Peter L. Peres email (remove spam text)
Try infrared challenge/response. 5 meters is a problem with RF because it
goes through walls and you can have serious problems with this (hint:
building level/storey height is abt. 3-3.5m, your 5m range will reach up
and down beyond that ;-) ).
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See also: www.piclist.com/techref/io/sensors.htm?key=sensor
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