| 摘要 |
PURPOSE:To quickly send a transmission output interruption alarm even if the signal input line of a transmission output control signal is opened by providing a transmission output monitor circuit, a 1st discrimination circuit, a signal interruption detection circuit, a 2nd discrimination circuit and an OR circuit. CONSTITUTION:If the input signal line for the transmission output control signal is opened, a line open detector 18 is operated, interrupts the output from a selector 1A and gives the information to the 2nd discrimination circuit 4. The 2nd discrimination circuit 4 outputs a high level momentarily based on the information, a transmission output interruption alarm is outputted from an OR circuit 5 and the maintenance personnel recognizes it instantly. In applying the open wire detection for the signal line by the 1st discrimination circuit 3, to the discrimination it takes for some time and it is discriminated to use the information representing the presence of an input signal to relieve the defect of a conventional circuit.
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