Issues with T1 interface between Fujitsu F9600 and Asterisk


I’m struggling with interfacing a Fujitsu F9600 PBX to Asterisk (running Trixbox).

We are using a straight T1 tie with e&m wink. Here is my issue:

Calls from the Fujitsu to the Asterisk work fine as long as the call is picked up before the first ring is finished. If the first ring is allowed to happen, the calling handset on the Fujitsu side goes busy.

Calls originating from the Asterisk side ring and answer fine.

Anyone have any clues or hints that might direct my troubleshooting?

Thanks a bunch!