Features:  1. First choose the music you want to use.  2. Press and hold the receiver's music button until the receiver rings.  3. Press the transmitter, the receiver rings again, and the music matches successfully.  The doorbell can use in office,home, hospital,factory,restaurant or any where you need it.  If paired with multiple push units in one system, the chime can be set individually for each push unit.  300 meter receiving distance (In the open area),Stable quality is ideal for villas, hotels, schools and other areas.  The button cannot be placed on an iron door because it will interfere with the signal.  Just plug the receiver into an electrical outlet,the push button transmitter can be stick it to the door with provided adhesive tapes.     Specification:  Color:Black/White.  Operating range:300 meters in open area.  Volume:4 levels.  Ringtones:58 pcs.  Transmitter size:77*46*20mm.  Receiver size:95*65*24mm.  Battery type: 23A12V alkaline battery (battery not included).  The receiver voltage: 110-220V.  Receiver Plug Type: EU/UK/US plug.  Waterproof grade: IP44.     Package includeds:  2 x Transmitter.  1 x Button.  1 x User Manual Note: Due to the light and screen setting difference, the item's color may be slightly different from the pictures. Please allow slight dimension difference due to different manual measurement.