Thanks everyone - this has gone on the back burner for a while, I think I need a transformer with more VA... the one I'm guessing the one I have is on the low side, or some kind of relay may be needed.
I will update when I get round to it, trying these, but for now, other priorities 
The front bell (using the nest hello) works like a charm, though in case anyone is looking into that as an option.
Thanks again
I just picked up one of these sensors on ebay the other day and after a bit of tinkering, I managed to get it working in openHAB.
Today I have just changed my Zigbee coordinator as I was having reliability issues, with doing this I have had to re-pair all my devices but I can't seem to pair with the doorbell sensor.
Would anyone have any advice on how to get it back in pairing mode? I tried the tiny button but it didn't seem to do anything, I have now taken the battery out, and on restoring power, it just flashes, which I assume is pairing mode but scanning does not find it!
I hope some has some advice, I can't seem to find any information about it anywhere!
Thank you so much, this bit of the instructions did it 
1. Press and hold the tiny RESET button (next to where the wires attach to the circuit board) while you reinstall the battery.
All working again now. It's a shame the device didn't come with any instructions about this. Your link is very helpful!
It cost a dollar.
I wish it did in the UK, £15 but I feel it's still worth it.
Thanks for the additional documentation. I couldn't find it anywhere and sagebyhughes dot com no longer works.
Dang, at one point I had 96 of these, I threw at least 48 of them away - bought them in an auction for $1.25 for a case of 24 of the them - 4 times. I was buying them for the batteries that work with the iris motion/door sensors.
If anyone wants to buy a few PM me.
Oh, the HOAs from Houston Hell...reknowned.
The stories post H. Harvey were the best.
"Clean that mess up"
...but Sir, the whole Metro is in shambles and the trash hauling is backlogged
"No matter, call in someone from out of town...or we're fining you"
Hi,
this thread has been helpful and has pointed me in the right direction, I think.
I can't make my Sage doorbell sensor work with my Friedland wired underdome bell.
(I'm in the UK.)
Bell works fine, with a regular bell push.
Disconnect bell, Sage works fine.
Connect both... bell works, no Sage reaction.
I now think it's because the transformer (and bell) are 8V. So I guess that when the bell is ringing, there's a sufficient voltage drop to make it too low to trigger the Sage.
Does that sound right?
What are my options? Get a new transformer, and a new bell (hard to find "proper" old fashioned bells that aren't 8V).
Or maybe try the current sensing switch that @chirpy used above?
Thanks!
I will say that the current sensor has been working flawlessly with the modified contact sensor. I think my setup is at 16v at present.
Download the Hubitat app
