asterisk users - Mar 2008 - overlap calls from NT-BRI timeout problem

Hi,
Iam getting calls from an POTS system on an NT port. Multiport BRI card 
running bristuff 0.3.
From time to time the recognized number is incomplete and dial failed.

Is there any way to increase timeout waiting for called numbers?

Because dialed numbers can be from 3 to 13 digits there is no way to regocnize 
the completeness of the number. Other option switch to en-block dialing is 
not possible because of bad documentation of the old POTS system.

I hear the old telephone provider can validate numbers and so they can avoid 
such problems. I guess I do not get access to this POTS club information.

best regards
Thomas