Aska

Call Transfer in Asterisk dialplan

In this post, we are going to show you how to perform a call transfer through the Asterisk dial plan application.

What is a call transfer

Transferring a call means that one side of the conversation (A) tells Asterisk to connect the other side (B) to the third destination in the system (C). Asterisk supports two types of call transfer: blind and attended.

How to enable transfers in Asterisk

In features.conf, you must configure the blindxfer and/or the atxfer options in the featuremap section.

[featuremap]
blindxfer = #1 
atxfer = *2 

What do the blindxfer and atxfer parameters stand for.

• blindxfer = This allows you to perform a blind transfer
• atxfer = This allows you to perform a attended transfer

Blind Call Transfer in Asterisk

Blind transfer means that its initiator (A) forwards the other party of the conversation (B) to a third party's phone (C). When A presses the transfer button, he loses the connection with B and C. Instead, a separate connection is established between them.

# to do a blind transfer press #1 on a active call
exten = 100,1,Dial(PJSIP/BOB,30,T)

Asterisk should be restarted for changes to take effect.

Attended Call Transfer in Asterisk

Before transferring a call, party A first connects to party C, makes sure they are ready to receive the call, and then transfers party B to C. Thus, the initiator of the transfer controls the process until it is completed. It is especially useful when the transfer initiator wants to make sure that the receiving party is ready to accept the call in advance.

# to do a attended transfer press *2 on a active call
exten = 100,1,Dial(PJSIP/BOB,30,T)

Asterisk should be restarted for changes to take effect.

Asterisk has a few extra features that can come in handy when you are using the transfer function. You can add these features to your features.conf.

transferdigittimeout = 1; Number of seconds to wait between digits when transferring a call
xfersound = beep ; to indicate an attended transfer is complete
xferfailsound = beeperr ; to indicate a failed transfer
transferdialattempts = 3 ; Number of times that a transferer may attempt to dial an extension before
being kicked back to the original call.
transferretrysound = "beep" ; Sound to play when a transferer fails to dial a valid extension.
transferinvalidsound = "beeperr" ; Sound to play when a transferer fails to dial a valid extension and is out of retries.