[function_seven]

This is a two part system. There's the relay under the hood, and a keypad plugged into the cigarette lighter port. When you put the correct code in, the device will induce the voltage fluctuations that tell the under-hood relay to close.

I think the whole "flip on wipers, flash high-beams twice, turn on map light" thing is a fallback for when you don't have the keypad or don't want it to always be plugged in. If the voltage variances for those actions changes, I suppose you can retrain it with the keypad plugged in.

And the point of that analog signalling is to make installation easy. You just plug the keypad into the lighter port. It handles the rest.

[hunson_abadeer]

Right, but that voltage modulation scheme can be distorted by the changing electrical characteristics of your car. Again, imagine a diesel heater kicking in, or windshield wipers, or some other variable load (phone charging)... you can have a clever fault-tolerant modulation scheme, but probably not if you want to also support "blink headlights" as a backup input method?

Beyond that, I don't see the "simplicity" argument for analog. You're already messing with the vehicle's wiring. CAN bus is easily accessible from the passenger compartment. Or, running an extra data wire takes 10 minutes. Short-range RF can be easily secured in this application too.

Plus, on many newer cars, USB charging ports are displacing 12 V outlets, so it's not even all that future-proof.

It's not that I'm desperate to dislike this design, but I'm struggling to see the qualitative improvement over a billion aftermarket designs that most people just kinda don't use...