1.) When dialling an internal telephone number (extension), you only need to enter the extension number.
2.) When dialling an external telephone number, you must first dial “0” before dialling the external telephone number.
3.) To complete dialling, press the “Call key” in either case 
or use the “Dial” softkey.
4.) To end the call, press the “Call key" again 
or press the “End” softkey to end the call.
