1. DC style doorbell one for two (transmitter * 1 Receiver * 2)2. The transmitter uses a small 12V 23A alkaline battery used by the receiver 2AA batteries3.38 Visitors ringtones， 3rd volume adjustment4.50 m Accessible from the wireless receiver is suitable for large suites and villas goodsinstallation method:1. Use the word to open the back cover to open the transmitter， mounted on a small 12V battery2. tear double-sided adhesive， the transmitter on the wall standing， or fixed with screws3. The receiver can plug in4. Remote control power: <10mw5. Receive Rated voltage: 50Hz / 60Hz6. The receiver controllable volume: 25-75dB7. Receiver Standby current: <1.0mA8. Receiver plug socket: 220v9. Operating frequency: 315MHz �� 2MHzRemarks:Receiver calls flashing lights design， even if still hearing impaired visitors know when guests come 38 ringtones to choose from， there is always a right for you. Third gear to adjust the volume， do not worry wake the baby to sleep. Comes with adhesive and screws， double fixed， to avoid losing the connotation one 12V23A little battery is not recommended for contact with the metal， may interfere with the audio.Specifications:Transmitter: 3 * 2 * 3CMReceiver: 9 * 6 * 2.8CMRingtones: 16 polyphonic ring tones 38