| 摘要 |
PURPOSE:To transmit accurately a call from a slave set to a master set even if a CPU is failed by providing separately a CPU failure detecting circuit and transmitting a call to a call tone generating circuit with priority to attain calling when the call is given from the slave set while this failure detection circuit is actuated. CONSTITUTION:When the CPU6 is normal, a display device Lc1 and a speaker SP are driven. When the CPU6 is failed, since a CPU normal signal which is transmitted from the CPU6 normally for each prescribed time is not transmitted to the CPU failure detecting circuit 10, the CPU failure detecting circuit 10 detects it and becomes operative. Thus, when a call switch 11 is operated and a call detecting circuit 31 is actuated, an output of an OR gate 1B and an output of the CPU failure detecting circuit 10 are applied to a call tone generating circuit 8 through an AND gate 1A to operate the call tone generating circuit 8 thereby outputting a call tone from the speaker SP. |
