Extracting only black color

I scanned an image and would like to use only the dark lines as a faded out background image. How do I extract only the black lines of the image? Or in other words how do I make the .jpg only show black and white colors and then be savable. The image is essentially a complex stick figure. The only problem is the background is a reddish color. Thanks.

If it is a photograph you can use the new tutorial I just posted.

http://forum.teamphotoshop.com/showthread.php?t=26149