| 摘要 |
<p>Photoelectric switch (10) having rectifier (104) for converting received AC voltage to DC voltage, transparent cover (14) having user friendly finger rest surface (24), means for generating a pulsed infrared beam (30) across finger rest surface (24), means (10, 10') responsive to the breaking of pulsed infrared beam (30) by an operator placing at least one finger on surface (24) to actuate a relay (40) to generate an output signal, and means (10, 10') disabling the actuation of the relay (40) in response to operator removing his finger from surface (24) restoring continuity of pulsed infrared beam (30). Photoelectric switch (10) includes fault protection circuits which disable the relay when the AC voltage is below a predetermined voltage or ambient infrared background illumination exceeds a predetermined value. Photoelectric switch (10) also includes circuits for lighting a fault light when the AC voltage is less than the predetermined voltage, ambient infrared background illumination exceeds predetermined limits, and when a contact in the relay welds in the activated position.</p> |
