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. 4. 256*256 different codes. Specification: 1. Sound: 80DB. 2. Transmitter current: 1MA. 3. Receiver current: 3MA. 4. 1-1 matching, no interference. 5. Frequency: 433.92MHZ. 6. Transmitter:33×28×11mm; Weight:10.8g(battery include); Battery:CR2032×1. 7. Receiver: 46×38×15mm; Weight:35g (battery excluded); Battery:CR2032×2 (Price does not include batteries).