Shared lines are an optional feature configured on the server and may not be supported on your particular system. Contact your system administrator to find out.
A shared line is indicated by a different line icon. In the figure, the first line is private and the second line is shared. If two phones share a line, an incoming call to that number will cause both phones to ring. The call can be answered on either phone but not both.
If a shared line is in use on one of the phones, it may be unavailable on the other one. The shared line icon changes to a moving icon and the line LED turns red when the line is in use remotely.
Calls on shared lines can be transferred, put on hold, or added to a conference.