Worn by the child, the cartoon animal-shaped transmitter sends a constant signal to the receiver, which is held by the adult. The signal is adjustable - from a distance of 6 to 30 feet, so when the child goes beyond the set distance, the adult's receiver starts to beep, letting them know that the child is starting to wander off. The channels adjust themselves automatically to alert the proper receiver if more than one adult is in the same area using the Child Guard monitoring system. It uses a 434mhz frequency. The new microchips produced by SMT? technology, also referred to as the IC unit, is wafer thin and performs with superb accuracy and is incredibly reliable. The IC unit is nicely hidden in a small plastic animal (looks like a toy) and can be concealed very easily under a shirt or jacket if desired. The YS-077 includes a parent receiver and, the transmitter is worn around the child's neck. The YS-088 includes a parent receiver, and the transmitter is worn around the child's wrist. Simple and easy to use compact wireless design. Child friendly design - Strategically hidden in a plastic toy looking transmitter. Has a rotating dial that you can adjust anywhere between 6 and 30 feet. Transmitter can be attached by buckle, to clothes, or worn as a necklace. Suitable for indoor and outdoor use. Lithium batteries included. Easy to inderstand instructions.