The Model 13 is a one of a kind clock, partially a design study in the use of an analog D'Arsonval meter movement for information display. The Model 13's cabinet is a General Electric portable laboratory AC voltmeter, available from the late 1930's through the mid-1950's. The original meter movement was retained, and the meter card recalibrated with scales necessary to display time and date. The original voltmeter probably dates from the late 1940's or early 1950's. The escutcheon is tin-plated brass, etched and enamel-filled; the four switches are hand made for a precise tactile feel.
Internally the clock is built around a state-of-the-art microcontroller, with a lifetime clock/calendar integrated circuit. The entire clock is powered by five AA cells. A fairly complex set of software routines are necessary to accurately present time on the primitive and decidedly nonlinear meter movement.
The clock is operated entirely by the four front panel switches; the time or date is displayed by pressing the TIME or DATE switches; the current time or date is displayed for 8 seconds, then the clock shuts itself off to conserve power. Setting the clock is admittedly obscure; an instruction card is mounted within the cover. The difficulty is due to the limited conceptual bandwidth of a meter pointer and scale.
As far as is known, no commercial clock ever used this type of display, though it is compact and efficient. The D'Arsonval meter movement, and a handful of variants, was very nearly the only practical display device for numeric information for nearly a century, and has been replaced only in the last 20 years with solid-state displays. Until 1975, it is safe to say that every technical person could read one; now nearly no one can. A meter scale shares the same principles with the slide rule.
Mixed media (bakelite, glass, brass, electronic
components), 2.75"h x 4.75"w x 6.75"d, approx. 3