Impressive collection of parts:
(patress and screws supplied but not pictured)
The part on the left obviously goes on first, and has a 2-pin cam-lock IDC on the back labelled "A" and "B" for the incoming line. The unit is sealed, but multimeter says it's wired like this (so what do you call a BT-style connector with 12 contact positions? Let's say "Fred"):
Resistance measurements between accessible nodes are consistent with the standard master socket line termination and bell circuit, so that's what I've assumed (inside the dotted box).
The 12-position connector (Fred) engages with the filter board, but the pins on the filter board are doubled up, so pairs of pins along each row are commoned when plugged in (although with no matching contacts in the socket - all a bit weird). Three conductors come back from the filter board to a 3-pin cam-lock IDC labelled "2", "3", & "5".
The filter unit has a BT631A phone socket and a RJ-45 modem socket on the front, but also a 2-pin cam-lock IDC on the rear labelled "A" and "B". These bleep out directly to Fred's contact pins from the incoming "A" and "B" lines, and also to pins 4 & 5 on the RJ-45 (other pins appear not to be connected).
Meanwhile, the contacts on the BT631A (for the phone) bleep out directly to Fred's contact pins to the "2 3 5" IDC (corresponding pin numbers, remaining pins unpopulated or not connected).
So, I conclude that the 3-way cam-lock on the front of the rear assembly is a filtered circuit for connecting permanent-wired house voice circuit extensions, and the 2-way cam-lock on the rear of the filter assembly is for hard-wiring an extension cable to a remote modem. Removing the face plate (filter assembly) disconnects everything from the incoming line.
The filter circuit certainly has a lot more components in it, I wonder whether they'll do any good...
!!!!!
