The Skylink GM-434RTL Wireless Long Range Household Alert Garage Door Monitor was designed to monitor the status of your garage door and inform you when the door is opened. Remembering to close your garage door can be difficult, especially if your hands are full when you enter the house. But your home can remain safe, thanks to Skylink. The garage sensor included in this kit sends a wireless signal to the receiver to notify you of a status change. When the garage door is opened, the receiver will flash and sound an alert or alarm sound. Be notified of your surroundings! The Receiver included in this kit can monitor up to 16 sensors in 4 zones and is compatible with four different sensors: the Motion sensor (HA-434TL), the Door/Window sensor(WD-434TL), the Water sensor (WA-434TL) and the Garage Door sensor GM-434TL. Expandability has never been so easy. If you are looking for a simple alert or alarm system without having to pay a fortune, Skylink Long Range Household Alert is the way to go! Since 1990, Skylink Technologies has strived to manufacture automated systems that ease your home control. Today, Skylink manufactures and distributes a DIY wireless alarm system with app control capabilities, DIY home automation and garage door openers to assemble your connected home. If you have any questions, call Skylink anytime toll free 1-800-304-1187 or send an email at support@skylinkhome.com.