Guess I should have known better than to post !
Having just downloaded the "Sound of Silence" brochure from the Seinheiser website, let me reword my statement ....
"As far as I am concerned, a headset not requiring power is a PNR headset ... Passive Noise Reducton."
All the headsets in the Seinheiser brochure had a power draw requirement. The ones that did not use batteries, required the aircraft to provide the power.
Happy now Dream Land ?
