When your own extension name is shown on the second line of the display, for example when the phone is idle, the name may be followed by a series of letters. These letters are used to indicate your current status.

B = Barred
A B is shown on your phone's display when the system administrator has prohibited you from making outgoing calls. You will only be able to make internal calls when your status is set to Barred.
D = Diverting (Forwarding) Calls
A D is shown after your extension name on the phone's idle display when you have 'forward unconditional' enabled.
G = Group Member (In Group)
A G is shown after your extension name on the phone's idle display when you have been configured as a member of a hunt group and your membership is enabled. With this status active, you may receive calls targeted to the hunt group.
N = No Calls (Do Not Disturb)
An N is shown after your extension name on the phone's idle display when you have 'do not disturb' enabled.
O = Out of Service
When a group is set to night service mode, all members of that group retain an 'out of service' status indicated by an O on the idle display.  Calls are diverted to the group's fallback, if set. Otherwise, the calls are sent to voicemail (if available).
R = Resilience
An R is shown after your extension name on the phone's idle display to indicate that your phone is working in resilience mode. This is used when there may have been a problem with the telephone system to which your phone was registered and another system is currently providing support for your phone. In this mode, some features may not be available and calls may be routed differently.
S = System Alarm
If you are configured as a system administrator, an S in the phone's display indicates a system alarm.
T = Twinned
A T is shown after your extension name on the phone's idle display if it is internally twinned with your phone. Calls to you will alert on both phones and can be answered by you at either phone.
! = Cannot retrieve user settings
An ! is shown if the telephone system at which you have logged in could not contact the telephone system that stores your user settings. If this happens it limits the telephone functions, including making and receiving calls, that you can use. Contact your system administrator.