The doorbell can use in office,home, hospital,factory,restaurant or any where you need it.300 meter receiving distance (In the open area),Stable quality is perfect 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.Type:US Plug,it applies to Canada, India, Japan, Mexico, Thailand, the United States, the Philippines and so on.Brand Name:Type: DoorbellsPower Source: AC,BatteryDoorbell Type: WirelessModel Number: A20Remote Range: 300 meters in open areaWaterproof : IP44Transmitter power supply: 23A12V alkaline battery (do not include)Music: 36 ringtonesReceiver Rated Voltage: 110-220VVolume: 4 levels from 20-85dBApplicable temperature: -30 Celsius to 70 CelsiusUse of premises: Home/Office/Villa/Hotel/Hospital/Apartmentcolour:blackMaterial:plasticsize:Transmitter: 77*46*20mmReceiver: 95*65*24mmPackage Contents:1*Doorbell transmitter1*Doorbell receiver1*Double sided tape1*12 V 23A alkaline battery1*ScrewOnly the above package content, other products are not included.Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.