QGSTAR Model 504D Portable Wireless Doorbell With 32 songs Door Alarm Simple and no-wire installation desgin avoid trouble when in installation and do not effect decorate environment. Wireless remote control range up to 100m in open air, suitable for home, offices, hotels, etc. Build in anti-interference desgin, avoid the interference between users Easy to install, no wiring required. Doorbell ring sound : 32 melody music songs