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A:
A safety edge is a sensor to detect any obstacles when the door is closing and stop the motor drive.
On a ‘remote control’ roller garage door a leading edge safety sensor is a legal requirement in the UK to prevent closure onto any obstacle, usually with a short or full reverse response too.
Safety edge detectors and either a rubber tube with a light beam inside, which if interrupted by the rubber being compressed, sends the signal to stop. Another safety edge uses the same sort of rubber tube, which also acts as a rubber seal, but has metal strips on the top and bottom, so again when the rubber is compressed the strips make contact and send a signal for the electric motor to stop.