Here's how it works:
Put the Transmitter on the person or item to be protected,
If the Transmitter gets out of a 15-25 foot range of your Receiver then the alarm will sound.

Features:
long life CR2032 battery
The receiver measures 2 1/2 in (H) X 1 3/4 in (L) X 3/16 (W)
the transmitter measures 1 3/4 in (H) X 1 1/2 in (L) X 3/16 (W).
Both items combined weigh about the same as 4 quarters The Receiver is the size of a thick credit card the transmitter is about half that size.