SM-226L-3Q Seco-Larm Overhead Door Mount N.C. Magnetic Contact w/ 3 Wires for N.O./N.C. Applications (One Pack)

Has three wires black is Colin plus one for normally open and one for normally closed . Even without instructions . Hook up black plus one other and see if it signals it closed with the door closed .

Not much to say, but its made well, and should last years. As far as wiring, black is common, green is normally open, and red is normally closed. Pretty straight forward...... Well worth twenty bucks......

It works on my garage door. Now I can tell when it is open. Good Product.

Armored cable and included magnet bracket make this switch well suited for garage doors and other applications that may have large gaps when closed. Both normally closed and normally open connections are provided for compatibility with all systems. Ive had one installed for several years with no issues.

Solid piece of work.. was easy to use to set up mu open garage door alarm/ light.

I needed a way to sense the position of my garage door for my remote garage door controller that I am building. Initially thought I could use a simple tilt switch but found it would be more difficult to implement and too bouncy. This is a pretty forgiving switch and works great with my garage door.

Works on my DSC system without any problems.

Unlike the junk brand I ordered first, this one works.

Does what I needed. Has both normally open and normally closed contacts making it perfect for residential/commercial applications as well as automotive security applications.

So, 5 stars for quality, but yikes, $20 for a magnet sensor, so 4 stars for value. Anyway, I bought a Nexx garage door wifi control which is just a repurposed $5 Sonoff control with a very cheap magnetic sensor for reporting door position, but it also has a fairly good app (so you pay for the app I guess). Read the reviews on the Nexx, a large number talk about it working and then not, becaue the position sensor stops reporting correctly. and thats because It needs an 1/8 gap on a garage door. On my wobbly old door youre never going to get that consistency; so Sentrol to the rescue with their 2 inch gap. This sensor is industrial quality. Buy a LeMotech ABS Plastic Dustproof Waterproof IP55 Junction Box, cut the cord on the cheap magnet, and splice it into the Sentrol inside this box. Two day shipping, problem solved. Oh, and use the black and green wires from the Sentrol for this application.