We have 2 Adtran TA1500 shelves connected back-2-back via T1 thru 2 Cisco 3945 ISR's.
I can send a 1khz test tone from an E&M card on shelf A to B...no problem.
But when I try to send the tone in the opposite direction (i.e. shelf B to A) the test tone will not appear on the corresponding E&M card on shelf A.
The Adtran E&M cards are configured for 4-wire type 2 operation and the signalling works fine in both directions.
Let me know if you need more information as to why I can only get the test tone thru in one direction.