Long Range Wireless Doorbell IP55 Waterproof - Ultra-long wireless 200M range with waterproof & colorful LED flash light button. Battery Operated Wireless door bells without any cables. The strong and stable wireless signal ensures that you will never miss any visitors even if you are in a big house with several rooms. Sound Loud Enough Wireless Doorbell for Anywhere - 4 Adjustable volume and 40 to 120 dB, 39 optional Ring Tones. Memory function makes the doorbell remember the last ringtone and volume, no need to reset even if after a power outage. Easy Installation Electric Doorbell and Support Expandable - Already paired before factory. Expandable up to 20 accessories. Multiple use for home, office, garage, store, office, apartments, villas, garden, hospital, school the disabled people etc. Battery Powered & USB Powered Receiver - The battery powered doorbell receivers can use battery and USB operated. When the battery voltage is lower than 3.4V, the received will prompt " battery low"; When the battery is low, please plug in the USB powered or replace the battery.