EPM: Improve Transfer Handling on Yealink and Grandstream phones

PLEASE CLOSE THIS ISSUE, I POSTED AGAIN ON THE RIGHT SECTION, THIS IS ABOUT EPM (Commercial)

The transfer key on Grandstream phones default to blind transfer.

I believe the best default for EPM to use on Grandstream phones is Auto Attended Transfer where the user can choose between blind and attended transfer every time and the user can do this using the transfer button and without having to remember key sequences to dial.

Another possibility is to enable transfer on Conference hangup, although I haven't tested this functionality. But then a user could achieve an attended transfer by joining the party it wants to transfer to to a conference and then hanging up.

Options are:
P1376=1 (to enable auto attended transfer)
P2304=1 (to enable transfer on hangup)

For Yealink the best setting is:
transfer.dsskey_deal_type = 1