benefit to pull-up resistors?

[anuaimi]

I've replaced an old DSC with an UNO board and everything works, which is great. One thing I had to do was turn off the need to have pull-up resistors on each zone as my old system didn't have them.

My question is whether there is any benefit to adding a pull-up resistor to each zone? If not, why is the default to assume they are there. Also, if there is a benefit, should I add them to all zone types (motion, door sensors, water, etc) or only certain ones. I think the key issue is I don't understand when one is needed.

thanks

[GrandWizard]

They are not "pull-up" resistors, they are called end-of-line (EOL) resistors. They allow a security system to monitor the zone for tamper and/or fault.

They are installed in parallel with the NC or NO zone and allow the panel to detect if the zone wire is cut. They are obviously placed at the far-end of the circuit to provide this supervision.

They are the default as they are required for ULC installations but in reality, almost nobody uses them.

[anuaimi]

ah, very helpful. thanks