You can configure the Busy Lamp Field functionality for additional lines on a Cisco SPA series phone, which would allow phone user see if these lines are currently being used by other users. Please follow the instructions below:

  1. Obtain the IP address of your phone
    • Press the Setup button (this button looks like a piece of paper with a folded corner).
    • In the Setup menu, navigate to Status. Scroll to Network Status and press select to view the IP address of the phone.
  2. On your computer, open a Web browser and type the phone's IP address in the address bar. You will see the web interface for configuring your phone.
  3. Click on Admin Login > Advanced in the upper right corner.
  4. Click on Attendant Keys tab > change Server Type to Asterisk > change Attendant Console Call Pickup Code to *98#Attendant Keys
  5. Click on Phone tab, scroll down to Line Key # section (where # is the number of the key you are to configure).
  6. From the drop-down Extension menu select Disabled and then enter the following line into Extended Functionfield:

    fnc=blf+cp;sub=xxxx@hpbx0xx.serverdata.net;nme=xxxx

    where blf stands for Busy Lamp Field, cp allows you to pick up the calls on this line, hpbx0xx.serverdata.net is your Hosted PBX server, and xxxx should be replaced with the user's extension.
    BLF

  7. Click Submit All Changes. After the phone reboots, the key will display the following color LEDs for the monitored user:
    • Green: Available
    • Red: Busy
    • Red Fast Blink: Ringing