I was recently working on an Abacus 6 system.

It was using 11 zones, zones 2 thru to 6 were all doubled up.

I assume zone spliters were used although I must confess I never actually found one.

Each of the five doubled-up zones were wired with a single wire going to the A terminal (the A+, COM and T terminals were all unpopulated).

I decided to look inside one or two of the PIRs.

Other than the +VE and -VE (12V supply) connections, there was only one connection to the detector circuit and that was on one side of the TAMPER switch.

The other side of the TAMPER switch and the 2 x ALARM terminals were not populated.

I'm completely baffled, how does this single wire configuration work?

Any help would be greatly appeciated.

The system wired as you describe should not work. Are you sure there were no resistors in the 'unpopulated' terminals?

Each of the five doubled-up zones were wired with a single wire going to the A terminal (the A+, COM and T terminals were all unpopulated).

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Pete, the system should still show a tamper on these zones, surely?

As pete stated.

The detectors are comets and have dip switches in them the address as either 'A' or 'B' i think you only need 5 conections from the panel including power in to the first out to the second.

Cant get comets anymore so you would have to replace any faulty ones with a zone splitter and normal pirs.

Never come across those before, thankfully!

i still can't understand how the Abacus will work with only one wire connected to each zone. Without a link between COM and T the zone should be in tamper?

Yeah, I understand single wire return for an alarm signal, but he states that there is nothing connected to the panel PCB zone terminals, except one wire to A.

Thats right the 12v is connected though and connected at the panel so the circuit is signalled using some sort of common of one or other.

Pete

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Yes, well! I thought I was following this until that....

I'll just jot down 'avoid Abacus' on the front of my manuals folder, probably the easiest way.

lol @ lurch

Anyone give me a straight answer??!!

If there is only one wire going to terminal A of an Abacus zone, the zone will show tamper. Is this right or wrong??

(I'm pretty sure this is right. I know there are weird and wonderful ways to wire them but didn't think that was one of them!)

Edited November 18, 200421 yr by Brian c

If there is only one wire going to terminal A of an Abacus zone, the zone will show tamper. Is this right or wrong??

(I'm pretty sure this is right. I know there are weird and wonderful ways to wire them but didn't think that was one of them!)

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I'm with you on this one Brian, I know how the PIR loop works (sort of), having not worked with this one I don't know, probably something simple and straight forward, like a jumper in the panel!