Evernary dog door bell is easy installation, modern&stylish design .The plug-in receiver: Simply plug it to an AC outlet.The transmitters: Just mount them where you need! They can be placed on the door/floor/wall for easy use with a paw or nose, no damage to the wall. In fact, we even can place it to a small board,and let it laying there by the door or where we liked. When we are training our dog, can place it where needed.You can do your training during feeding time. Put the food outside the door, and then show the dog how to ring the bell. When they do it, praise them and immediately open the door.Put your dog out any time they ring the bell, whether they want to or not! Puppy would ring it and when I'd come over to let him out, maybe he didn't want to go out, just wanted to play. So put them out anyway! If you're consistent about it, they will only ring when they want to go out.Technical Parameters Plug-in Receiver working voltage: 110-260V Transmitter Battery: 12V 23A alkaline battery (included)Working temperature:-30°C ~+70°C Transmitter waterproof grade: IP55 Operation range: 500+ feet (open air) VOLUME: 5 Levels (0-110 dB),unique mute-free mode, giving users a better home experience 55 Ringtones: The pairing method is simple.Users can set any music as doorbell ringtone according to personal preference.Packing List Plug-in Receiverx2Transmitterx2Velcro x2User manualx123A 12V Batteryx2Mini screwdriverx1