SIA, Contact ID, 4/2, 3/1

["JohnO" <johno@@&%heathkit##.com>]

Hey guys, it's been about three years since I was here pestering you for
basic info about alarm systems, and our training course needs an update, so
I'm back again. (Good to see you all still picking on each other.... ;-) )

The course I'm working on is based on CompTIA's new DHTI+ certification. One
of the certification domains covers security and surveillance systems, and
one of the sub-domains reads:

Monitoring Formats
        -SIA and Contact ID
        -4/2 and 3/2

I've done a basic google search of this group, and the web, and I haven't
found quite what I need. Or let's put it this way...I have an idea what
these terms mean, but can't find info that helps me understand them well
enough to explain it to someone else. Does someone know of a site or article
somewhere that describes these monitor data formats in basic terms? Your
discussions here in the NG tend towards the pro/con at a professional tech
discussion level, naturally, and I can't follow along with some of that.

Thanks!

-John O
Heathkit Ed Systems