The Feature Status Lamp is not used, as far as I know, on the CS1000, except when doing a firmware update. There is no way to control the light with the CS1000 / Copilot, as far as I am aware.
On the Nortel CS2000 (now owned by Genband and called Genband C20), the blue feature status lamp on the 1100 series phones illuminates when the phone is on an active call.
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