| 摘要 |
PURPOSE:To reduce greatly both the labor cost and the time loss by turning off the transmitter power supply after detecting a transmission abnormality between a center device and a terminal device based on a signal produced by branching a part of a sound signal sent to the transmitter from the center device as well as said sound signal which is transmitted from the transmitter and received by a receiver and at the same time transmitting an alarm signal to the center device. CONSTITUTION:A transmission abnormality detecting means 13 detects a transmission abnormality if occurs and applies the output to a relay drive circuit 17 as well as to an alarm signal generating means 14 to turn off a power supply 55 of a transmitter 4. At the same time, the detector 13 switches the connection of a transmission line 47 to send the alarm signal given from the means 14 to a center device 1. The device 1 drives an alarm buzzer 9 in response to the received alarm signal alarms the transmission abnormality. When the transmission abnormality is recovered, the device 1 transmits a power supply ON signal of the transmitter. |
