asterisk users - Jun 2005 - SIP to ZAP dialout without pre"0" (Asterisk <-> HiCom)

Hi everybody,

I using a (test) asterisk system connected to a siemens hicom via a zap
hfc card.

Incoming and outgoing calls from SIP to ISDN and vice versa work without
problems.

The only problem I have is that the hicom needs a predialed zero to
dialout to the pstn. Right now I configured my asterisk to route all calls
starting with a "0" via ZAP to the HiCom. So I have to dial
"00" to make
calls to the pstn. To call the other (ISDN) hicom users I also need to
dial 0xxxx...

Is there a way to check if an extension exists in the asterisk dialplan
and if not route all calls to the hicom?

I would like to be able to dial my normal ISDN extensions and if the
extensions does not exists in the local VOIP world are routed to the
Hicom via zap. I have 5 SIP phones connected to *, so I?m wondering if
there is a way to let asterisk check if the dialed extensions exists on
the local pbx and if not route the call to the hicom pbx.

right now my extensions.conf looks like:

[isdn-outgoing]
;AMT mit ZAP
exten => _0XX.,1,SetLanguage(de)
exten => _0XX.,2,Answer
exten => _0XX.,3,SetCallerPres(allowed)
exten => _0XX.,4,SetCallerID(${CALLERID}})
exten => _0XX.,5,SetCIDNum(${CALLERIDNUM})
exten => _0XX.,6,CallingPres(03)
exten => _0XX.,7,Dial(Zap/g1/${EXTEN:1},90,tTf)
exten => _0XX.,8,Congestion
exten => _0XX.,9,Busy
exten => _0XX.,10,Hangup
exten => _0XX.,108,Congestion
exten => _0XX.,109,Busy
exten => _0XX.,110,Hangup

[isdn-incoming]
exten => 4445,1,Answer() ;
exten => 4445,2,SetVar(CALLFILENAME=${EXTEN:1}-${TIMESTAMP})
exten => 4445,3,Monitor(wav,${CALLFILENAME},m)
exten => 4445,4,SetCIDName(Hotline - ${CALLERIDNAME})    ;
exten => 4445,5,Queue(101|t|||120)       ; Hotline
exten => 4445,6,Macro(vm,3331)   ;

exten => 4446,1,Macro(exten-vm,2804@default,2804)
exten => 4447,1,Macro(exten-vm,3331@default,3331)

exten => 4448,1,Macro(exten-vm,3001@default,3001)
exten => 4449,1,Macro(exten-vm,3532@default,3532)

exten => 4450,1,Macro(exten-vm,2804@default,2804)
exten => 4451,1,Macro(exten-vm,3000,3000)
exten => 4452,1,Macro(exten-vm,4002@default,4002)
exten => 4453,1,Macro(exten-vm,2000@default,2000)
exten => 4454,1,Macro(exten-vm,2804@default,2804)
exten => 4455,1,Macro(exten-vm,3000,3000)

any hints?

best regards
Michael