Button telephone system which displays line status information

Abstract

A button telephone system includes a parent telephone set and a child telephone set which are capable of radio communication. In a state in which data communication with a host private branch exchange is made, the parent telephone set is constructed so that it enters a mode in which a public telephone line condition signal sent from the host private branch exchange is converted into a signal adapted for the child telephone set and the converted signal is sent as a line vacant condition display signal to the child telephone set by radio waves. Even in the case where the parent telephone set is connected to an extension telephone line of the host private branch exchange, it is possible to transmit information of the public telephone line condition of the host private branch exchange intact to the child telephone set so that it is displayed in the child telephone set. Accordingly, a user can make signal transmission to a public telephone line after the public telephone line condition of the host private branch exchange is confirmed in the child telephone set.