This heavy duty type of metal contact would normally be used on Roller Shutter or Garage Doors. As the magnet side moves away from the switch side the switch opens to activate the alarm. Comes pre-wired with 4 core alarm cable protected by a metal armored outer sheath and supplied with a 6 way low voltage junction box with anti-tamper for connection of the roller shutter to the existing alarm cable. Designed to be added to virtually any WIRED burglar alarm system for example - ADE, Texecom, Eurosec, Scantronic, Ademco, C&K and many others! If you are not sure just ask, we are here to help! Main Features Heavy Duty Metal Construction Normally Closed Alarm Circuit (Going open in Alarm (Magnet Removed)) Normally Closed Tamper Circuit Metal Armored Cable (Approximately.