Self-Powered Wireless Battery-Free Doorbell: No batteries needed, no wiring; easy to install and very eco-friendly. Long Range: Maximum range of 200 meters in open area without obstacles; the effective distance at 3 volume levels allows you to hear the ringtone and answer in time. The wireless battery-free doorbell has 38 different ringtones and 3 adjustable levels to meet your needs. Easy to Install and Use: The transmitter uses two types of installation. Use the included tape or screw to attach the transmitter to the door frame. And plug the doorbell receiver into power to start. What's in the Box: 1 x Transmitter, 1 x Receiver, 1 x Double-sided Adhesive Sticker, 2 x Screws, 1 x User Installation Guide. Our after-sales team consists of experienced, professional, and responsible personnel. They will do their best to solve your problems and let you feel our sincerity and care. Buying our products means choosing security and peace of mind.