| 摘要 |
PURPOSE:To avoid a fault where an electromagnetic device has overload by cutting off the supply of a drive signal to the electromagnetic device in case the drive signals are generated for a period longer than a prescribed time. CONSTITUTION:In case an up/down counter 2 has a fault and the output is kept at ''1'', a monostable multivibrator MM31 produces a signal with which the level ''1'' lasts for a set time T. Therefore an AND circuit 32 produces a signal of level ''1'' by having the coincidence secured among input signals while the MM31 is producing a signal of level ''1''. This signal drives a motor 4 via a driver 33. The output signal of the MM31 is set at ''0'' after the period T. The circuit 32 is unable to produce a signal of level ''1'' since no coincidence is obtained among the input signals despite generation of a fault which delivers the signal of level ''1'' from the counter 2. As a result, the motor 4 works only for the period T during which the MM31 produces an output signal and does not work any longer. This prevents the overload of the motor 4.
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