Technical help with remote door locking

Can anyone assist me with the details of how the central locking works for having a Cat1 fitted.

My sister had an immobiliser fitted to hers, which also opened the car on one button.
Autowatch 674Ri
Her installer said because it wasn't negative locking, it needed an additional interface.
And it worked well, so I decided to have it done.

I took the car, a 2009, to an installer yesterday, and he confirmed it needed an interface/module to make the central locking work.
He gave up after 2hours as he couldn't find the live, and returned the car.
It was a big operation, with lots of staff, a unit, an office, so it wasn't just one guy without much experience.

I am now speaking with another auto electrician who says it shouldn't be a problem, but he needs to know if it's negative locking or not.
I've told him the other two say it's not, but he wants to be sure.
And is booked up until October before he can look at it - and is 45 minutes away.
He's asked me to:
"check to see if there is a white 12 pin plug in the kick panel with the locking wires in. If so then just need to check if they are neg switching
Should be a Brown/Yellow and a light blue/red wires in there 1 for lock signal and 1 for unlock signal"
I will look shortly, but as I'm not 100% 

He has also said the cat1 kit has a full locking set up rather than just neg, so no extras, module/interface needed.
So I'm not sure why he needs to know about the locking if he seems to think it won't be a problem either way, unless it's for his quote.

Anyone shed any light on any of this - I did expect it to be straight forward as the Jimny is quite a basic car.

Maybe not!!

This is the circuit diagram of the central locking

www.google.com/imgres?imgurl=https%3A%2F...HWZwAw4QMygAegQIARBK

I am not exactly clear on what you are trying to do? Are you trying to replace the Suzuki remote central locking, alarm and immobiliser or just add to it?

If you are trying to replace the Suzuki set up I suggest going to someone who knows how to do it, otherwise you might end up with something not working correctly or something that isn't any more secure than the original system.

Based on the diagram in the link provided by DrRobin, it's negative switching.

 

I eventually found someone who would, more importantly could, fit a Cat1 alarm immobiliser.
After going through a number of installers, a couple tried, and a number of which said outright they weren't sure how to do it!!!
Not sure how true this is, but the guy who did it said because Ghost from Autowatch has become such a big thing, the abilities of the technicians is not that great as it's not difficult to install.