Random, Uncommanded Blind Transfers

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Hi Guys

I’ve got a situation where an incoming call originated from a trunk provider will ring in a call center and be answered by an agent.

Usually within 15 seconds of the incoming call being answered, it will randomly blind-transfer to another extension in the same call center.

It is as if Asterisk is mis-reading some noise in-band as DTMF and doing the transfer, or the caller is emitting DTMF to transfer.

An examination of CEL records for the relevant call shows the transfer taking place, but no party (the caller or callee) tried to transfer. The relevant queue application already has only small “t” in the parameter list
(e. g. only let the called user – e. g. my agent inside – transfer the incoming call), thereby preventing the caller maybe emitting DTMF down the line and transferring at their behest.

Yet the random, uncommanded blind transfers still take place, always withing about 15 seconds after call initiation in answering an incoming SIP call.

We’re using YeaLink SIP phones – T21P – got 17 branches, this only happens at 3 of them at random times. Same hardware and Asterisk versions (
at all of them, same dialplans.

Operating over about several years, about 10 000 000 incoming calls handled so far, and this only started happening now… dialplans are untouched for months.

Any ideas, pointers, anybody encountered this before?


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