Log into Phone and Navigate to Admin - Advanced
Click on Admin Login and then on Advanced.
Navigate to Phone Tab
Click on Phone tab to locate the correct fields.
Configure BLF on Desired Line Keys
The Line Keys are numbered down the right side, and then down the left side if you phone supports them. Leave Line Key 1 alone to ensure it acts as your user line properly. In this case, we assigned Line Key 2 to monitor Sean and Line Key 3 to monitor Jim.
Change Extension dropdown to Disabled.
Change Share Call Appearance to Shared.
Change the Short Name to reflect the label you desire on the phone display
In Extended Function, paste this code in, changing the 0001*1001 to your full extension number: fnc=blf+cp+sd;sub=0001*1001@$PROXY;ext=0001*1001@$PROXY
The breakdown of that line: fnc=function; blf = busy lamp field; cp = call pickup (reserved for future use); sd = speed dial; $PROXY is the placeholder for the SIP server.
Click Submit All Changes at the bottom. The phone will reboot and the Line Keys you programmed should then monitor the extensions.