I went through this simple project. I understood most part of it except the line that says "This frequency can be trimmed to exactly 1 kHz with the help of trimmer capacitor VC1". i know that trimmer capacitors are variable capacitors. but how does a capacitor modify the output frequency?

http://www.google.co.in/url?sa=t&so...sg=AFQjCNGf-qKsSwTnynNNbwGBBo0YCed6FA&cad=rja

 

Hello,

The capacitor makes a load for the crystal and shifts its frequency.
Take a look at the attached PDF for more info.

Bertus