No Busy Tone in One Direction

Unanswered Question
Sep 16th, 2008
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Currently I'm having a problem with my voip setup because i don't get busy tone in one direction. I run some debugs like the debug isdn q931 and h225 ans1 and test a good call and bad call. Below is my call flow;

Bad Call:

Phone1(2115)--PBX----ISDN Link-------Bugo-------H323 link---------Fort------ISDN

Link------PBX--Phone2(1994:in use)

Good Call:

Phone1(1991)--PBX----ISDN Link-------Fort-------H323 link---------Bugo------ISDN

Link------PBX--Phone2(2142:in use)

Attached were my debugs output.I hope someone can help me.

Many Thanks,


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A Cisco IP phone (CallManager scenario) or Plain Old Telephone Service (POTS) phone (VoIP Toll-Bypass scenario) does not hear a busy tone or announcement message from the PSTN network. This symptom applies for both VoIP Toll-Bypass calls and IP phone to PSTN/PBX calls. The problem may occour when Cisco VoIP routers/gateways exchange signaling capabilties with the telco switch.

Mhon Baul Wed, 09/24/2008 - 08:43
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Hi Wong,

Do you mean that there is a problem with my signaling between the Cisco router gateway and PBX?. i'm using both isdn switch-type primary-net for the voice port configure in router. Also im just getting this no busy tone in one direction.

Please advised!




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