Feature 1. 300 meters long distance, adjustable tone can change music, prevent string noise is not wrong, simple installation. 2. Indicator, receiver, volume key, selection key, launcher button. 3. Distance barrier-free 300 meters penetration, strong penetration performance, receiving distance to the Air-to-Ground linear distance can reach 300 meters, note: the actual received signal visual environment changes, different signals due to obstacles are different 4. Easy to install: press the button, ring the bell in the room, the receiver installed in the room can be plugged in, receiver intelligent flash, the bell lights Specifications: Model: A20 Scope of work: 300M Music choice: 36 ringtones Volume selection: 4 tone volume adjustable size. Power supply voltage: transmitter uses a 12V23A battery, receiver: 110/220v Size: transmitter: 7.7*4.6*2cm, receiver: 9*5.6*2cm Scope of application: family business residential areas, office buildings, restaurants, factories and other places. Package Included: 1X receiver 1X emitter 1X double-sided adhesive