Abstract: A dual wiring system which has improved easy exchangeability and function expandability of function unit, and is capable of constructing a higher-order system by controlling plural function units in a coordinated fashion. A plurality of base units are mounted in wall surfaces of a building structure, and connected to both of an electric power line and an information line installed in the building structure. A function unit is detachably connected to each of the base units, and provides at least one of functions for supplying electric power from the electric power line, outputting information from the information line, and inputting information into the information line. A control unit is detachably connected to the function unit or the base unit, and controls at least two of the function units connected to the electric power line and the information line through the base unit(s) in a coordinated fashion.

Abstract: A dual wiring system is provided, which has improved easy exchangeability and function expandability of function unit, and is capable of constructing a higher-order system by controlling plural function units in a coordinated fashion. A plurality of base units are mounted in wall surfaces of a building structure, and connected to both of an electric power line and an information line installed in the building structure. The function unit is detachably connected to each of the base units, and provides at least one of functions for supplying electric power from the electric power line, outputting information from the information line, and inputting information into the information line. A control unit is detachably connected to the function unit or the base unit, and controls at least two of the function units connected to the electric power line and the information line through the base unit(s) in a coordinated fashion.

Abstract: Two-wire television interphone system is arranged to discriminate by a line voltage discriminator incorporated in a master device a line voltage variation due to a calling operation on the side of a branch device, to actuate a voltage controller in the branch device to shift the system from standby state to operation state, and to drive a call signal generator in the branch device for actuation of a call signal receiver in the master device. The system is thus made to have a power supply circuit energized for a power supply to the system only when required for effecting the calling operation, talking between the both devices, and so on.

Abstract: A balanced transmission device having a pair of impedance element mutually of an equal value and connected between a pair of connecting terminals and an earthing point of an apparatus for superposing alternating signals on a direct current source and transmitting them through parallel two-wire cables. A transformer inserted as a high impedance source with respect to the apparatus for superposing and the transmitter, whereby the device can restrain any noise influence to realize smooth superposed transmission, with simpler arrangement but without enlarging it.