Distance beeper

[silvermau]

Not sure the terms I need but looking to build two device one transmits that you put on something and the other that starts to beep/buzz when other pass the distance of 10 feet away.  I would even be nice to have it so you can adjust the distance before it beeps.  I know of stuff that beeps when you get to close but trying to make so beep when it gets too far away.  I there something already on the market please let me know.

Thanks

[kumaran1988]

For your information, there are a couple of devices in the market that have a long range hi-fi sensitivity.But they are a bit costly..

[silvermau]

After reading what I wrote I don't think I described it correctly.  Think of this way, (just example) I have a child who I'm taking to the mall I stop to talk to someone and the child see something and wander away before I even had change to notice.  Once the child is say 10 feet away from me the device (size of beeper) starts to play a noise to tell me that child is no longer close to me (like leash with no leash).  I was thinking the device would just have to send a signal out to see/hear the other device which it then does nothing, if don

[Bassanova]

How about just using some kind of RF transmitter?  The transmitter (on you) transmits some kind of pilot tone, or better yet a digital serial number, which the reciever (on the child) recognizes.  It would be easy enough to have the reciever emit some kind of alarm when the signal is too low (i.e. the transmitter is too far away).  And you can just tune the attenuator on the trasmitter to what distance you want on the "leach".

An idea that came to me just now: If you implement some kind of time limited "pause / time off" function, for instance if you want the child to go grab a milk or a loaf of bread at the store, and the child doesn't come back, you could also implement a "locate" button, where the transmitter transmits a command at full strength, forcing the reciever into alarm mode.  The system could have a 10-20 yard range in normal mode, while perhaps a 200-300 yard range in "force alarm" mode.  Just an idea...