Astribank one way voice

I installed a Xorcom Astribank to the * server.
When I dial from a pstn line (on the Astribank) to an external number or a SIP or IAX phone, everything works fine.
When I call from an outside line or an internal IAX or SIP phone to a Astribank pstn line, i only have one way voice.
No sound is going to the direction of the pstn.
Anybody an idea what is wrong here?
I use Asterisk@home 2.8, with the Astribank using the 1.2.1 version of Zaptel (delivered on the CD of Xorcom)
I also have a AVM B1 ISDN card.