Flash button change to blind transfer


I need translate flash button from ip phone to blind transfer feature, this possible ?

Can you program the button on the phone. If not, but it is sent as a telephony event, you will need custom coding (possibly AMI) to detect the event and trigger appropriate actions.

I’m curious… what IP phone are you using that has a flash button? People have inquired about that in the past but I wasn’t aware of a model that actually had one (some softphones do).

Normally its happen with Gateways SIP (FXS) , and ip phone with flash button.

Yes, I know it can happen with analog gateways… but can you name a specific IP phone model that has a flash button?

I saw one on Grandstream Budgetone 100. I would assume models 101/200/201 work same way. I was working (not “for decoration”) but I’m not 100% sure if this was RTP or SIP INFO. I believe it was RTP but I don’t have this phone now.
I saw it also working on some old, cool looking Aastra, but I can’t recognize the model now and I’m not sure if this was separate physical button or if was an option for “BLF”. I think this was 6757i and Flash is listed in manual for this series (it might be actually both 6700i and 9000i) as a softkey function.

button “Transfer” the same function from flash button


Transfer on SIP phones generally initiate a SIP transfer sequence, which Asterisk will honour, and does not send a hook flash telephony event.

when pushed “transfer” button, the Ip phone send a signal and asterisk put call in hold, this signal I’d like change to feature “atxfer”.

Phones differ in whether they do a true blind transfer, or an automated attended transfer. The latter sounds more like what you are describing. The sequence for that is:

Send Re-INVITE (or UPDATE), with SDP indicating a=sendonly (or the older method of c=, which causes Asterisk to put the caller on hold. This step is not strictly necessary for a successful transfer.

Start a new call to the target phone number, as a second line call.

When that callee answers, send TRANSFER/Replaces on side or the other, to instruct the PABX to connect the two calls together.

Wait for the PABX to send BYE, to close the two calls on the phone.

True blind transfer is easier; there is less point in putting the original on hold. The phone simply collects the destination number, then sends a simple REFER, to instruct the PABX to actually do the transfer.

None of these involve sending telephony event 16 (hook flash), as RTP, or in an INFO request, to the PABX.

Any change has to be done in the phone, as, with the first method, Asterisk has no idea that a transfer is coming up until it gets the REFER/Replaces. It looks just the same as a second line enquiry call.

If what the subject is really trying to say is Attended Transfer button change to Blind Transfer, for the reasons given above, that an only be done in the phone. From Asterisk’s point of view, it sees a hold for a second line enquiry, not a transfer, until completion of the transfer is requested.

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