Interface design paradigm

This is the American Motors Corp. 1970 factory AM radio in its natural habitat. Nice looking radio and all that. Not only is it a "shaft-type" radio, non-DIN, but it's very shallow; even cutting the center dash piece all to hell won't fit a modern stereo.

Look carefully at this thing, interface-wise. There's not much to it, but it gets the job done quite nicely.

Knobs on shafts that rotate. Simple! Fits the human hand and wrist just great. Very intuitive -- infants figure them out (though infants usually pull the knobs off and put them in their mouth).

That knob on the left -- closest to the driver -- makes loud or quiet; that's all that it does. (The one function overload is volume-lowest clicks it off, reasonably intuitive, or not much to memorize.) Behind it is the tone control, on the same shaft, little used; you must poke around to find it, otherwise its existence doesn't interfere.

On the right is the tuner knob with a linear scale. Even if you have never used one a twist of the knob makes the pointer on the center scale move. Reasonably intuitive at that point. If the radio is on, and there are stations, turning this knob far enough makes a sound. Feedback.

(The above controls don't require any visual feedback, except for detailed selection of station. Recall that we operate this thing in traffic, in a car hurtling down a freeway (some 2 megajoules of stored energy at 60mph); not sitting at a desk with a dextrous pointing device. Please don't kill me while you play with your functionless eyecandy!)

The worst feature of these radios is the row of indistinguishable, identical, symetrically arranged station-memory pushbuttons. You have to consciously choose one by eye, unlike the other controls, visceral in nature. There's simple manufacturing convenience reasoning here, and it's more or less tolerable since there's so few of them anyways. The overload here is that you pull the button out to set it; not intuitive or obvious, but easy once learned -- and if you never do, you can always simply twist the knob. Redundancy is good. They make a substantial chunk when pressed; feedback is a side effect since it takes a bit of force to push them.

While the display on this particular model is hardly impressive (this was an economy car, $2500 new in 1970!), since it's physical, contrast is superb, it's readable in dark (backlit) or daylight, though it has a bit of parallax the resolution and accuracy suck anyways (linearity is about 10% full scale).

For a crappy device, it has a lot of good design, if a bit dull. (Actually, like "hub caps" on cars, the once-mundane is becoming rarer and interestinger (sic) as time passes...) Since my goal was twofold (good operational design, good aesthetic match for the car) a hacked AM radio seemed a good way to go.

Lesson #1: automobiles are prosthetic devices, not brain extentions. It extends the functionality of your body, and it works best when this is kept in mind.



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