asterisk users - Sep 2004 - Unable to request channel Zap/r1/...

Hi!

At the moment I am trying to use Asterisks /var/spool/asterisk/outgoing 
folder to dial larger amounts of calls at specific times to realise a 
wakeup call/reminder solution.

The problem is that when I dump more .call files in the spool directory 
the free lines I get many "Unable to request channel Zap/r1/number" 
messages and the calls fail.

The strange thing is that even if I put lets say 30 .call files in the 
spool folder my E1 with all channels in onw group has only 15-20 active 
channels and the rest of the calls fail.

I thought I could dump (just an example) 1000 .call files in the spool 
folder and Asterisk would take as much of them as it can handle. 
Obviously this is not the case.

Does anyone of you have a clue how I could handle this? Can I qeue the 
calls somehow?

Any help is highly appreciated

Christian