OPTICAL APPPARATUS FOR INTERROGATION OF THE STATUS OF A SWITCH

摘要

Apparatus for interrogating the ON-OFF status of an electrical switch (31) comprises a semiconductor body (4) containing a PN junction and means (5) for electrically connecting an auxiliary switch (32) couplet to the interrogated switch, or alternately the interrogated switch (32) itself, across the PN junction. Light (7) of a first wavelength incident on the semiconductor body causes light of a second wavelength (11) to be emitted from the body when the switch is open (OFF), whereas no such light is emitted from the body when the switch is closed (ON). Therefore, photoelectric detection of the emission or non-emission of light of the second wavelength from the semiconductor body indicates the status of the switch.