I tested with the old panel and the A/A1 short did nothing, I also tested with the other panel I have (lets call it the 584c, and the original panel I posted about is the K584c) and there is progress in that with only 1 of my 6 400D KTUs, this one being Issue 15, works partially -- I believe Issue 15 of the 400D is the first to support bridged ringing.

The first 2 slots I have fully wired end-to-end (meaning Cisco FXS port to CO pins on Lines 1 and 2 on Block A of the Amphenol going to the Panels 1 connector) seem to work like this:

- With the FXS port providing dialtone configured as GroundStart (with/without battery reversal enabled) and T/R from the Cisco FXS connected directly to the CO T/R pins on the KSU block (straight through T-to-T R-to-R) the key will light on inbound but picking up a ringing line does not work. Pressing a key and initiating a call call does not yield dialtone.
- With the FXS port providing dialtone configured as LoopStart (with/without battery reversal enabled) and T/R connected straight through to the CO T/R pair on the KSU an incoming call lights the key, and I am able to pick up the call on either key (when using my sad only working 400D KTU moved around across the slots). In this config I'm also able to initiate a call, break dialtone, connect with Cisco Unity and navigate with DMTF, 2way audio. Putting a call on hold fails and drops the call.
- In either configuration I do not see the Interrupter doing anything.
- Fairly certain the power wiring is correct and default strapping is as well, but happy to upload a pic, also the Imgur link in my inital post has pics of the wiring on the initial K584c panel.

It's worth noting this second/other 584c panel is oddly different, although its marked as 584c it has cutouts between pairs of the card-edge connectors so you can see the wiring and pins. The first panel I posted about was labeled K584c (ITT maybe?) and was solid with small cutouts for only the connectors themselves much like many of the pictures I have seen. Whats sketchy about this panel is that there are a few wires that bridge pins and are not within the metal 'legs' that hold the terminal board away from the metal frame that holds the KTUs.

This I'm still looking at:
- re-punching the first two lines/swapping blocks/amp leads
- ground connection resistance measurement (something 0.x ohm?) -- I need to take another look at where exactly the ground goes in this house.
- keeping an eye out for another 584c panel...
- picking up an ITT K400 card or a San/Bar 4000

As always, any input would be greatly appreciated smile