sixwheeledbeast

If you set most of the options in theme settings to classic it looks fine. Very customisable from the user perspective. Dark mode and mobile OOTB is a great improvement.

Buy sensors with compatible FSL resistors built in if you haven't started already.

This is the thread your looking for. https://www.thesecurityinstaller.co.uk/community/topic/35485-programming-texecom-premier-elite-without-a-usb-com-or-pc-com/ It's TTL at the COM port, a search will find online resources on this topic. As an installer it's not worth the effort to make up these.

For Global tamper you have to break them open to measure and compare to as fitted readings for each pair.... It's a Premier so you could go wire them all FSL/EOL then you can narrow the fault down. It may even fix it if one of the tamper pairs are faulty. Yes you can double check by opening it but that is the Aux Tamper. 10 PIR's on 8 zones is asking for trouble.

What's wired into the AUX Tamper?

I took "home office" as Home Office or a government building. You get what you pay for at the end of the day. If the agreement is to use existing infra, even if you don't recommend it and you have that in writing; that's up to them.

Separate network and unmanaged switches. Consider fibre for backbone. You're removing variables that way. Sharing the sites network will only mean liaising with IT departments and intermittent issues you have no control over. Fine, if your site IT on a job creation scheme not so good for us.

I'd say your either following the defaulting instructions incorrectly or very slim chance the panel is duff. We don't provide defaulting instructions here.

Agreed. Control panel being inaccessible and unserviced is most likely the issue. That's if the system hasn't blown something in the meantime.

BUS detection devices would only be compatible with certain compatible control units and there matching manufacturer. Most modern equipment utilises some data BUS type wiring for the keypads and zone expanders, which I believe is the case for the iON. Essentially each device has an address so they can be identified back at the control and they all communicate and get powered from the same line. Often this is wired as a pair for power and pair for data.

Xenon strobes have ~3Kv driver circuit. 230Vac (mains voltages) while dangerous is considered LV (low voltage) in the grand scheme of things.

The strobe would usually be very high voltage unless it's an LED one...

I would use the existing wiring as a base for a hybrid system myself. Too many times have I seen old systems ripped out and junk replacing it. Yes some of the tatty wiring maybe removed but if the system was in good order at some point it may reduce installation or service costs to reuse some of it. For the more direct questions, yes the alarm is likely to sound if you tamper with it. There is no guarantee that any service/engineer modes would work so expect it to rattle your ears. They're designed to be hard to disable and bring attention to the fact someone is tampering with it, if installed and serviced correctly.

Blown fuse or possibly panel. Check for AUX voltage with a multimeter.

Verisure, Eufy, Ring all junk. Texecom is what I fit but not supported for end user installation. Maybe Scantronic?