The Push-To-Talk (PTT) license activates the PTT application in the handset and the use of the yellow button for PTT calls.
PTT is an automatic predefined conference call to a set of handsets and multiple conference groups can be configured. You can pre-define up to 5 different conference groups. When this group is activated e.g. via the yellow button, selection in a list, all members of that group automatically enters the conference call in loud speaking mode and with muted microphone. Any member of the group can then talk by pressing the PTT button.
Note that PTT and Function key functionality cannot simultaneous be active on the yellow button. Configuration is done in the Smart Manager.
When the PTT functionality is used, the Function key functionality it disables and vise versa. (This only applicable to the yellow button and not the red button).