marsboy receiving set doorbell kits are your best in unit of time life :-RRB- A unbroken design for home and office use. 1 doorbell transmitter 2 plug-in percussive instrument units within 1476ft, lasting connection, lengthened strong operating range, toughened receiving set function. No more of missing visitors. : Maximum receiving set transmit power : 27 dBm Wireless receiver sensitivity : 112 dBm Transmission distance : 1476ft Number of ringtone : 30 Package contents : 1 x Transmitter -LRB- 23A, 12V battery included -RRB- 2 x Receivers 1 x Screw installation kit -LRB- 4 anchors, 4 screws, 1 screwdriver -RRB- 1 x look-alike sided sticker 1 x User enchiridion .