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infrared:
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basic ir detector/emitter

a very basic infrared detector/emitter circuit

555 timer 40khz IR Oscillator

here's a circuit to oscillate two ir led's at 40 khz (40,000 times a second.)

40khz IR Tester

test a 40khz ir oscillator, and see if your sensor will be able to see it.

ultrasonic:
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ultrasonic switch

this ultrasonic switch consists of two circuits - one is the transmitter, and the other is a receiver. the receiver responds to an ultrasonic signal from the transmitter (40-50khz) and activates a relay.