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New Member

No busy signal from Siemens PBX

I have a problem whereby two mgcp gateways connects to both the pstn and pbx in resilient mode. All incoming calls from the pstn are forwarded to call manager. If the incoming number is not an ip phone, call manager sends the call back to one of the gateways and onto the pbx. If an ip phone dials a busy pbx extension, it receives a busy signal (q931 debugging at the gateway shows "user busy"). If an external caller dials a busy pbx extension, they receive "call failed" (q931 debugging shows "service/option unavailable"). I think this problem may have started when the gateways were reconfigured from h323 to mgcp.

Any help would be greatly appreciated.



Re: No busy signal from Siemens PBX


If a caller from the PSTN calls the phone on the Siemens and the phone is idel does it ring / get answered? Basically is it succesful?

Which leg of the link shows call failed, the link to the Siemens or the link to the PSTN? In the case of an IP phone calling a busy extension what call type is sent to the Siemens? Is this the same as the type from the PSTN?


New Member

Re: No busy signal from Siemens PBX

Hi Paul,

Thanks for your reply. To confirm, a pstn call to an idol PBX extension is successful.

I am looking at Q931 debug for the Siemens to Gateway leg of the call. I am not seeing call failed at this point but a disconnect coming back from the PBX with cause of "Service unspecified/not available". When I compare the Q931 debug for the ip phone call and pstn call, there is also a difference in progress indicators send to the PBX.

IP Phone:

Progress Ind i = 0x8083 - Origination address is non-ISDN


Progress Ind i = 0x8A81 - Call not end-to-end ISDN, may have in-band info

This makes me think that the PBX is missing a progress indicator value from the pstn call. However, I am not sure how to check or change these values with mgcp.

Any ideas where to go from here?



New Member

Re: No busy signal from Siemens PBX

What was the fix for this?

Hall of Fame Super Gold

Re: No busy signal from Siemens PBX

Sever years old thread, unlikely you will get a response.