Ode to a round knob

“O knob, thou whose perfect roundness doth . . .”

Nah. A poet I’m not. Still, I would if I could, because the round knob is a fast disappearing species, a trend well worthy of lament.

Round control knobs on an oscilloscope

Throughout the 20th century the round control knob was a mainstay of human interface design for electronic devices. With good reason: it was perfectly suited to humans’ major feature, the opposable thumb. You grasped the knob between that thumb and forefinger and you had superb fine control of the knob’s angular position. If the function called for finer control, you just used a fatter knob. At the machine end of this human/machine interface the knob could rotate a switch, a variable capacitor, or a potentiometer – there were many analog devices back then that lent themselves well to rotary control.

Today most of our input components have gone digital, and are either computer controlled or handled by pushbutton switches. This makes sense in some cases, but there are still many situations when a function is intrinsically analog (say, a volume control on a car radio) yet the designers are making the controls digital (say, by using a pair of + and – pushbuttons). This is pure evil from a human engineering perspective: the round knob is much more intuitive, convenient, and faster to boot. And it really was worthy of the name control: it gave the user a sense of controlling the instrument, instead of fighting it…

I’m sure the electronics driving the volume these days are fully digital, but even so a round knob with some D/A conversion is the correct choice. It must also be more expensive to make, because the radio makers – preferring low cost to user experience – increasingly shy away from it. 🙁

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