and an electric power supply, which require a comparatively large space, from a thumb-turn cover. The electric lock device includes a cover device internally having a motor and a thumb-turn cover, a control device internally having a control part, and a power supply part built-in the control device for supplying power to the control device and the motor. Therefore, the cover device can be more compactified than that of a conventional electric lock device in which the control part and the power supply part are integrally placed with the thumb-turn cover and the motor. The cover device can be attached proximity to a thumb-turn without being protruded from a door.