Anyone familar with tachometers in general?

There's a lot of scooter tach's out there which hook up to the CDI system one way or another, but they all have one very unfortunate requirement in common: They require a 12v power source.

Does anyone know if running the tach without the 12v power source will make it not work? Or is it simply to power the little internal lights in these things?


Thanks,

Kevin B.

Here's an example of what I was thinking of using:

VESPA LAMBRETTA TACHOMETER 12000 rpm - 2 STROKE : eBay Motors (item 370372504042 end time May-05-10 10:31:55 PDT)

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