Omnipro II - Sounder with battery backup

[SIZE=10.5pt]Hi all,[/SIZE]
[SIZE=10.5pt][/SIZE]
 
[SIZE=10.5pt]I'm trying to connect a ADT / Elmdene 7422-G3F external sounder to my Omnipro II panel and looking for advice.  [/SIZE][SIZE=10.5pt]I've connected 'normal' two wire sounders before, but this has a battery backup and hold off terminals and "comfort LEDs" to warn-off intruders, so needs a [/SIZE]consent[SIZE=10.5pt] power supply. Anyone know the correct & [/SIZE]recommended[SIZE=10.5pt] way to [/SIZE]connect[SIZE=10.5pt] such a sounder to an omnipro II? [/SIZE]
 
[SIZE=10.5pt]This is as far as I've got, [/SIZE]I've connected:

• [SIZE=10.5pt]the battery to the BATT + & - terminals[/SIZE]
• [SIZE=10.5pt]And constant 12v & Ground to the hold off (H) + & - terminals (which powers the unit and brings on the [/SIZE]
  "comfort LEDs")

If I interrupt the 12v & Ground power again from either of the hold off terminals the siren sounds (powered from the battery) and I can't turn it off without temporarily applying 12v to the Engineers terminal. 
 
The Sounder does have a R- terminal which says is the correct way to trigger the sounder, and if I apply Ground to this nothing happens, but if I temporarily apply +12v to it the siren sounds and I can't turn it off again, without temporarily applying 12+ to the Engineers terminal.
 
Applying Ground to the ST- terminal makes the main alarm strobes come on as expected, and removing the connection makes them go off again.
 
From the above I could get the omnipro to trigger the sounder by using a relay to temporarily apply 12v to the R- terminal, and temporarily apply 12v to the Engineers terminal to turn it off again. But this doesn't feel  very intuitive which makes me think I'm doing something very wrong. Any help gratefully received.
 
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All the best
Dean

Welcome to the Cocoontech DeanG.
 
Looked at the manual for your device:
 
hxxps://www.elmdene.co.uk/product/files/elmdene-product-technical-guide.pdf
 
Never seen anything like this device before.   Looks to me that the engineering terminals are for testing only.
 
[SIZE=15.215px]ENG[/SIZE]
 
[SIZE=15.215px]Engineer: Intended for use during installation/service, applying +12V to this terminal [/SIZE][SIZE=15.215px]will silence the Sounder. This can be linked directly at the Sounder or wired back to the [/SIZE][SIZE=15.215px]Control Panel; note while ENG terminal has +12V applied the tamper circuit is opened to [/SIZE][SIZE=15.215px]ensure this is not inadvertently left connected. On Grade 3: HS, Vertec and Quartz this [/SIZE][SIZE=15.215px]input doubles as a Remote Test Input (RTST), see below.[/SIZE]
 
I would maybe try workbench testing the device shorting out the two terminals required to emit the sounder.  (Ring terminal ?).
 
Here went to el cheapo combo piezo sounder / strobe combinations ($10 USD) for alarm (very loud) and use the old keypads / Omnitouch screens for exterior in/out door sounds for my OmniPro 2 panel.