The 1/4" jack is likely the old test port, for when you did not want to disturb tenants, but needed to test for Fire Marshall.

Edwards made the exact same system, as did Simplex, unfortunately, I threw skads of tech manuals away a few years ago in a throwing fit. I may still have some of it though.

I'm nearly certain I have some stuff on your master station, they were called "McCullough Loops" and were nearly bomb proof. I'll look it up tomorrow night, or maybe during the day sometime.

Wife's birthday tonight, Daughter and boyfriend took us to dinner........ I mostly noticed the duct detector light and switches on the ceiling were covered over, the Exit lights were not operational, and a piece of lamp cord running to a hidden fixture..... don't remember what I had for dinner. [Linked Image]