p5740 wireless portable

Way of transferring wireless bells button reach 100 m number of melodies 3 way of pairing self-learning optical signaling on bell no optical signaling on button yes maximum ring volume of 85 dB possibility to add another button yes, max 3 number of buttons in the package 1 pc auxiliary (replacement) P5740T button waterproof button yes power button 1 × 12 V A23 (included) volume control yes number of receivers in a package 1 pc transmission frequency 433 MHz color green 230 V mai