OK, looks like my previous drawing is still not right then - but your images make it crystal clear what to do. Thank you. You are a true gentleman.
I think if I had engaged my brain, I would have realised that its NC in use, and then the penny would have dropped where the 4.7k needed to go.
Its an identical set up to my door contact input.
The relay is equivalent to the magnetic reed switch. The momentary enablement of the PGM output and subsequent opening of the circuit, is equivalent to the door opening.
I don't know why I confused myself so much. Embarassed that I put the resistor in that drawing above on the 12v feed into the relay... *sigh*. Misunderstood your term "across closed relay" - but completely makes sense now.
Thank you again. I think I am seeing it clearly now, including all the why's and the hows.
I'll copy what you did and just ordered a similar relay + board from RS.
One thing I'll need to check is that I can remotely silence, reset/re-arm, etc... without having to do so via the panel.
The aim is to scare off anyone snooping around, but then leave the system armed in the usual way. No doubt its all doable. Continuously impressed by this systems capabilities. As I said, I'm just a home DIYer. Hats off to you sir.