| 摘要 |
PURPOSE:To shorten the testing time of a safety circuit while keeping the noise resistance of the safety circuit by setting or switching the counting time of a timer means by an external signal. CONSTITUTION:A test shortening line 11 is controlled to LOW at testing time. The output of a comparator 108 is HIGH and a transistor 133 is turned on and a transistor is turned off at the testing time, a current flowing through a resistance 13 charges a capacitor 134, and the transistor 137 is turned on. Therefore, an abnormal state is set in a flip-flop 109, and a relay is cut off. A time constant with respect to the capacitor 134 in this condition is a product of the resistance value of the resistance 13 and the capacity value of the capacitor 134. The resistance value of the resistance 13 is made to be small enough in comparison with that of the resistance 135, so that the time constant at the testing time becomes small, and that the relay is cut off can be rapidly confirmed. |
