Certain high-end Datsun models of the Late Malaise Era came with a seriously science-fictiony feature: the car talked to you! That's no big deal nowadays- $1.29 worth of silicon- but back then it took hardware.
I'd always assumed that Nissan just liked cool gadgetry so much that they'd gone ahead and used $1,278 worth of first-gen Mesoproterozoic Era solid-state digital audio circuitry, no doubt with a shoebox-sized brain packed with 128 whoppin' kilobytes of data.
But no! They created a miniaturized, shock-resistant phonograph, using a 3" white plastic record cut with six parallel grooves (one for each voice message, including "Left door is open," "Right door is open," "Parking brake is on," "Fuel level is low," "Keys in the ignition," and "Lights are on."), and a super-precise stylus that drops in just the right groove when triggered by the device's control circuitry. We're talking about the very pinnacle of analog automotive devices here, and I never knew it existed until a recent junkyard trip. That's when I found an intriguing box labeled "Audible Warning - Don't Drop" under the dash of a 1982 Datsun 810 Maxima.
Naturally, I had visions of rigging up this fine retro device in my Civic (or maybe hardwired into the Junkyard Boogaloo Boombox), but the vast number of wires coming out of the thing meant that I couldn't get anywhere without a wiring diagram. $10 later, I'd purchased a factory shop manual on eBay and got down to business.
Sadly, the friendly Japanese Audible Warning Box seems to be garbooned; I've wired it up in a manner that should convince it that it's still in a Maxima, but the stylus arm never moves when I trigger the "door switch" or "fuel level sensor" conditions. All I get is a forlornly spinning phonograph record and some little clicks from the mechanism. The only thing I'm not certain about is the mysterious item labeled simply "Audio" on the schematic; I'm guessing it's a circuit in the stereo that cuts the music during announcements. I've got these things on my junkyard shopping list, so I'll make one work yet!