The Sun electronic tachs that were used in the 1950's and early 60's had a sending unit that looked like a big voltage regulator, with a brown Bakelite cover. I believe some of them were dealer-installed as an option on medium-duty trucks back then. They used a set of Mallory mercury batteries in an oddball voltage, and those batteries went obsolete many years ago. I've seen original-appearing systems that were actually rebuilt with modern electronics, but I don't recall what company was doing the conversion.
Jerry

Last edited by Hotrod Lincoln; 11/21/2009 4:28 PM.
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