Aerb Premium Range Up to 300M/1000 Feet Portable Wireless Door Bell Chime and Push Button W 52 Chimes & 4 Volume Levels (2 Receivers) Color: 2 Receivers Model: Wireless Phone Accessory 1. Work up to 1000 feet maximum (best condition without any obstacles); averagely home 600 feet; 2. 52 chimes to select and 4 volume levels to alert; plenty selections offered; 3. Battery operated transmitter / push button; Wall plugged receiver; Receiver size:3.1*1.1*3.4mm; 4. Newest learning function, which grants random (match up): you can use one transmitter for multi 5. Led flashes on transmitter and receiver for indication purpose; Two screws and one double faced