Tap to open the main menu. From the main menu, go to Settings > Advanced Settings to see the following options:
|Prevent Auto-lock||This setting prevents locking the screen while you are on a call using the app.|
|External Dial Prefix||Enter the number required by your iPBX to dial out to an external number.|
|Emergency calls via cellular||Enable to dial the emergency number 911 through your standard cellular network.|
Note: Synchronization may impact performance if your contact directory is large.