Wireless systems.<br>Long receiving distance.<br>Environmental protection and energy saving system.<br>Working frequency: 433 MHZ<br>Buttons/receiving from 40 meters or higher<br>32 songs to choose<br>Emitter working voltage: 12 v battery (battery model: 23 a 12v)<br>The service life of the transmitter: work horse power transmitter 15 or less <br>Weight: 119 g<br>Size (bell): 9.9 x 6.1 x 2.9 cm <br>Size (Buttons): 7.2 x 4.0 x1.9 cm <br>1 x Wireless doorbell <br>1 x Buttons ( battery included )<br>In blister package<br /><img src="http://img6.eachbuyer.com/x22/p96/bt211_4.jpg" />