Dell MH3021P User Manual page 11

6. Operation behavior on Button and LED
When powered up, top center LED
will light up in white.
During call:
Top center LED will change to green.
Incoming call:
During incoming call, call pickup LED
will blink in green, Call reject LED will
blink in red.
Microphone muted
When microphone is muted, all LEDs
will light up in red and stay red until
microphone is unmuted.
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