[Asterisk-Users] Supervised transfer (almost) with GS phone

[Stephen R. Besch]

I have now tested a (previously suggested) method for doing supervised 
transfers using the Grandstream SIP phone. It isn't perfect, but it 
works and is very functional. Here are the steps:

1) A call comes in that you want to transfer

2) Flash once. This switches to the 2nd line and puts the caller on hold.

3) Call the party to which you want to transfer the call.

4) Arrange the transfer and have the person to which the call is being 
transferred hang up. Incidentally, while it may be obvious, it is still 
worth mentioning that before they hang up, you can switch back and forth 
between the two parties an indefinate number of times.

5) WITHOUT HANGING UP, press the flash button again. This switches you 
back to the caller.

6) Inform them of the transfer.

7) Press the transfer button and enter the transfer phone number. (This 
starts a simple blind transfer).

8) Hang up to complete the blind transfer.

Relative to a true supervised transfer, the only things I believe to be 
missing are the inability to transfer the call while the desired 
recipient is on the line, and the ability to pick the call back up if 
the transfer fails - and these may be major problems for some 
applications. However, it comes close enough for many purposes.

For reference, I'm using a slightly modified version of the stdexten 
macro in the dialplan (no t or T) and either SIP INFO or INBAND on the 
phones.

Stephen R. Besch