I have a Dixson Instruments model 540G1-47302 tachometer that appears identical in size (3-3/8") to the standard HMMWV tach and is marked for use on 24 volt systems. What concerns me is the label is marked "4 cyl". The terminal strip on the back is labeled + and - and then the center 2 teminals are marked "sig". I'm trying to find out if this could be used in a HMMWV. Dixson Division of Ametek has no information on it and I'm wondering if anyone on the list has ever played with one of these?