The USB Telephone adapter has three LEDs that indicate the current status of the unit.
The Power LED is lit if the USB Telephone Adapter is correctly connected to your computer and your computer is on.
The Telephone LED is lit if you have your USB Telephone Adapter connected to your computer, your telephone, and a wall jack. This LED is not lit when you are on a Skype call.
The Skype LED is lit while you are making a Skype call, or if you only have your USB Telephone Adapter connected to your computer and your telephone.
The status of the USB Telephone Adapter software that runs on your computer, USRAgent, is displayed in the Windows system tray.
When the system tray icon is grey, the USB Telephone Adapter is connected but inactive.
When the system tray icon is green, the USB Telephone Adapter is connected and a Skype call is active.
When the system tray icon is crossed out, USRAgent has detected a problem with the telephone adapter.
If you want to verify that your USB Telephone Adapter, telephone, and Skype are all working and configured correctly, you use the Skype Test Call service.