Asterisk Transfer an active call to another extension

Question

Here I have a scenario:

H: means a Hotel frontdesk staff, the Hotel's number is 12345678

A: means a person outside the Hotel

B: means a customer inside the hotel of Room1000

A make a phone call to 12345678, and H pick up the phone call; then A tell H that he want to contact the customer inside Room100, after authentication, H TRANSFER THE PHONE CALL TO B AND HANGUP.

My question is, how to blind transfer the phone call to B. The channel is set up based on SIP protocol.

Edit

typing cmd $ asterisk -rx "features show"

Builtin Feature Default Current --------------- ------- -------

Pickup *8 *8
Blind Transfer # ##
Attended Transfer *2
One Touch Monitor *1
Disconnect Call * **
Park Call
One Touch MixMonitor

Dynamic Feature Default Current

--------------- ------- -------

apprecord no def *1

Feature Groups:

(none)

but when press ## in softphone it will lead to "Extension not found". Any idea?

Answer 1

By default it is *2+number+hangup phone.

You can see your code by dooing

asterisk -rx "features show"