Feature: 1. Self Generating Wireless Doorbell: No wiring, no battery, one press to convert kinetic energy into electric energy, transmitting wireless signal, no need to worry about changing the battery for the doorbell. 2. Long Distance: Two transmitters and two receivers design, can be used in double door and double decker houses, and can set a separate corresponding ringtone. Strong penetrating power, signal pairing, not worry about connecting with the next door. 3. Multiple Function: Not only a doorbell, but also a pager. When a baby and the elderly sleeping alone, and pregnant women need help, they can press it, effectively protect your family. 4. Sound Light Alarm: When the receiver receives a signal, the sound and light will alarm, convenient for the elderly and patients with ear diseases. 58 songs, 4 level volume can be adjusted to solve the problem of volume. 5. Durable Material: Self powered wireless doorbell with fire retardant shell, black round appearance, beautiful and fashion. IP44 grade sunscreen and waterproof, effectively prolong the service life. Specification: Item Type: Self Powered Doorbell Material: ABS Application: Home, shop, office doorbell or pager Plug Voltage: AC110-240V Type: 2 Transmitters and 2 Receivers Color: Black Transmitters: Power Source: Self Generated Appearance Size: Approx. 63x63x20mm/2.5x2.5x0.8in Ambient Temperature: -20℃ to +60℃ Transmission Distance: Approx. >150m/164yd (open space) RF Frequency: 433MHz Receivers: Power Supply: AC110-240V 50/60Hz Power Consumption: 0.25W Ringtones: 58 Ringtone Volume: ≥90dB Ambient Temperature: -10℃ to +45℃. Package List: 2 x Doorbell2 x Internal Machine2 x Sticker1 x Manual