February 1973 Popular Electronics
Table of Contents
Wax nostalgic about and learn from the history of early electronics. See articles
published October 1954 - April 1985. All copyrights are hereby acknowledged.
Try as I did, I could
not find any instance of the Ness Clocks all-digital liquid crystal display (LCD) desk top which
appeared in this 1973 Popular Electronics article. There must not have
been many produced. LCDs had only been commercially available for a year or so when
this went on sale. Of the relatively few digital display clocks and watches available
in the 1970s, the vast majority used light-emitting diodes (LEDs), and most sold
for north of $100 (~$600
in today's money). Portable devices with digital displays really began to flourish
with the advent of both CMOS circuitry
and LCD displays; i.e., low current devices that extended battery life. Wrist watches,
which could only accommodate very small batteries with limited energy storage capacity,
were amongst the greatest beneficiary of the technology. It was a big deal as evidenced
by this article and many others like it in the era.
Tiny Quartz Crystals and IC's Are Revolutionizing
the World of Timekeeping
Electronics is currently creating a major revolution in the staid old world of
timekeeping. Wristwatches designed to gain or lose no more than a minute a year
are already beginning to take a prominent place in the market. Some are selling
for less than $125, and the price is realistically expected to drop even lower in
the near future. The new electronic timepieces require little or no cleaning or
adjustment. Nor is it necessary for the wearer to wind his watch daily; the electronic
watches operate a year or more on a single miniature battery.
The new generation of electronic time-pieces is the offspring of a logical mating
of the quartz crystal with newly developed solid-state devices - emphasis in the
latter area being on COS/MOS (complementary-symmetry/metal oxide semiconductor)
integrated circuits. Steering away from traditional mainsprings, gears, and cogs,
the new timepieces keep time via a tiny bar of quartz crystal and an integrated
circuit which provide an accuracy heretofore unattainable in even the most expensive
mechanical movement in consumer watches.
Fig. 1 - Simplified block diagram of typical electronic watch
with conventional hands. Circuit can be used to drive stepping motor, synchronous
motor, or balance wheel. In any case, the motor or wheel drives the hands as found
on the typical watch face.
All-Electronic Desk Clock
Ness Clocks, Ltd., of Palo Alto, California, is producing an
all-electronic desk clock built around digital IC technology and liquid crystal
readouts. The new $150 timepiece derives its time from a special LSI timing chip.
The output of this chip drives a newly developed liquid-crystal readout system.
The liquid crystal display is guaranteed for two years. Should it fail, the display
can be unplugged from the clock and replaced with a working system in about the
time it would take to change a light bulb. The readout is in minutes and hours,
with an AM/PM indicator which pulses once each second. Clock accuracy is said to
be within several seconds per month.
The quartz crystal is the key to the precision timing in the electronic watch.
But new developments in solid-state technology are what must be credited with bringing
the electronic watch onto the consumer market according to Harry Weisberg of RCA's
Solid State Division, pioneer of the new COS/MOS technology in IC's.
Mr. Weisberg explained: "The principle of using quartz as a time base is not
new. It has long been employed in laboratories, by the U.S. Naval Observatory, and
in other applications requiring precision timing. However, the introduction of quartz
into consumer watches had to await a technology such as COS/MOS which could reduce
the cost, size, and power requirements of the electronics associated with the quartz
Indeed, COS/MOS technology has blossomed, and with it, the electronic wrist-watch.
More than a dozen U.S., Swiss, and Japanese firms are either developing or marketing
electronic timepieces. Among them are the most prominent names in the industry;
Hamilton, General Time, Patek Philippe, Omega, Timex, Longines, Bulova, and Seiko,
to name just a few. Most of these employ COS/MOS-type circuits supplied by such
top names in the field as RCA, and Motorola.
All of the current batch of electronic wristwatches operate in basically the
same manner. When power is applied to the quartz crystal, the crystal's piezoelectric
property generates a high-frequency signal, commonly in the 30,000-to-50,000-Hz
range. (The smaller the crystal, the higher the frequency.) The high-frequency signal
is then divided by an integrated circuit to yield a 1-Hz (1 pulse/sec) output signal
which is used to drive either conventional mechanical hands or is decoded to drive
The excellent stability of the quartz crystal - an attribute that has also made
the crystal the frequency controlling device for broadcasting radio signals for
decades - and its ability to produce the high-frequency signal account for the accuracy
of the electronic watch. In effect, the quartz crystal splits a second into 30,000
to 50,000 parts as compared to the 360 parts produced by the tuning fork used in
the most accurate conventional watches.
The greater the number of parts into which a second is split, the greater the
obtainable accuracy. However, the electronic watch's frequency is determined by
a cost/power tradeoff. A smaller high-frequency crystal is less expensive than a
larger crystal of lower frequency, but it requires more power.
The greater accuracy of the quartz crystal approach also results from the elimination
of the traditional mechanical parts whose precision is determined by the care exercised
in their manufacture but deteriorate in normal use through wear. The substitution
of solid-state parts for mechanical devices also means fewer malfunctions. And when
repair is required, the problem in an electronic watch can quickly be isolated to
one of a few components. It is not difficult to foresee the day when component repair
of electronic watches will be done away with altogether. Breakdowns will be so infrequent,
and the working portion of the watch so inexpensive, that when a malfunction does
occur, the entire timing unit will be discarded and replaced with a new one.
All-electronic Pulsar (Hamilton, HMW Industries) displays time
digitally with light emitting diodes which are activated when wearer presses button.
The COS/MOS circuit is an ideal teammate for the quartz crystal in an electronic
watch. The large-scale integrated circuit COS/MOS chip can contain 1500 or more
elements in a space the size of a match head and, therefore, fits in with the size
requirements of the wristwatch. It also generates practically no heat and is highly
immune to electrical noise. But perhaps the principal attribute of the COS/MOS IC
for timing applications is its incredibly low power requirement, measured in microwatts
(millionths of a watt), which is a tremendous advantage in situations where a small
battery must last a long time.
Analog & Digital Watches
The quartz crystal and IC keep the time. The manner in which the time is displayed
falls under two basic categories: analog which retains the traditional moving hands,
and all-electronic which displays electronically generated numbers.
In the analog watch, some mechanical features of conventional watches must be
retained to control and operate the moving hands. One version employs a stepper
motor (Fig. 1), another a tuning fork, and still another the traditional balance
wheel. These mechanical devices are driven by the output from the quartz crystal/IC
system to achieve electronic accuracy.
The major advantage of the analog electronic watch is its low cost. Hence, the
lowest cost electronic watches, expected to be priced at about $50 within a year
or two, will almost certainly use a moving-hands display. (An alternative analog
movement employs mechanical wheels that display the time in a digital manner.) Whether
it uses hands or the digital wheel, the analog watch still has moving parts that
are subject to wear and require periodic cleaning, oiling, and adjustment.
In contrast, the all-electronic watch contains no moving parts to wear out. The
output of the IC triggers a display that flashes the time in discrete numerals (Fig.
2) . Too, encapsulation of the electronic components eliminates the need for cleaning
Interior of Pulsar Wristwatch
Gray bar at top is quartz crystal, black square is IC, LED readout
The readout display for all-electronic watches is a principal area in which technology
is still undergoing development. One approach is to use light-emitting diodes (LED's).
But LED's are basically power hungry devices. Using them in a wristwatch with a
continuous-duty display cycle is impractical when the only powering source is a
small battery. In one LED-display watch on the market, for example, the wearer must
push a button to activate the display for a few seconds, after which the display
extinguishes. The LED's otherwise would drain the battery in short order.
Liquid crystals are the prime candidate for providing practical continuous-duty
readout systems in electronic watches. They require very little driving power, and
when teamed with micropower COS/MOS logic, can yield operating lives of a year or
more from a single battery. Another advantage of LC's is that they are activated
by ambient light. The brighter the light, the more visible and clearer the display.
But by the same token, LC readouts cannot be read in darkness since there is no
activating ambient light.
Regardless of the outcome of developments now under way to improve readouts,
costs for all-electronic watches are already beginning to come down. As the watches
gain in popularity and technical advances are made, major price reductions are envisioned.
They require one BCD (binary coded digital) seven-segment decoder for each display
Although the most dramatic and visible impact of electronic timekeeping has been
in wristwatches, the technology is also being put to work in other areas. Desk and
wall clocks are also employing the electronic approach. So are industrial timing
systems and marine chronometers.
Fig. 2 - Block diagram of multiplexed system for producing digital
display of time. Non-multiplexed systems can also be used.
Motorola package has quartz crystal, integrated circuit, and
Patek Philippe, the noted Swiss watch and clock manufacturer, is employing COS/MOS
circuits in a timing system whose clocks can automatically switch over to small
batteries in the event of a primary power source failure. This assures continued
operation and eliminates the need for resetting numerous clocks in a large facility.
The system is designed for factories, schools, hospitals, and other facilities where
uninterrupted precision time keeping is a must.
Innovative applications such as this, combined with mass marketing of the electronic
watch, are giving electronic timekeeping an increasingly important everyday role.
It appears certain that by 1980 the electronic watch will dominate that part of
the market consisting of watches in the over-$50 price range. In attaining this
status, the electronic watch will enable solid-state technology to participate in
a total worldwide market in which all types of watches are expected to sell at the
rate of 300-million units annually by 1980.
How far the electronic watch sales penetrate into other segments of the market
will depend to a large degree on how much the prices of electronic components call
be reduced. Today, four-fifths of all watches sold in the U.S. are priced at $40
or less. Should component prices drop low enough to allow an all-electronic watch
to appear on the market for $40 or less, there will be a corresponding increase
in the electronic watch's segment of the overall market.
Electronic timekeeping is here now, but it is only recently on the scene. There
is still much research and development to be undertaken before a "universal" electronic
system is devised. Even so, the electronic watch has already established one fact
of central importance to the consumer: The age of near-perfect timekeeping has arrived.
Perhaps, if all goes well (and there is no indication that it will not), there is
an electronic wristwatch in your future.
Posted February 19, 2020