asterisk.ru

Your other desk phones don't use hook flash, Asterisk doesn't listen for
hook flash messages on SIP channels, in fact the Siemens phone will send
a hook flash signal to Asterisk if you press the R key but Asterisk
ignores it.

Your desk phones use normal SIP methods to perform transfers (putting a
call on hold with a special Invite message, doing a transfer with a
Refer message...), this functionality is what has been added to the
Siemens phone. Whilst in a call you need to press the "ext call"
button, then you can announce the call to the person on the other end
and select the "transfer" option in the menu on the phone. If you have
the "transfer on hangup" option set to yes then you can just hangup and
the call will transfer, this method can also be used for a blind
transfer, just hangup while the 2nd call is ringing.

As for Asterisk config, if transfers are already working on other SIP
phones you have (using proper SIP transfers, not the ## code) then there
should be no extra config required. That was certainly the case for me
in our office and I've been using this firmware for a couple of months
in BETA before it was released.