Hello,
I own a Kenwood TS-450S. They do not come with a keyer built in.
I personally use a Picokeyer:
http://www.eham.net/reviews/detail/3706The keyer will plug directly into your CW jack on the back of the rig. The keyer will act just like a straight key as far as the radio is concerned.
Good luck!
Joe N0NS