| 摘要 |
A device on an aircraft is monitored to detect a fault or other change of status of the device 2 in response to which a light source 32 is operated to provide a telltale status indication which can be discerned by a human, status information related to the change of status is also generated, a portable receiver 40 is moved into proximity with the light source 32, and the light source 32 is operated to transmit the status information to the portable receiver 40 via free space by means of modulated light which is modulated with the status information. The change in status may indicate a fault, itself indicated by the signal from a sensor 7-11. The receiver 40 include a photodiode 41 and may de-modulate the light and store or display the status information. The modulated light may form the telltale indication or may be in a different part of the spectrum from the telltale indication. The light source 32 may a light emitting diode. Light guides such as optical fibres 60, 61 may be provided. A further light source 50 and receiver photodiode 51 may provide a return communication channel. |
