Features: Waterproof transmitter, longer service life. Optimization of circuit desian, power saving & durable. Operating range (open area) is up to 120 m. 16 polyphonic melody/chords 36 music for you to choose. Ordinary household doorbell. As a contact, pager, patient care & other special purposes. Home decoration. Use occasions: Homes, factories, hotels, hospitals, shops, offices, etc. Specifications: Receiver: Voltage range: 220V AV Power; DC 3V/4.5V Working temperature: -20-55℃ Frequency: 315 M Hz/433 M Hz Power dissipation: Standby: 0m A; working: