House Alarm Repair.

Magnetic contacts.

These are very simple. They require no power supply and they fail rarely, moisture is their biggest enemy. The surface mounted is my preferred choice since it’s more reliable and has a large clearance gap (normally around 1 to 1.5 inches).

The flush mounted is more attractive but the gap is much more critical. My problem with these (I used to use them but don’t now) is if the door drops or warps they don’t work. When they do fail you can make a hell of a mess trying to remove them because the wood tends to seal around them.

The roller shutter contact is the same but bigger and much more robust. The aluminium casing is designed to have a car driven over it regularly. These fail very, very rarely.