Knock Sensor?

Can anyone tell me were I would find the knock sensor on a '91 Regal Limited with a 3.8? Are there two? What do they look like?

it is located on the front of the cylinder head.that would be where the belt is.here's a link of what it looks like.

http://catservices.wrencheadpro.com/smartpages/partinfo_resize/ACD/213-91.jpg
and i only know of 1 ,i don't believe there are 2.