Wendell said: "The system uses two pickups and compares the signals."

The long series of cruise controls that I have installed on many different
vehicles used only the coil sensor unless I was installing on an automatic.
 The documentation uses the term "electronic clutch switch" and there is no
physical clutch switch.  Depressing the clutch on a car with one of these
systems engaged causes the engine to increase speed momentarily and then
the cruise shuts down.  Since there aren't two signals to compare, I
conclude that the unit watches for an increase in engine speed that is not
consistent with normal vehicle acceleration.

Mike

'84 GL  '58 Isetta