| 摘要 |
<p>An earth proving device which includes a solid state relay employing a light emitting diode and photoconductor pair operating on low current/low voltage. Operation of the solid state relay is followed by operation of electromagnetically-operable switches which control electrical connections of a power supply to an electrically-operated apparatus to allow passage of a higher current therethrough. Thus, the earth proving device protects the apparatus by first providing indications of the state of the circuit and earth connections to the apparatus with a low current/low voltage sensing signal before the application of power level current and voltage thereto.</p> |
