[Ticket Question] Wired door contact compatible with the GD04?

[securitywarehouse]

I'm looking for a wired door contact that is compatible with the GD04. It will be on a shed door.

 

Do you stock a compatible item?

[stuart_mcg]

Okay, a lesson on alarm contacts and circuits. Basic alarm contacts are as simple as a switch. The sensor side (internally) has a small glass bead called a reed switch. The reed switch is a flexible metal leaf that's attracted to a magnetic force. When a magnet is in close proximity of the leaf, then the leaf bends to close the circuit. So, bring the magnet side of the sensor close to the reed, then the circuit is made. Take the magnet away, then the circuit is opened.

 

So, two wires connect to the reed switch. Some sensors provide other 'spare' terminals for tamper loops or balance resistors. But contacts are generally like a switch.

[stuart_mcg]

Looking at the GD04 I thought I'd better add more info:

The GD04 looks for an input to be shorted to ground in order for an activation to take place. Because most contacts are normally closed. That is short circuit when the door/window is closed, then they aren't suitable. You do get normally open contacts, but I haven't seen them on this site. Another solution would be to add a relay to the normally closed circuit.