Q.850 cause 26 Non-selected user clearing
You were one of several destinations offered the call and somebody else answered first. That is all cause 26 means. It is the normal outcome for hunt groups, ring-all groups and calls forked to a desk phone and a mobile app — and it is not a rejection, which is cause 21.
What Q.850 cause 26 Non-selected user clearing actually means
The specification puts it in a single sentence: the user has not been awarded the incoming call. Where a call is presented to more than one endpoint at once, only one can win. Every other endpoint gets this cause to explain why its leg stopped ringing. Nothing declined anything and nothing failed — a race was held and this endpoint lost it. RFC 3398 maps it to SIP 404 Not Found, which is a poor description of what happened and another reason to read the Q.850 value rather than the SIP status when interpreting group calls.
This cause indicates that the user has not been awarded the incoming call.
— ITU-T Q.850 section 6.2.7.1.20
The SIP equivalent of Q.850 cause 26
A gateway translating this cause into SIP reports it as SIP 404 Not Found. The mapping is defined in RFC 3398 section 7.2.4.1.
What causes Q.850 cause 26 on a business phone system
- A colleague answered the group call firstThe everyday case. A ring-all hunt group presents the call to everybody, one person picks up, and every other extension records cause 26. A five-person group generates four of these records per answered call.
- A call forked to desk phone and mobile appWhere one user has several registered devices, the call rings all of them. Answering on the desk phone means the mobile app leg clears with this cause — the same person, two devices, one winner.
- Another user performed a call pickupPickup features let a colleague grab a ringing call from elsewhere. The original destination never gets the chance to answer and its leg is cleared as not awarded.
- A shared line or multipoint ISDN arrangementOn a passive bus or a shared line appearance, several devices see the same incoming call. The device that goes off-hook first takes it and the rest are told they were not selected.
How to fix Q.850 cause 26
- Exclude cause 26 legs from missed call reportingThese are not missed calls — somebody answered. Counting them makes a well-run group look like it is failing, and skews any conclusion you draw about staffing.
- Check the ring strategy if one person always winsWith ring-all, the fastest handset consistently takes the call. If workload is uneven, a longest-idle or round-robin strategy shares it out and the pattern of cause 26 records will shift accordingly.
- Confirm multi-device ringing is intendedIf a user is not expecting their mobile app to ring alongside their desk phone, the cause 26 records tell you it is. Turn off whichever device should not be in the group.
- Only investigate when nobody was awarded the callThe pattern worth attention is every member of a group recording cause 26 with no answered leg anywhere. That suggests the call was withdrawn before anyone could take it, and belongs with the originating side.
Fixing the underlying problem
This page explains the code. These guides walk through the fix in detail.
Questions about Q.850 cause 26
Does cause 26 mean the call was missed?
What is the difference between cause 26 and cause 21?
Why does cause 26 map to SIP 404 Not Found?
Related Q.850 cause values
- Q.850 cause 16Normal call clearing
- Q.850 cause 19No answer from user (user alerted)
- Q.850 cause 21Call rejected
Source. Q.850 cause 26 Non-selected user clearing is defined in ITU-T Q.850 section 6.2.7.1.20 and registered in the ITU-T Recommendation Q.850 (10/2018). The causes and fixes above are drawn from our own experience supporting UK business phone systems.