Quick question for Sennheiser MKE 300 owners -

["ndbdxr" ndbdxr]

Dear Folks,

I recently acquired a second-hand MKE 300 microphone, I'm wondering why the red 
LED (to the right of the On/Off switch) does not stay illuminated when I turn 
it on? 
The mic seems to work OK. But when switching it on, the LED only lights up for 
a second, and that's it. Is this by design, or is mine faulty?
...I've tried 3 different brands of brand-new / fresh batteries.

Thanks in advance & best regards,
-Al