Features and specifications: 1. The button supports up to 20 coins and the receiver supports up to 100 coins. 2. If multiple buttons are associated with one or more receivers in the same system, each button can be set to a different ringtone. 3. Power-off memory function: turn on the device again after power-off, no need to readjust and lock the ringtone. 4. The transmitter does not have a screw chuck design, and it can be waterproof and dustproof without a rubber ring. 5.The transmitter USES a 23A12V alkaline battery ( battery not included). 6. Receiver voltage: 110-220-240V. 7. The receiver is available in a variety of plugs, EU plug, suitable for most countries. 8. Receiving distance: 300 meters in open area. 9.The wireless signal will be affected by obstacles. The more obstacles, the more severe the signal loss. 10. The receiver has 5 levels (can be mute) 0-110db, 60 music to choose from. 11. Size: Transmitter 75 x 51 x 20mm, Receiver 95 x 65 x 24mm. NOTE: The button cannot be placed on an iron door as it will interfere with the signal. How to pair signals 1.Pairing method: press and hold the volume button on the receiver for about 5 seconds (LED is on), release the volume button , then press the button immediately, the signal is paired successfully. How to change and lock the music Press and hold the volume button on the receiver before plugging in the plug. Plug in the power outlet until the receiver light turns on, release the volume button, press the music button to set the favorite music ringtone, press and hold the volume button again until what when the light is on, press the transmitter twice immediately, and the music is locked successfully. Note: Due to the light and screen setting difference, the item's color may be slightly different from the pictures. Please allow slight dimension difference due to different manual measurement.