General description No battery is required for this self-generating wireless doorbell, making it a convenient choice for your home. It features two doorbells and one receiver, allowing for use at both front and back doors. With a long working range and strong signal penetration, you can be notified easily when someone is at your door, regardless of the number of rooms in your home. Technical specifications Item Type: Self-Generating Doorbell Material: ABS Transmitter Power Supply: Self-Generating Transmitter Working Temperature: -20°C to +60°C Transmitter Transmission Distance: Open Places > Approx. 150 m/492 ft Transmitter RF Frequency: 433 MHz Receiver Power Supply: AC110-240V 50/60 Hz Receiver Power Consumption: 0.25 W Ringtones: 58 Receiver Volume: ≥90dB Receiver Operating Temperature: -10°C to +45°C Usage 58 ringtones available, with a built-in speaker that emits rich, clear, and stereo sound. 4 adjustable volume levels to suit your preference. Flashing indicator light for easy