| 摘要 |
A voltage monitoring and indicating circuit for producing an output pulse at an output terminal in response to the loss of a positive dc input voltage at an input terminal. A capacitor is charged during the presence of an input voltage at the input terminal, and a transistor coupled to the capacitor and to the output terminal operates in a non-conducting state so that no voltage pulse is produced by the transistor at the output terminal. In the event of a subsequent loss of the input voltage, the capacitor discharges into the transistor and causes the transistor to operate in a conducting state and a discharge path to be provided through the transistor for the capacitor. As the discharge takes place, an exponentially-decaying pulse is produced by the transistor at the output terminal. The components in the discharge path may take any one of a variety of forms to allow the circuit to produce an output pulse at the output terminal as a result of a loss of input voltage due to an open circuit condition or both an open circuit condition and a short circuit condition.
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