I just installed classic instrument speedo in the car with the SN77. I brought 2 wires from the transmission, where the pulse generator on the tranny is. One is a purple wire and one is a green wire. My question is which one is the ground, or does it matter? As on the SN77 box it has sensor ground. Thank you for your help.

 

Its and tiny pulsed DC generator I dont think polarity would not matter as its and isolated circuit. However I would check with the cluster manufacturer myself first. Just in case.

 

I was under the impression that it put out an AC signal.

 

I havent measured one but they do have a single armature so it would seem impossibe to get a wave form from that So I would say pulse generator