| 摘要 |
<p>An input protection circuit for an electronic circuit includes a switching means operable between ON state and OFF state for generating input for the electronic circuit, a first circuit responsive to an excess level of input for forming a grounding circuit across a first resistor for draining excess level input, a second circuit monitoring input from the switching means for detecting state of the switching means for producing ON/OFF signal depending upon the detected state of the switching means, the second circuit including a second resistor which forms a series circuit with the first resistor and the switching means while the switching means is in ON state. The switching means is operated to ON position for establishing the series circuit for setting the level of the input at a minimum level and to OFF position for blocking the series circuit for setting the level of the input at a maximum level. The second circuit is set a threshold level to be compared with the input level for detecting state of the switching means, the threshold level being set at a level higher than the minimum level and lower than the maximum level so as to assure detection of the state of the switching means.</p> |
