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Out of range alarm Answered

I'm working on a project where I need to have a transmitter and a receiver with an alarm, so when they are apart a certain distance the alarm goes off. I need the alarm to be attached with the transmitter not the receiver, where it will be attached to a valuable stuff for example.


1. It's easier to make a disturbance alarm for objects that will be laying around. For example a breakable link when objects are separated. A magnetic link could do this. Or a reed switch and magnet.

2. Although it is possible to make a distance dependent wireless "leash" it isn't easy for several reasons. My car has such a device so as I walk away it locks the doors when I get so far away from the car and unlocks then when I am close. Even in a well funded car manufacturing environment they haven't been able to make this 100% reliable.

3. http://www.circuitstoday.com/simple-proximity-dete...


Why do you want alarm on the transmitter.
How could the transmitter "know" that the receiver is out of range?

This sounds like an existing product. Try searching for 'wireless child leash.'