Fortress Security Store (TM) Window & Door Contact Sensor for S02 or GSM Home Alarm Systems
The most likely method of forced entry into a home or office is via a door or window. That's why it's so important to have contact sensors attached to the windows and doors on your home - at least on the ground floor. These magnetic sensors can detect any time a window or door is opened. If the alarm is armed, it'll be triggered - setting off the siren and, in the case of the S02/GSM system will call a sequence of designated numbers until someone picks up. Each pair of sensors requires one 23A battery.
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