Avaya phones have a series of letters that appear in the top of the display that are used to indicate the status of various features. After the initial training when a new phone system is installed, their meanings are usually forgotten so here is a refresher.
B = Barred
A B is shown on your phone's display when the system administrator has set you to outgoing call barred status. You will only be able to make internal calls while this is applied.
D = Diverting (Forwarding) Calls
A D is shown on your phone's display when you have forward unconditional enabled.
G = Group Member (In Group)
A G is shown on your phone's display when have been configured as a member of a hunt group and your membership is enabled. While this is the case, you may receive calls targeted to the hunt group. This is probably the most common one as virtually all phones will be part of a paging group or a pickup group.
N = No Calls (Do Not Disturb)
An N is shown on your phone's display when you have do not disturb enabled.
O = Out of Service
An O is shown on your phone's display when any of the groups of which you are enabled as a member is set to night service mode. In that mode calls to that group are diverted to its fallback if set or otherwise to voicemail if available.
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 on a phone's 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.