| 摘要 |
PURPOSE:To issue an alarm, by comparing the sampled hold value with the signal value in the transmission line, and detecting abnormality in the transmitter or transmission line by comparing the variation rate between the two with the set value while holding the previous transmission signal at the time of abnormality. CONSTITUTION:By a sampling signal from a timer 12 which constitutes a sampling device, a contact 13 is closed, and a contact 14 is changed over to terminal (a) side to sample input signals from an input signal line 11 and output through an operational amplifier 16, holding in a hold capacitor 18 at the same time. When not sampling, the contact 13 is open and the contact 14 is changed to terminal (b) side, so that the charge charged in the hold capacitor 18 is discharged, and a signal corresponding to the hold value is outputted from the operational amplifier 16. A comparator-amplifier 19 compares this output with the signal value in the transmission line 11. When the variation rate between the two rises abnormally high, the contact 19b is opened to stop sampling, and an alarm output of abnormality occurrence is issued by closing the contact 19a. |
