You can use the Apps app to access special services on the phone.
You can use the Application button to start applications such as Push to Talk or other services on your phone. The Application button is located on the left side of the phone.
Depending on how your administrator sets up the button, you may be able to use it from the main screen only, or you may use it from any menu or service, or even when the phone is locked.
The button can also be configured to start an application immediately after you press it or only after you hold it for several seconds.
For more information, contact your administrator.