... . No batteries, no pollution. No wires, no limits. 20 years service life The world's first batteryless wireless doorbell.No batteries ... -10°C to +45°C-20°C to +60°CRange(Open field)280 metersRF Frequency868MHz/433MHz/315MHzCrosstalk rate1/4,200,000 ... tones Features &benefits280 meters transmission range in the open20 years service lifeSelf-powered transmitter, no batteries or external power required.16 ...