Tach swap from another 4 cylinder car reed switch?

[getnpsi]

I need a cliff notes in electronics class Im afraid. In the process of adding a cluster from an obd2 hyndai to the festiva. On the back of the new tach cluster one of the wires is positive, there a tach negative and another one marked reed switch. Does the festiva use this exact setup as well or do i just use tach positive and negative and it will work? I dont want to fry anything holding alligator clips poking along and finding out the hard way frying a ecu or working cluster.

I dont have a festiva tach cluster to compare the boards and wire leads or id simply put it in. Figured id play with something i had on hand

[zoom zoom]

tach signal is a pulsing ground from the disty I think. If your using a VSS in combination with that cluster the wires should probably all come off of that? The disty puts out two tach signals, one wire goes to the ecu the other has the metal wrap referred to as "shielding" (like the o2 sensor wire) that goes to the cluster. Not really sure what a reed switch would be?!

[getnpsi]

Reed switches are used with tachs for electric motors a lot. I am not going to use a vss if i can help it. I was hoping i could just use the tach like an aftermarket one or how the festy/aspire is done, with something coming off the disty. I got excited the speedo is a 140mph and the revolutions were the same. Was hoping to make this a relatively painless epoxy'ed deal.I know some people have miata gauges, and those cars have more advanced electronics...but they may have used the miata wiring harness and was plug and play?