Typically you will have a permanent phone extension associated with your extension number. That phone extension can be used to make and answer your calls regardless of whether you have one-X Portal running or not. Hot desking allows you to assume control of another phone extension so that it uses your extension number and phone system settings.
Normally logging in at another extension requires you to dial a special number including your login code that is different for the password you use for IP Office applications. However, you can use the one-X Portal login menu to both login to one-X Portal and to specify the phone to which you want to be logged on.
When you use this method to log in to both one-X Portal and a phone, when you log out of one-X Portal you are also logged off the phone. Your extension number is returned back to your normal phone extension if you have one and it is not in use by another hot desking user. If you don't have a normal extension or it is not available, you are treated as being logged off from the phone system and your calls will go to voicemail if available or receive busy.