Securityman IWATCHALARMD Add-on Wireless Door/Window Sensor, White (SM-002M) Add-on magnetic door/window sensor for IWATCHALARM series Works with the host of any IWATCHALARM system Magnetic contact sensor for doors & windows 1 red LED indicator lights when door/window is open Transmits at 433MHz wireless frequency with a distance up to 200ft indoors & 450ft with a clear line of sight