| 摘要 |
An input circuit for conditioning a control signal having a variety of waveforms and voltage levels, comprises a pair of input terminals having a metal oxide varistor connected thereacross. One terminal is connected to the base of a transistor through a resistor, the emitter of the transistor driving an opto-coupler for isolating the control signal from a micro-processor which receives the control signal over an inverter having a Schmitt trigger input.
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