SYSTEM FOR FAULT MONITORING AND RECOVERING MAIN CONTROL CIRCUIT OF KEY TELEPHONE DEVICE

PURPOSE:To recover early a malfunction due to the disturbance of memory contents and to maintain the working of a normal state, by monitoring at all times the control data given from a telephone through a main control circuit in a main device, and cutting off temporarily the feed to all telephones when a fault arises. CONSTITUTION:Plural telephones T1-TN are connected in branches to a main device ME via a call line 2 and a control line 3 which are provided between the device ME and telephones. A main control circuit monitors at all times the control data which is given to the device ME from a main control circuit 19 for control of telephones T1-TN. When a fault is detected, a feed control circuit which controls a feed circuit 5 is controlled. Then the feed is discontinued temporarily to the telephones T1-TN. The state of this moment is stored in an RAM of the circuit 10, and the faulty telephone is specified by a monitor circuit 12. Then the control is automatically restarted after resetting the telephones T1-TN to the original state respectively. In such way, the working of a normal state is secured.