Found on ebay:
https://www.ebay.com/itm/300951963573

It looks remarkably similar to the factory-wired blocks that would have been located within a Comkey 718, 1434 or 2152 KSU.

That'd be my guess too.

As the bottom of the block suggests. It is a diode matrix block for split ringing for 1A2.

https://sundance-communications.com/forum/ubbthreads.php/topics/7868/1a2_diode_matrix

Scroll down to read Ed's very thorough explanation of diode matrix ringing.

Thanks guys!

Never seen one of those, very interesting.

I've seen blocks similar to that used in nurse call systems

Ed's probably right but I seem to remember seeing something like this on a small motel switch to block LD and prefix's
to only local calls.(been a long time)

They were also used with older Executone systems. Most of the ones I've seen were installed in Social Security offices, so it may have been something the contract holder liked to use.

I was with Executone from 80 - 88 and think I only used them for making a diode matrix with 1A2 bridged ringing. I didn't work too much with their nurse call stuff though. But being that it is a telephone block, I wonder if your SS offices might have had 1A2 systems?

I remember them blocks. Tucked in the back of a 150# cabinet.
75 Pair to run a 20 but set w/add on

Fun Times.


Edited for no good reason