[asterisk-users] newbie: intelligent handling of two ISDN lines (4 B-channels)

[Ekkard Gerlach]

I want to bundle two ISDN-lines (4 B-channels alltogether) with
asterisk. I need it for remote administration of my customers. Sometimes
the 2 B-channels of the first ISDN lines are busy (speech or data 
connection), then asterisk should to take a free channel of my second ISDN
line. 

We need no VoIP. Some tutorials/ manpages for this application available?
Is there a possibility to search within the thread of this list? - I don't
find anything ... 

tia
Ekkard