A revolution in timekeeping has occurred in the past few years. We've seen the appearance of the electric watch; then the electronic watch and digital clocks - and now a digital wristwatch.

The newest timepiece is the Hamilton Pulsar, a solid-state, time-indicating wrist computer. It's an all-electronic timepiece that has no moving parts. Instead, it is made up of three major electronic sections:

1. A rechargeable 3-cell 4.5-volt battery
2. A high-frequency quartz crystal
3. A computer module with microminiature logic and display circuits

The high-energy main battery, which takes up 80% of the total volume of the case, excites a quartz crystal, which oscillates at 32,768 Hz. This battery also maintains the charge in a similar, but much smaller, sustaining battery that continuously drives the logic circuitry. The main battery measures a mere 1.035 x 1.4 x 0.196 inches.

The computer's integrated circuits, hybrid-circuit logic substrates, display substrates and all wiring are ultrasonically bonded and mounted on separate gold-plated shims plates of 0.015-inch thick beryllium copper. The shim plates with their circuitry are screwed together, back-to-back, and form a fixed-program computer about a tenth of an inch thick. The assembly is potted in epoxy for physical protection and cannot be jarred out of order.

The logic circuitry consists of seven individual hybrid circuits that contain 44 complementary-symmetry metal-oxide semiconductor (MOS) integrated circuits. They are equivalent to 3,474 npn and pnp transistors.

The oscillator and countdown circuit generates the primary frequency and divides it down by a factor of two. The 14-stage divider provides five different frequencies for various functions, which are fed to other circuits.

The operational control circuit times the length of display of the hours and minutes digits, which is set at 1 1/4 seconds, on command, when the push button on the face of the timepiece is depressed. The same logic circuit supplies a signal that causes the seconds display to light following the minutes display if the pushbutton is held down. A third function of this circuit is to control the setting of the minutes display. Setting the minutes, in turn, generates a signal to reset the seconds to zero, thus stopping the display circuits until the timepiece is restarted. This does not interrupt the accurate timekeeping capability of the logic circuits, since the oscillator keeps running.

Another logic substrate, the seconds counter circuit, counts the seconds and allows for zeroing the seconds display. It also generates the signal that makes the minutes display change from 59 to 00 at the proper times.

The minutes counter counts the minutes and generates a signal that causes the hours display to change from 12 to 1 in a 12-numeral sequence.

The hours circuit counts the hours from 1 to 12.

An automatic light-level control supplies signals to three light sensors that are mounted on the display assembly. These sensors measure ambient light levels. As ambient light gets brighter, the sensors lengthen the duty cycle of the light emitting diodes (LED's) that form the numerals, this giving the effect of increased brightness to make the numbers easier to read in daylight.

The last of the logic circuits is the power switching circuit. It supplies power to six display decoders. These units, one for each digit, are fed the BCD (binary coded decimal) information from the counter circuits and convert these pulses into numbers.

The LED's, measuring 0.021-inch square, are arranged in 27-dot matrices, one for each numeral. One of these matrices, however - the tens digit of the hours display - needs only seven diodes to form the numeral 1.

This timepiece has extremely high accuracy, since its basic operating frequency is four times greater than that used in electromechanical quartz-crystal watches. This makes it possible to keep time deviation to less than 3 seconds per month. In addition, since there is no mechanical gear train, the electronic timepiece is not affected by its physical position. This does have a great effect on the accuracy of standard electronic watches.

The three-cell rechargeable battery was specifically designed and built for this application. Under normal use it will power the Pulsar timepiece for up to six months. The timepiece comes with a spare battery and recharger. The spent battery is removed by unscrewing the back of the case and the fully charged spare is inserted. No accuracy is lost when batteries are changed. There is a second battery permanently located inside the electronic module that will provide power while the main battery is replaced.

One of the most important features of the Pulsar is that since it has no moving parts, nothing can fail because of friction or wear. As a further assurance of durability, all components, including wires, are potted. Since there is no conventional stem for winding or setting, the stem-sealing problem is totally eliminated, making it relatively easy to waterproof the timepiece.

Should it be necessary to set the time, all the owner needs to do is depress one of the two marked recesses on the rear of the case. One recess rapidly advances the hours without disturbing either the minutes or the seconds. The other recess automatically sets the seconds reading at zero while advancing the minutes.

For those interested in a brief history of telling time, the first recorded instance of time-telling by measured flow occurred in China over 4,000 years ago. The Emperor, Hwangti, invented a water clock consisting of a pierced brass bowl floating in a basin of water. Hours were calculated by the amount of time it took the bowl to submerge.

Later, the Greeks developed and refined the Clepsydra (water clock). In other parts of the world, forerunners of the hourglass were being devised.

During the Crusades, mechanical time contrivances, operated by weights were brought to Europe from the East. In 1480, Peter Henlein, a Nuremberg locksmith built a portable, mechanical spring-driven timepiece. It had a single hand to tell the hours. The first wristwatch appeared in 1571. In 1670 a minute hand was added and in 1685, the balance wheel, a must in an accurate watch.

By contrast today we have the Pulsar.