Note 1: The welcome doorbell is with Chinese Greeting text. Pls check it clear before you buy . if you mind,pls do not buy it . Otherwise we will not bear any loss cause by wrong purchasing . Pls know that. Note 2: pls know that the welcome alarm is not included any battery or power adapter . Only sell welcome alarm . if you want ,pls buy separate . Item specifications: Power supply : DC 9-15V (battery not included) Detection range: 4-8 m Volume: 4 levels adjustable (Can't adjust volume at alarm mode) Induction method : infrared sensor triggered 3 modes: Voice Alarm Music,at "Voice" mode: Human voice,dingdong,nihao,huan ying guang ling;at "Alarm"mode: keeps you aware of intruders;at "Music" mode: just as a doorbell,with 32 music to welcome your guests Ambient temperature/humidity : -10 -40 5% -95% RH Detection Angle: Horizontal Angle of 110 degrees, vertical Angle of 15 degrees The main function: Automatic body sensing , ultra-long , wide-angle detection. Adjustable direction (with stand). Host built-in speakers, alarm loudness of 75-95 db Installation : No need professional personnel, easy to install yourself Installation height: 1.5m-2.5m Music: 32 music and vocals optional Size: Height 7.5cm Width 8cm , thickness 4.5 cm (with base - base can be flat or fixed on top) Battery: 3 x AAA batteries (batteries are not included) Package Contents : 1*Welcome Alarm Doorbell white color( with retail box），2*Screw，1*Bracket，1*Double-sided Adhesive，1*Block the Cardboard