Comdial DSU II SCS84125J Station User's Manual page 95

Switch between your telephone and the IST device by pressing the
DATA button that the installer has programmed on your telephone.
The light associated with the DATA button provides status indications
for your reference.
DATA Light
OFF
On Green
On Red
Flashing Red
August, 03
DSUII LCD Speakrphone User's Guide
Telephone Status
Your telephone is selected for operation
Your IST device is selected but is idle
Your IST device is selected and is busy
Your IST device is ringing
IMIST Module
Comdial 85