| 摘要 |
PURPOSE:To omit periodical inspection or the like by providing a central machine with a transmission abnormality detecting means and detecting the abnormality of a communication line or terminal equipment on the basis of a voice signal by the central machine which is transmitting the voice signal. CONSTITUTION:The central machine is connected to the terminal equipment through the communication circuit, traffic information or the like is transmitted as a voice signal from the central machine and the voice signal is retransmitted from the terminal equipment to the central machine. A transmission abnormality detecting means 6 is formed in the central machine, a voice signal obtained by branching a part of a transmission starting signal is supplied from a line 30 to the means 6 and the transmission starting signal from the terminal equipment is applied to the means 6 through a line 31. The signals from the lines 30, 31 are converted into digital signals by processing circuits 18a, 18b in the means 6 and the levels of both the digital signals are compared by a comparator 19. The number of times of coincidence of the levels in the comparator 19 is counted up by the 1st counter 20, the number of times of inconsistency of levels is counted by the 2nd counter 21 and a decision circuit 22 decides whether the transmission is normal or not on the basis of the number of times within a prescribed period in the counters 20, 21. The transmission abnormality is applied to an alarm means driving circuit 23 to inform the abnormality. |
