While testing how to join calls in progress, I learned that if you transfer the call to 700**EXT, you can then call 700**EXT and join your conference. However if you are already in a conference you can transfer the conference to the conference. Is there any way to block this?
Full Scenario:
Consider I have a BLF custom speed dial: 700**123.
While on a call I can press the BLF, which transfers the call to my conference.
I can then place another call and put it in the conference by hitting the BLF. Now the two remote parties are in the conference room.
Now I can join them by dialing 700**123, or hitting the BLF. The BLF is easy so I do that.
Now the three of us are together. Two parties are in the conference, and I have called the conference. If I hit the BLF button _again_, it transfers my call (with 700) to the conference extension (700) and drops me. Now there are 3 parties in the conference: Two external calls + the conference room. At this point any sound starts a feedback loop, as 700 is in the call with 700.
It would seem that if the system blocked the transfer of an extension to itself (at least for this one extension), that would be good and would solve this, right? Are there expected use cases where the conference extension should accept a call transfer for the conference extension?
It is a common enough scenario here with our technicians trying to conference with two outside parties that have phone trees that they complain about this not working with 3CX. When in the conference all keypresses are suppressed so they cannot navigate a phone tree. Putting one party into the conference room, directly dialing and completing the call to a second party, joining them into the conference, and then finally dialing into the conference seems like a winning process. But one accidental extra button press will instantly cause a feedback loop of chaos.
Example of me in a conference: (OK)
Example of transferring the conference to itself: (Remote party hears feedback)
Now me dialing back in to the conference: (Lots more feedback noise)
And finally - the conference still in a call with itself: (The local and remote calls hung up but there is still an active party in the conference)
I don't know how long it will stay like that, I ended the call from the management portal after 10 minutes.
(I actually use 4 digit extensions so my conference extension is 7000, but everything above applies so I explained with the three digit extension to fit the "normal" scheme)
Full Scenario:
Consider I have a BLF custom speed dial: 700**123.
While on a call I can press the BLF, which transfers the call to my conference.
I can then place another call and put it in the conference by hitting the BLF. Now the two remote parties are in the conference room.
Now I can join them by dialing 700**123, or hitting the BLF. The BLF is easy so I do that.
Now the three of us are together. Two parties are in the conference, and I have called the conference. If I hit the BLF button _again_, it transfers my call (with 700) to the conference extension (700) and drops me. Now there are 3 parties in the conference: Two external calls + the conference room. At this point any sound starts a feedback loop, as 700 is in the call with 700.
It would seem that if the system blocked the transfer of an extension to itself (at least for this one extension), that would be good and would solve this, right? Are there expected use cases where the conference extension should accept a call transfer for the conference extension?
It is a common enough scenario here with our technicians trying to conference with two outside parties that have phone trees that they complain about this not working with 3CX. When in the conference all keypresses are suppressed so they cannot navigate a phone tree. Putting one party into the conference room, directly dialing and completing the call to a second party, joining them into the conference, and then finally dialing into the conference seems like a winning process. But one accidental extra button press will instantly cause a feedback loop of chaos.
Example of me in a conference: (OK)
Example of transferring the conference to itself: (Remote party hears feedback)
Now me dialing back in to the conference: (Lots more feedback noise)
And finally - the conference still in a call with itself: (The local and remote calls hung up but there is still an active party in the conference)
I don't know how long it will stay like that, I ended the call from the management portal after 10 minutes.
(I actually use 4 digit extensions so my conference extension is 7000, but everything above applies so I explained with the three digit extension to fit the "normal" scheme)
- 3CX Version: 18.0 Update 4 (Build 965)
- Server OS: Debian 4.19.249-2, Hosted in Azure
