ltem description from the seller
Kit Configuration:Door Sensor;
Power:9-12V;
Connection Type:Wireless;
Arming Type:Password Keyboard;
Origin:Mainland China;
Radio frequency:433MHz;
beam infrared light:2 led light;
Work Voltage:DC 12V;
Work type:wired / wireless;
Most Suitable Work distance:0-50m;
Length: 38cm
Package: 2pcs* Detectors