Feature: 1. No Battery Required: Self-generating wireless doorbell, no wiring, no battery, long-distance transmission, two doorbells and one receiver, can be used for front and rear doors. 2. Long operating range: strong penetration, signal matching, don't worry and next to the cross line. Whether you use it in a few rooms, it's still easy to be notified when someone calls from the door. 3. 58 Ringtones: There are 58 ringtones optional, and the built-in speaker can output rich, clear and stereo sound. There are 4 adjustable volume levels, and the flashing light is also easy to notice. 4. IP44 Waterproof: Premium materials to avoid being affected by higher temperatures and interference. Can withstand various extreme weather conditions, suitable for indoor and outdoor use. 5. Used as a pager: It can not only be used as a doorbell, but also as a pager, suitable for babies, the elderly, pregnant women, sound and light reminders, convenient for the elderly and patients with diseases of the ear. Specification: Item Type: Self-Generating Doorbell Material: ABS Transmitter Power Supply: Self-generating Transmitter operating temperature: -20C to +60C Transmitter transmission distance: Open places > approx. 150 m/492 ft Transmitter RF frequency: 433MHz Receiver power supply: AC110-240V 50/60Hz Power consumption receiver power: 0.25W Ringtones: 58 Receiver volume: 90dB Receiver operating temperature: -10 to +45