Apollo23 - Wireless Cordless 38 Melodies Music Remote Control LED Doorbell Door Chime Work Frequency: 315MHz Remote Control /Incept Distance &gt;= 40m(in open air) Work Electricity of the Emitter &lt;= 15mA(20 times a day by calculating, a high quality battery can use for a year) LED Indicator: press the send button, LED indicator light will flash, Emitter work and the receiver receive the order and then send out the beautiful music reminded you the VIP visit, the blue-ray LED of the receiver will regular flash along with the music Music source: 38 songs supply for choice, Use the External button "up/down" to finish. (the music include Asia? Europe? Americas famous songs, also has 10 songs of Arab Music, Concert which the Middle East customers' like).