DALLEE #552 OPTICAL DETECTOR UNIT OPTO-DT-1; CLOSE OUT PRICE. Optical detection without interference from ambient light is possible with our OPTODT. Use our single input OPTODT1 to sense any given area using line of sight for 6 feet or more (align diagonally to the track) . The OPTO-DT1 (Item 552) is a detection device in which the output relay (Double Pole Double Throw) is activated when the optical path of an infra-red beam is interrupted. The OPTO-DT has two distinct modes. In NORMAL mode, with the time adjustment at minimum setting, the relay will be activated (on) when the infra-red beam is interrupted and relaxed (off) when the beam is restored. As the time adjustment is increased a minimum (on) time for the relay is established. When the beam is broken the relay is (on) for at least the minimum time period. If the beam remains interrupted beyond the minimum time period the relay stays (on) until the beam is restored. In TIMER mode, when the beam is broken, the relay is (on) for the duration of the time adjustment, then relaxes (off). The relay will not again activate until after the beam is restored which will allow the time circuit to reset. The electronic circuitry must be powered by a "regulated" 12 volt DC supply (see our 12VPS, item #369 ) in order to function properly. Failure to use a "regulated" supply can destroy the electronics.