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New Member

ISDN Busy Signal Indicator Question! ?

Scenario : All outbound calls give ringing even when the recipient is known to be busy/engaged. The q931 debug gives this :-

Calling party = 10102 (01524510102)

Called party = 842572 (01524842572) - this line was engaged

Oct 6 12:27:49.455: ISDN Se1/0:15 Q931: TX -> SETUP pd = 8 callref =


Bearer Capability i = 0x8090A3

Standard = CCITT

Transer Capability = Speech

Transfer Mode = Circuit

Transfer Rate = 64 kbit/s

Channel ID i = 0xA98384

Exclusive, Channel 4

Progress Ind i = 0x8183 - Origination address is non-ISDN

Calling Party Number i = 0x0081, '10102'

Plan:Unknown, Type:Unknown

Called Party Number i = 0x80, '842572'

Plan:Unknown, Type:Unknown

Oct 6 12:27:49.491: ISDN Se1/0:15 Q931: RX <- SETUP_ACK pd = 8 callref

= 0xE0C5

Channel ID i = 0xA98384

Exclusive, Channel 4

Oct 6 12:27:52.155: ISDN Se1/0:15 Q931: RX <- CALL_PROC pd = 8 callref

= 0xE0C5

Oct 6 12:27:52.163: ISDN Se1/0:15 Q931: RX <- ALERTING pd = 8 callref

= 0xE0C5

Display i = '*EC*08#*AA*NUMBER BUSY#'

Oct 6 12:27:52.339: ISDN Se1/0:15 Q931: TX -> DISCONNECT pd = 8

callref = 0x60C3

Cause i = 0x8090 - Normal call clearing

Oct 6 12:27:52.471: ISDN Se1/0:15 Q931: RX <- RELEASE pd = 8 callref =


Cause i = 0x8290 - Normal call clearing

Display i = '*AA*CLEARED#'

The provider (Thus) claim this '*EC*08#*AA*NUMBER BUSY#' is standard, but I haven't seen this before (maybe I've never looked!) but my guess is that this is foreign to CM.

Anyone help?

  • IP Telephony
Hall of Fame Super Gold

Re: ISDN Busy Signal Indicator Question! ?


true they are sending 'alerting, but immediately after, disconnect. Is some kind of special number that you are calling ?

For how log it is giving you ringing.

Yes it's kind of non-standard what they do including the display messages, on the other hand it should not influence the CM negatively.

New Member

Re: ISDN Busy Signal Indicator Question! ?


There is no detrimental effect on any calls at all, as far as I'm aware (customers fault) it rings until they give up calling.

This happens to any number they are calling, landlines/mobiles etc (like living in a world where no-one is ever busy! which I like the sound of! haha)

The only issue is that they believe the far end is ringing and available when it's not.


Hall of Fame Super Gold

Re: ISDN Busy Signal Indicator Question! ?

Well you are bringing up a very valid issue and are right in complaining withe the provider.

Only, the trace that you too isn't good to make your point because one way or another, the call is disconnected with some resemblance of a valid reason.

Try getting another trace with a longer time between aleting and disconnect were you canprove that the called phone is not ringing.

New Member

Re: ISDN Busy Signal Indicator Question! ?

Hi Andrew,

I would get back to THUS and ask them why they are sending you an Alerting back. They should be sending a Release\Disconnect with a Disconnect cause of 17(User Busy). The codes they are sending in the Display field would only be relevant if they were interworking with another PBX so you extend some features like camp on etc.

Hope that helps


New Member

Re: ISDN Busy Signal Indicator Question! ?

I have a similar problem and from my investigations on CCM 4.2.3 by default it is set to ignore Progress Indicators attached to Alerting messages. Therefore CM applies ringing when it recieves an alerting message rather than connecting the speech path to and allowing the user to hear the inband audio.

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