This has become an
incredibly useful and beneficial thread for me (thanks again to all for invalable contributions) and I really do hope it also helps others too, who may have similar matters to consider. I wish I'd studied electrical engineering at school rather than chemistry or woodwork, it would have been far more useful now I'm into my mature(r) years!
@TonyR - totally agree with you that for a few $/£'s investment in a optically isolated relay it is a better decision than frying an NVR. I'm not sure what a 'dry' relay contact means, but I'm guessing my NVR is solid state?
@wtimothyholman - remiss of me not to have included NVR details in my footer, I've updated this just now - it's an
Dahua NVR 5216-16P 4KS2E (from Andy) and I'm about to check the the spec of the max current output of the Alarm Out port. You are 100% I'm not experienced in electronics/electricty, but willing to spend time working things out, once I've got the gist of things....
@Jessie.slimer thank you for your comment, very helpful - I'm very into Smart Home tech, next on my list of things to install & planned in - so it's possible to link an NVR to a Smartthings hub, is that what you've done?