asterisk users - Mar 2004 - RING,BUSY,congestion indication on chan_modem

Hello,
I have setup asterisk using an isdn card and i4l.
I can make calls from the pstn to a sip phone via asterisk and vice versa.
Unfortunately I do not get any ring (or busy) tone at my Grandstream, 
when making a call via the isdn card and i4l.
The problem of no ring  tone only occurs in this one direction. The 
other way is okay.
Is this, because in indications.conf German signals are not defined or 
ist this a missing feature of i4l?
I googled and found 
http://lists.digium.com/pipermail/asterisk-users/2002-October/005355.html
which let me believe, the problem has been addressed long time ago.  The 
patch there seems not to be integrated in asterisk, or am I wrong?

Thanks for any answer.
Norbert