Avaya one-X Deskphone Value Edition 1608-I - Manual (Page 39)

you are away from your desk. The cell phone number is programmed by your system
administrator.
If you use a Feature Access Code to enable EC500, the forwarding icon does not appear in
the phone display.
1. Press the EC500 feature button to turn the feature on.
The green LED next to the feature button turns on.
2. To turn the feature off, press the EC500 feature button.
The green LED next to the feature button turns off.
Activating Extension to Cellular (EC500)
Avaya 1608/1608-I IP Deskphone User Guide February 2010 39