Analog SFF, December 2009 - By Dell Magazine Authors Page 0,1

to the current value of that variable on a printed scale. The on-off switch could be a toggle or slide, or a push-button, or a rotary switch that clicked off counterclockwise and on clockwise. The closest such a device was likely to get to combining functions in one control was fairly common but simple: a rotary or push-button on-off switch might be combined with the volume control in a single knob. That made straightforward sense since “off” can be thought of as the ultimate stage of “down” and “on” as the first step “up.” With that semi-exception, each control did one and only one operation, and there was no other way to do that.

Things hadn't changed all that drastically by 1948, which is probably why Campbell didn't mention the additional difficulty I'm pointing out today. But they had changed significantly. Electronic devices had become more versatile and controls had begun “multitasking” to accommodate that fact. A radio might now cover not just a single AM band, but several of widely different frequency ranges (broadcast and shortwave), plus another using frequency modulation (FM). It might also have an input allowing a phonograph record to be played through its audio stages. So it would need at least one selector switch, most likely a rotary switch with a knob pointing to AM, FM, SW1, SW2, SW3, or PHONO. The tuning dial would still have one pointer but several parallel scales, each labeled to correspond to one of the selector positions, so it wouldn't be too hard to figure out which of the several simultaneous indications was relevant. The volume control would still be a volume control, regardless of the selector position. There might also be a tone control, or perhaps two (treble and bass). If the radio was powered up and working, the function of each control could quickly be determined by experiment, even if the experimenter couldn't read the markings. If it was not powered, there'd be more guesswork involved.

But now, fast-forward to 2009 and try to imagine one of our radios, computers, cellphones, or iPods falling into the hands of Campbell's 1920ish engineers. First off, a radio that's just a radio is something of a rarity these days. The one in my car is also a CD player and an audiocassette player, and it only has two knobs: one labeled VOLUME and one labeled MODE. Everything else is push buttons and a couple of rocker switches, and most of the indicators are digital liquid-crystal displays that aren't even visible when the thing is turned off. When it's on, what the displays show is completely different depending on which modes of operation are chosen with the push buttons—and even what the push buttons choose is different depending on what other choices have already been made.

Given suitable power to operate the thing, a good engineer from either 1920 or 1948 could eventually figure out how to use it, but I think he'd go through a good deal of head-scratching and hair-pulling first. Its whole psychological framework for relating controls to functions is radically different from what he was used to. He'd probably start with the VOLUME knob, the only thing there that looked and sounded like anything familiar. He would be reassured to confirm that it does indeed control volume, and pushing it turns the unit on or off. But eventually he'd discover that it can also be turned on—but not off, and only sometimes on—by any of the pushbuttons labeled AM, FM, CD, or TAPE. (If there's a CD or tape in the relevant slot, pressing the corresponding button turns the system on and starts playing the indicated object wherever it was last stopped. Pressing CD while playing a tape immediately switches to playing the loaded CD, if there is one. Pressing CD when the unit is off and no CD is loaded does nothing.)

Not knowing about CDs or tapes, our intrepid engineer (at least the one from 1948) would probably start by trying the FM or AM button, since those are at least recognizable terms. He still wouldn't see a recognizable tuning dial; just, say, “FM1” and a single number like “96.3.” The 1948 engineer might say, “Aha! That sounds like an FM frequency,” and rightly conclude that he was on the right track; for the fellow from 1920, it wouldn't ring any bells (or bring in any stations). Either of them might discover by experiment that the rocker switch labeled TRACK/TUNE would make the displayed number go higher or lower