Radio lines (most common analog ones are usually labelled RTNA or RT for *really* old ones) are used extensively by police, fire department, government entities etc.

They come as analog and digital, 2-wire and 4-wire, terminated on anything from RJ11 to a smart jack. Pick your poison, so to speak...

In the old days, one used an Ameritech (I believe) test set to work head-to-head with a tester swapping tone etc. Nowadays, there's a module for JDSU HST-3000 that does the same thing.

While they're essentially a point-to-point circuit, they *can* be a pain to properly provision and test.

Most of the people who knew how to provision these - or test them - have retired, especially with last year's enhanced buyouts. I can't tell you how many times - after spending an hour or more on hold to reach the test bureau - I was told to leave a reach number and that someone would call me when they locate a tester who knows (more likely remembers) how to work on these. Kid you not.

My experience - limited to the boroughs of NYC - is that these things always terminate at weirdest possible locations where no one would find you for days - possibly weeks - if you were to fall down the stairs or suffer a heart attack.

The good news is that most people never get to work on them unless they're employed by LEC or a government entity of some kind.

"...Time moves slowly and it goes so fast..."

(Sandy Denny)