DIGITAL TELEPHONE EQUIPMENT

PURPOSE:To restore the initial state automatically even in case of runaway of a central processing unit by providing the central processing unit of a digital telephone with a specific signal answering-back means which receives a specific signal from an exchange and reports this reception to the exchange and operating a power supply control means to break the power supplied to the central processing unit when an answer-back signal is not received. CONSTITUTION:A central processing unit 4 controls a channel B, a voice control circuit 7, a display device 3, etc. while decoding a channel D signal, and the specific signal is transmitted to this unit 4 from a specific signal transmitting circuit 11c of an exchange 11 at intervals of a certain time during this control operation. A specific signal answering-back means 4a of a digital telephone 1 returns the specific signal immediately. If it is not returned, the central processing unit 4 is judged to run away, and the power supplied from a power supply circuit 11e to the central processing unit 4 is broken temporarily by a power supply control circuit 11e to set the digital telephone 1 to the power-on reset state.