I played around with it a little last night. It also works as a voltmeter and ammeter. The two leads with the battery charger clips work for voltage/amperage testing. I hooked the negative one of those to ground and the small wire with the alligator clip to the negative side of coil and was able to check my dwell. That didn't seem to work for the tach like I was expecting though. I still don't know what that other set of wires is for that has the bar attachment.

Aaron