Basic Function: 1. Wear the transmitter (smaller one) on the child or the protege and wear the receiver on the parent or the owner. 2. Set a distance by the wheel, when the 2 devices leave each other more than the set distance, the receiver will sound alarm and vibrate to remind the receiver owner. Characteristics: 1. No radiation. 2. Beep & vibration to alarm. 3. Freely set the distance from 0-25M. Specification: 1. Sound: 85DB. 2. Transmitter current: 1MA. 3. Receiver current: 3MA. 4. 1-1 matching, no interference. 5. Frequency: 433.92MHZ. 6. Transmitter:24.5(D)×7(T)mm; Weight:6.5g(battery include); Battery:CR2032×1. 7. Receiver: 60×36×15mm; Weight:35.5g (battery excluded); Battery:AAA 1pc (Receiver's AAA battery is not inclusive in the price.)