PURPOSE: To allow a user to easily identify a telephone set to be used when electrical power is failed by displaying whether or not the telephone set connected to a telephone receptacle can be used during power failure by means of the telephone receptacle.

CONSTITUTION: The telephone receptacle is connected by an extension and control line to the telephone exchange, a speech path between an outside line and an extension or between extensions is formed. Each telephone receptacle is provided with a modular jack M, by which a telephone set commercially available can be connected freely attachably/detachably. Further, a display part 42 displaying whether or not the telephone set to connected in the case of electrical power fails can be used is provided on the telephone receptacle. A liquid crystal display is used for the display part 42. A character part indicating the internal electric power fails is arranged in this display part 42, and the liquid crystal shutter is arranged on the surface to hide the character part by the liquid crystal shutter during operation. When the electric power is failed, the liquid crystal shutter is opened and a character is appeared.