Product Specifications: Model: Self-powered Wireless Doorbell (No need Battery) Ringtones Available: 38 ring tones Receiver Power: plug-in 100 - 240 V home socket Working Frequency: 433MHz +/- 2MHz Receiving Distance: 100m remote (in open area) 3 Levels of ringing volume (25dB to 110dB) - Just click the button to adjust the volume as needed Product Color: Black, White Working Temperature: -20 to +70 Receiver Size: 110 * 55 * 25 mm Transmitter Size: 55 * 50 * 20 mm