| 摘要 |
<p>A self test circuit (10) for a combustion products detector automatically periodically tests whether the sensitivity of the sensor (12) is in a predetermined range between minimum and maximum sensitivities. Transistor switches (36,39) selectively connect different test impedances across the sensor for respectively simulating two amounts of combustion products, one of which is slightly less than the amount corresponding to the maximum sensitivity level and the other of which is slightly greater than the amount corresponding to the minimum sensitivity level. If the sensor either produces a smoke output signal in response to the first test or fails to produce an output signal in response to the second test, then the smoke alarm is actuated after the tests are completed to produce a unique fault signal, the alarm annunciator (24) being inhibited during the test.</p> |
