IP Office Basic Edition - Analog Phone User Guide: Introduction
When on a call, you may want to put that call on hold and reconnect to system dial tone so that you can dial the code to activate a special feature or make another call, for example to transfer or conference a call. This can be done by sending a hook flash signal to the telephone system.
The method by which this is done varies depending on the individual model of analog phone that you are using:
•Some analog phones will have a recall button (not to be confused with redial). The button may be marked R, Recall, Flash or Hold.
•On phones without a dedicated button, you can send a flash hook signal by briefly tapping the handset hook switch.