RL wireless digital door chime model RL-3929 Characteristics of the system device: battery-operated push button a choice of 16 tones simplicity of operation and installation no cable connection required operating range min. 50 m in the open field transmission does not interfere with the operation of other equipment LED optical indicators: power supply and ringing the digital technology applied in the push button significantly extends the battery life modern design low energy consumption push button (transmitter) battery in the set new water-resistant push button