optically coded key

The optical key works as an infrared door opener for house, garage and the likes. Diagram 27. 0 functions as the key. It is a transmitter module which sends out a modulated infrared (IR) beam. The modulating frequency can be adjusted through P1. Diagram 27. 1 is the actual lock (receiver module). It uses a phototransistor to receive the IR beam comi
optically coded key - schematic

ng from the key transmitter module. It compares the modulation frequency of the transmitter beam to its internal frequency. When the two frequencies match, the relay is activated, thereby opening whatever elecric door lock is connected to it.

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