FYI - Just tried it using a T1 crossover cable, and while the lines showed connection, they showed as disabled on my line console. I couldn't make any calls across them. I tried setting the sync bother to auto and manual with no changes.
I reconnected PRIs, rebooted the system, and tried both options on the sync card again, changing both the timing switches and what line it gets timing from (pri/sec), and nothing changed. Still have echo. Made several calls home, and in most cases I could hear myself, then 2 of the calls my mom could hear herself echo but I could hear it.
One key thing seems to be that when the call is answered, there's a loud PSSSHT noise. That seems to be consistent with the static.
