Installing ASG to ericcson MD110

Guys,

I have problems when installing Tenor ASG 200 to Ericcson PBX MD110.

I connect the FXS port to CO port of MD110. It works fine, we can make VoIP calls to other sites.

But after some peaceful time (half-day or a day or so), suddenly, the CO is blocked by itself leaving ASG-200 in open state as if someone is making a call using VoIP.

With console, I can see that it the tenor simply receive signal from CO to open the channel, so the tenor gives dial tone, but no dial number is entered. But it would not close, because it is as if the CO keep hanging open…

If I un-plug the cable, the lines are released, but if I plug the cables back, the CO is still hanging, and I have to move to other available CO.

But after a while, the new CO is blocked again…..

Do you have any ideas why, and what should be done about it?

Thank you…