speedometer/tachometer signal
 

I'm not looking forward to setting up a scope and an inverter in such a small car, but has anyone looked at the signal leading to the fuel pump relay/cruise control on a 107, specifically an 86 560? I'm guessing (this is not explained in detail in the CD manual)g that there is a Hall effect sensor on the tranny output, then it's cleaned up/amplified by circuitry on the back of the speedo, then a (possibly 5-12V pulse) is sent to the fuel pump/computer/cruise.

What does it look like? About how many pulses per MPH is it?