HowTo: Configure DTMF based call transfer


This feature enables a user to do a blind or attended transfer from any device supporting DTMF. This is particularly useful to provide call transfer functionality on a mobile phone.

The call transfer works like this: While in conversation with another party, you dial '*'. Asterisk says "Transfer" then gives you a dial tone, while putting the other party on hold. You dial the transferee number and talk with the transferee to introduce the call, then you can hang up and the other party will be connected with the transferee. In case the transferee does not want to answer the call, he/she simply hangs up and you will be back to your original conversation. Press '*0' , to return yourself to the original caller.


  • Asterisk-1.2 module v2.22+
  • CallDevice action v1.23+
  • Goto.Interface v1.32+
  • Reserved Global Parameter AsteriskDialOption


Step 1: Enable the feature for all the call to an internal extension

DONE Navigate to: Communication Flow Studio > Global Parameters > Reserved

Add the options 't' and 'T' to the global parameter AsteriskDialOption. For example, set AsteriskDialOption to 'otT'.

Step 2: Enable the feature for all the external call going through a specific interface

DONE Navigate to:  Communication Routing > Define Routes

Enable the 'DTMF call control' option of the Goto.Interface action for each trunk

Step 3: Configure the Restriction Group used during call transfer

DONE Navigate to: Communication Flow Studio > Global Parameter > Context

  • Parameter name: TRANSFER_CONTEXT
  • Friendly name: call transfer restriction group
  • value: NoRestrict
  • Owner type: Admin var
  • Description: context used for DTMF based call transfer

Copyright © Escaux SA