I noticed that the headphone that is included with the N900 has 4 contacts (the output jack has also one Video channel):

Do I need an adapter like this one:
http://www.amazon.de/Headset-Audio-A...=27O4BBG2ZAFR6

or can I simply plugin usual 3 contact 3.5mm headphone jacks?

(I want to use my usual headphone...)