From all appearances I would say this is a hand drawn, nicely done, diagram showing how to wire an Alpine electronic tach into a car that originally did not have an electronic tach. If this was included in some Alpine stuff, it seems reasonable that the author intended it to show how to install an Alpine electronic tach into an earlier Alpine that originally had a mechanical one. I note it does show the tach should get powered by +12 V, (if Neg earth car) or by ground (if Pos earth car) and shows the Case should be connected to the opposite (earth on neg earth car or -12V on a Pos earth car). This implies that the instructions are for a SV tach (Neg earth version, model 2411/01), and seems unaware of the fact that there are earlier versions of the tach designed for Pos earth cars , or that fact that either polarity tach can be converted to the other polarity internally. I would not recommend wiring a Neg earth tach, like this drawing suggests, into a Pos earth car by simply applying a ground connection to the power terminal and -12 V to the case. Too much risk of a short with the whole metal case "live" at -12 V relative to all the earth (Gnd) points around it. Not to mention the difficulty of installing the tach lamp which would cause a short unless you reversed its wiring as well.
The drawing does seem (dotted lines just below the case) to show how to interrupt the power feed to the coil and route it thru the sense loop on the rear, but I cannot tell if the instructions are clear that the steel U-clip is needed to make the loop effectively couple the ignition pulse to the tach electronics.
Tom
