Cruise Control Signal Alteration

[Riles]

Hey guys, I'm trying to work on something that can make the cruise control think the car is moving slower or faster than it really is.

Here is my question- does the cruise control run off of pulses or voltage, or something else entirely? I'm looking at the wiring diagram in my chilton's manual, and I see that the cruise control is connected to the pcm via the same wire that the speedo is.

Any advice on what would do the trick? Thanks!