asterisk users - May 2006 - Extension '' in context 'whatever' from '123456789' does not exist.

Hi list!

I have a Legacy PBX hooked up to one port of a TE210P. One is connected to 
I want to use the PBX for incoming and outgoing fax.

I managed to get incoming working but I don't understand how to feed calls
from
the PBX into the FreePBX setup.

It seems that when you press zero on the Legacy PBX the PBX just switches over 
to the PRI to pass each digit nicely one by one as it is received to the 
PRI.

When I press zero for an outside line on a legacy phone I immediately get 
this error message :

!! Unexpected Channel selection 3
-- Extension '' in context 'legacypbx' from '(the number of
the
phone on the pbx)' does not exist. 
Rejecting call on channel 0/31, span 2


legacypbx is the context I put on the port connected to the Legacy pbx:

zapata.conf :
group=1
context=legacypbx
switchtype=euroisdn
overlapdial=yes
pridialplan=unknown
prilocaldialplan=unknown
signalling=pri_net
echocancel=yes
echocancelwhenbridged=no
channel => 32-46
channel => 48-62

Does anyone have an idea how to solve this?

Basically I want Asterisk to accept the call from the PBX. Can I set the 
extension that * is expecting hard in a config file and also have asterisk 
wait till all the digits have arrived and then dial the number?

Basically after pressing 0 I want to feed the call into the standard dial 
plan.

Many thanks for any hints / pointers!

Remco