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: Doorbells Source: AC,Battery Doorbell Type: Wireless Model Number: A20 Remote Range: 300 meters in open area Waterproof : IP44 Transmitter supply: 23A12V alkaline battery (do not include) Music: 36 ringtones Receiver Rated Voltage: 110-220V Volume: 4 levels from 20-85dB Applicable temperature: -30 Celsius to 70 Celsius Use of premises: Home/Office/Villa/Hotel/Hospital/Apartment colour:black Material:plastic size:Transmitter: 77*46*20mm Receiver: 95*65*24mm Package Contents: 1*Doorbell transmitter 1*Doorbell receiver 1*Double sided tape 1*12 V 23A alkaline battery 1*Screw Only 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.