Transponder for attaching to objects for identification

摘要

Normally an LED needs to be provided with a voltage supply in order to supply a light output. Here an LED is supplied with light in order to provide a voltage output. The light will be usually monochromatic light and the voltage produced will be in the region of 1 Volt, although this can be increased by using several LEDs. The voltage can be used to re-charge a battery and trigger an alarm or monitoring device, and in this way the LEDs act as a transponder to indicate the presence of vehicle, container at a stage in manufacture or other processing.