Application: The door/window send a radio signal to the security system installed at your home.You can add up to 30 wireless door/window detectors. When a door/window is open the detector sends a signal to the security system. If the system is not prepared, the security system sounds a warnig signal. Every 90 minutes the detectors send a status report to the security system. The DS18 uses two AAA batteries, normally they last approximatly one year. The DS18 has two terminals where we can connect na extra wired detector (the extra detector must have a NC output).