US3756013A - Solid state watch - Google Patents

Abstract

Disclosed is a solid state watch which requires no moving parts for timekeeping and display. The watch comprises a crystal controlled oscillator connected through an intergrated circuit binary frequency divider to an electro-optical display in the form of light emitting diodes. The display is energized only on demand and the level of the light output is controlled in accordance with ambient light conditions. The watch is energized from a rechargeable battery.

Description

United States Patent [1 1 Bergey et al.

I SOLID STATE WATCH [75 Inventors: John M. Bergey; Richard S. Walton,

both of Lancaster. Pa.

I73 I Assignee: HMW Industries, Inc., Lancaster,

[22] Filed: Apr. 20, 1972 [2] Appl. No.: 245,960

Related U.S. Application Data [62] Division of Ser. No. 35,l96, May 6, 1970, Pat. No.

I52] U.S. Cl. 58/50 R, 58/4 A, 58/23 R, I 58/23 A, 58/38, 58/39.5, 58/85.5 I51 I Int. Cl. G04b 19/30, G04b 27/00 I58] Field of Search 523/23 R, 23 A, 50 R,

Sit/85.5, 4 A, 38, 39.5; 235/92 T, 92 CP, 92 EA; 307/225 R, 225 C 4 1 Sept. 4, 1973 Primary Examiner-Richard B. Wilkinson Assistant Examiner-Ed ith C. Simmons .laclcmon Attorney-Robert E. Le Blanc, Leonard F. Stoll et al.

[57] ABSTRACT Disclosed is a solid state watch which requires no moving parts for timekeeping and display. The watch comprises a crystal controlled oscillator connected through an intergrated circuit binary frequency divider to an electro-optical display in the form of light emitting diodes. The display is energized only on demand and the level of the light output is controlled in accordance with ambient light conditions. The watch is energized '56] References Cited from a rechar eable batter UNITED STATES PATENTS g 3,304,415 2/l967 Connolly et al 235/92 T 13 Claims, 26 Drawing Figures K a 28 f 32 DISPLAY FREQ. i FREQ, ACTUATNG STANDARD CONVERTER MEANS mtmmssr 4515 3756013 sum '01 or 1s PATENTEDSEP 41m 3.756013 SHEET 02 0F 15 2 FIG. 2 Q 34 S 2(8 32 FREQ. FREQ DISPLAY STANDARD CONVERTER JEQL' \IB FIG. 5

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ELM??? 7+I SEGMENT DISPLAY g UNITS TENS g NI TENS E8 Q Q Q Q o RsTuvwxYc O 0 o o o o l I. l I I I o o I I o o o o I 0 I o o o o o I 0 o o o 2 I I o l I o I o I l I o o o 3 I I I I o o I o I o o I o o 4 o l l I o l I o I I o I o 0 5 I o I l o I I o l o o 0 o o o I I I I l I o o I- o o o o I o l I o o o o 0 I o l o o o 2 l I o l I o l o I SOLID STATE WATCH This application is a voluntary division of our copending application Ser. No. 35,196 filed May 6, I970 for SOLID STATE WATCH, now U.S. Pat. No. 3,672,l55.

This invention relates to a solid state timepiece and more particularly to an electric watch which employs no moving parts. In the present invention, a frequency standard in the form of a crystal oscillator acts through solid state electronic circuit dividers and drivers to power in timed sequence the light emitting diodes of an electro optic display. Low power consumption and small size and weight are achieved through the use of complementary MOS circuits to produce what is in essence a miniaturized fixed program computer.

Battery power Wristwatches and other small portable timekeeping devices of various types are well known and are commercially available. The first commercially successful battery powered wristwatch is of the type shown and described in assignees U.S. ReissuePat. No. RE.26,187, reissued April 4, 1967 to John A. Van Horn et al. for ELECTRIC WATCH. Electric watches of this type employ a balance wheel and a hairspring driven by the interaction of a current carrying coil and a magnetic field produced by small permanent magnets.

ln recent years, considerable effort has been directed toward the development of a wristwatch which does not employ an electromechanical oscillator as the master time reference. In many instances, these constructions have utilized a crystal controlled high frequency oscillator as a frequency standard in conjunction with frequency conversion circuitry to produce a drive signal at a suitable timekeeping rate. However, difficulties have been encountered in arriving at an oscillatorfrequency converter combination having not only the required frequency stability, but also sufficiently low power dissipation and small size to be practical for use in a battery powered wristwatch. T

In order to overcome these and other problems, there is disclosed in assignees copending U.S. application Ser. No. 768,076, filed Oct. 16, 1968, now U.S. Pat. No. 3,5 60,998 a crystal controlled oscillator type watch construction using low power complementary MOS circuits. The oscillator-frequency converter combination of that application as described is suitable for driving conventional watch hands over a watch dial or, alternatively, for selectively actuating the display elements of an optical display in response to the drive signal output of the converter.

ln assignees copending U.S. application Ser. No. 818,228, filed April 22, 1969, now U.S. Pat. No. 3,576,099 there is disclosed an improved watch construction in which the optical display takes the form of a plurality of light emitting diodes which are intermittently energized on demand at the option of the wearer of the watch. This assures a minimum power consumption and an increasingly long life for the watch battery.

The present invention is directed to an improved watch construction of the same general type as disclosed in the aforementioned copending applications and one which utilizes no moving parts to perform the timekeeping function. The watch of the present invention consists of only three major components, namely a quartz crystal time base, a miniature time computer module, and a rechargeable battery. These microminiature components are packaged in a conventional size wristwatch chassis or case. A tiny quartz slab is precisely cut to predetermined dimensions so that it vibrates at 32,768 Hz when properly stimulated by pulses from an electronic oscillator. The high frequency from the crystal time base is divided down to 1 pulse per second by utilizing a multistage, integrated circuit binary counter. The time computer module counts the input pulse train, encodes it into binary form, and then decodes and processes the results so as to provide the appropriate signals at display stations.

Situated on the front of the watch adjacent the display is a pushbutton demand switch which, when pressed, instantly activates the appropriate visual display stations. Minutes and hours are programmed to display for 1% seconds with just a touch of the demand switch. Continued depression of this switch causes the minute and hour data to fade and the seconds to immediately appear. The seconds continue to count as long as the wearer interrogates the computer module. Computation of the precise time is continuous and completely independent of whether or not it is displayed.

Incorporated in the watch case is a miniature 3 or 4% V rechargeable battery which is easily replaced by the wearer. The battery will last about 5 or 6 months under average wearing conditions before recharging becomes necessary and need for replacement is indicated by a dim display but the timing accuracy of the watch is not affected by the reduced capacity power supply. Each watch is sold with an extra rechargeable battery connected through a recharging circuit to provide the correct recharging current. The spent battery is simply removed by the wearer and replaced by the fully recharged spare. No computed time is lost in this battery exchange since a third energy source permanently lo cated inside the electronic module supplies sufficient power to run the time computer module during the exchange cycle.

The watch display consists of a T.V. screen-like colored filter which passes the cold red light from GaAsP light emitting diodes. A 27 dot or, alternatively, a 7 segment array forms each individual number at the appropriate moment at a brightness determined by a specially designed dimmer circuit. This dimmer circuit utilizes photodetectors to measure ambient lighting conditions so the display intensity provides viewing comfort under all day or nighttime lighting conditions.

Setting is accomplished quickly and accurately by inserting any suitable probe (pencil, pen, small stick, etc.) into one of two clearly marked recesses. The Hour Set rapidly advances the hours without disturbing the accuracy of the minutes or seconds. The Minute Set automatically zeros the seconds while it advances the minutes to'the desired setting. The whole procedure, even though seldom required, takes a matter of a few seconds.

The watch of the present invention is virtually shockproof and waterproof, regardless of the environment in which it is placed. The computer module, including the display, is encapsulated with a clear potting compound so that no mechanical forces or corrosive elements can attack the electronics. Since there is no conventional stem for winding or setting, the small shaft sealing problem is eliminated. No maintenance or repair is normally necessary since all three ingredients are individually sealed and inaccessible to influences from the outside world. All solid state electronic components, in-

3 cluding the light emitting diode displays, have a virtually unlimited life.

It is therefore one object of the present invention to provide an improved electronic wristwatch.

Another object of the present invention is to provide a wristwatch which utilizes no moving parts for performing the timing function.

Another object of the present invention is to provide a completely solid state electronic wristwatch in which the display is in the form of a plurality of light emitting diodes.

Another object of the present invention is to provide an electronic watch including an illuminated display in which the light level is automatically compensated to the viewing conditions for increased eye comfort and reduced power drain.

Another object of the present invention is to provide an improved electronic watch in which the display is automatically programmed such that the hours and minutes disappear at a predetermined period of time and the seconds display comes into view.

Another object of the present invention is to provide an improved wristwatch incorporating an electro optic display with an improved arrangement for resetting the display and one which includes automatically zeroing of the seconds display.

Another object of the present invention is to provide an improved electronic wristwatch incorporating a rechargeable battery.

Another object of the present invention is to provide an improved wristwatch having a permanent internal sustaining battery or the like so that no timekeeping is lost when the battery is replaced.

Another object of the present invention is to provide a wristwatch size device which functions as a fixed program computer.

These and further objects and advantages of the invention will be more apparent upon reference to the following specification, claims, and appended drawings, wherein:

FIGS. lA-lC are views of the face of a watch constructed in accordance with the present invention under differing conditions of operation;

FIG. 2 is a simplified block diagram of the major components of the solid state watch of this invention;

FIG. 3 is an exploded view showing the physical construction of the novel solid state watch of this invention;

FIGS. 4, 4A and 4B are overall block diagrams of the electrical circuit for the solid state watch of FIG. 3;

FIGS. 5, 5A, 5B and 5C are detailed wiring diagrams for the watch of FIG. 3;

FIG. 6 shows a plurality of waveforms illustrating the operation of the light dimmer forming a part of the watch of FIG. 3;

FIG. 7 shows the details of one of the decoder drivers forming a part of the electrical circuit of the watch of FIGS. 3-5;

FIG. 8 shows a modified crystal controlled oscillator circuit for the watch of the present invention utilizing complementary MOS circuits;

FIG. 9 shows a modified display element for the watch of the present invention in the form of a 7 bar segment construction of light emitting diodes;

FIG. 10 is a detailed wiring diagram for a modified watch construction utilizing the display of FIG. 9 in which the programmable counter and decoder for the 7 segment display are all formed on a single monolithic integrated circuit chip;

FIG. 10A is a table showing the connections to the power supply terminals A and B in FIG. 10 when the circuit of FIG. 10 is used for difi'erent display digits;

FIG. 103 shows the alphabetical nomenclature for the 7 bar segment diodes R through W of a ones" digit and the corresponding diode Y of the tens" digit in the hours display;

FIG. 11 shows waveforms at various locations in the circuit of FIG. 10 when it is used to count to 12 (1-12) for the hours display;

FIG. 12 shows similar waveforms for the circuit of FIG. 10 when it is used to count to 10 (0-9) for the ones digits of the minutes and seconds display;

FIG. 13 shows corresponding waveforms for the circuit of FIG. 10 when it is used to count to 6 (0-5) for the tens" digits of the minutes and seconds display;

FIG. 14 is a waveform and timing diagram for the BCD to decimal decoder forming a part of the circuit of FIG. 10;

FIG. 15A is a table showing the relationship between the input signals, the BCD output of the counter (counting 1-12) and the 7 diode segments (8 segments with the tens l) for the hours display;

FIG. 15B is a similar table showing the relationship when the counter is counting to 10 (0-9); and

FIG. 15C is a corresponding table for when the counter is counting to 6 (0-5).

Referring to the drawings, the novel watch of the present invention is generally indicated at 10 in FIG. 1A. The watch is shown in FIG. 1A to actual size and is constructed to fit into a watch case of approximately the size of a conventional mans wristwatch. The case 12 is shown connected to a wristwatch strap 14 and includes a display window 16 through which the time is displayed in digital form and a pushbutton 18 for operating a demand switch through which the display is activated.

FIG. 1A shows the watch as it normally appears when the time is not being displayed. That is, in FIG. 1A no time indication is visible through window 16 and this is the normal condition which prevails in order to conserve battery energy in the watch. However, even though the time is not displayed through the window 16, it is understood that the watch 10 continuously keeps accurate time and is capable of accurately displaying this time at any instant of the day or night. When the wearer desires to ascertain the correct time, he depresses pushbutton 18 with his finger and the correct time immediately is displayed through the window 16 which illustrates a dot display giving the correct time reading as 10:10, namely I0 minutes after 10 oclock, as indicated at 20 in FIG. 1B. The hours and minutes, i.e., l0:10, are displayed through the window 16 for a predetermined length of time, preferably 1% seconds, irrespective of whether or not pushbutton 18 remains depressed. The exact time of the display is chosen to give the wearer adequate time to consult the display to determine the hour and minute of the time. Should the minutes change during the time of the display, this change is immediately indicated by advancement of the minute reading to the next number, i.e., l l, as the watch is being read. If pushbutton 18 remains depressed, at the end of 1% seconds, the hours and minutes of the display are extinguished, i.e., they disappear, and simultaneously the seconds reading, i.e., 59,

is displayed through the window l6 as indicated at 22 in FIG. IC. The advancing seconds cycling from 0 to 59 continue to be visible through window 16 until the pushbutton 18 is released.

FIG. 2 is a simplified block diagram of the electrical circuitry for the watch of FIG. 1. The circuit comprises a time base or frequency standard 26 including a crystal to provide a very accurate frequency such that the frequency standard or oscillator oscillates at 32,768 Hz. This relatively high frequency is supplied by lead 28 to a frequency converter 30 in the form of a divider which divides down the frequency from the standard so that the output from the converter 30 appearing on lead 32 is at a frequency of 1 Hz. This signal is applied to a display actuator 34 which, in turn, drives the displays 20 and 22 of the watch by way of electrical lead 36.

FIG. 3 is an exploded view showing the physical construction of a watch formed in accordance with the present invention. Watch 10 in FIG. 3 comprises the casing 12 carrying the pushbutton or display button 18 and provided with a window 16 through which the display may be read. Inserted into the window 16 and sealed there by a suitable epoxy resin is a light filter 38 which screens out much of the light which might otherwise get through the window. Of course, the filter 38 may be formed of a clear transparent material which passes all light but in the preferred embodiment it takes the form of a suitable red colored plastic, such as Plexiglas, which acts as a red filter (bandpass) passing light from the light emitting diodes of the display which, by way of example only, operate at a wave length of approximately 6,500 Angstroms in the visible red region. In some instances, it may be desirable to construct the filter 38 to pass blue as well as red wave lengths so that the blue of the sky gets absorbed in the watch, thus enhancing somewhat visibility of the lighted numbers under outdoor daytime reading conditions. The filter 38 may be formed of any suitable material, in addition to plastic, such as transparent colored glass or of ruby material having sufficient hardness that it will not scratch.

Received within case 12 are a pair of abutting backto-back shims (shown separated for the sake of clarity), namely, a display shim 40 and a logic shim 42. The shims are preferably formed of a good strong heat conducting material, such as beryllium copper to take away any heat that might be generated by the display. Mounted on the underside of the logic shim 42, as indicated by phantom lines at 44, is the integrated logic circuitry. Secured to the top surface of display shim 40 are six display modules 46, 48, 50, 52, 54 and 56. Display modules 46 arid 48 are for displaying the hours from I to 12, modules 50 and 52 are for displaying the minutes from 0 to 59, and modules 54 and 56 are for displaying the seconds from 0 to 59. Each of the modules is formed as a 27 dot array, i.e., each carries 27 light emitting diodes with the exception that minute module 50 carries the additional colon diodes 58 and hours tens digit module 46 carries only sufficient diodes to display a l that is the tens digit of the hours display is either 1 or 0 and 0 is not illuminated. While a 27 dot array is illustrated, the display modules may take any desired form and may consist of a 13 dot array or a 7 segment bar array as disclosed in copending application Ser. No. 818,227, filed Apr. 22, 1969. By way of example only, the 27 dot array illustrated in FIG. 3 may be formed on modules of the type manufactured by the Hewlett-Packard Company of Palo Alto, Calif, identified as solid state numeric indicator HP 5082-7000. These modules have the light emitting diodes mounted on them and are formed of a ceramic base with integrated circuit chips such as the chips 60, 62, 64, 66 and 68 mounted on the ceramic base and connected to the diodes and the logic circuits by suitable leads, laminated, printed or etched directly on the ceramic substrates. Connection from the display modules to the logic circuit 44 is by way of leads 70 which extend over the adjacent edges of the display shim 40 and the logic shim 42. In the preferred embodiment, the display modules are made slightly narrower than is customary for solid state numeric indicators but they are in all other respects similar to the commercially available solid state numeric indicators identified above.

While two separate shims are illustrated, it is understood that by using suitable monolithic integrated circuit constructions it is possible to mount the logic circuits and display circuits on the top of a single shim, thus eliminating the necessity for the second shim illustrated in FIG. 3. In the preferred embodiment, the dis play shim and the logic shim with the respective circuits attached are potted by coating the upper surface of shim 40, the shim edges and the lower surface of shim 42 with a clear silicone rubber potting compound. This isolates the electronics from the surrounding environment and enhances the reliability of operation of the circuits.

Depending from the underside of logic shim 42 is a quartz crystal 72 which, when the watch is assembled, is adapted to project into the opening 74 of a quartz crystal pocket 76 attached to electronic seal cover 78. Seal cover 78 carries a second pocket 80 which pennanently receives a small internal sustaining power source or battery for maintaining the timing operation of the watch when the main battery is removed for replacement and recharging.

Mounted on back cover 82 of the watch is a battery case 84 which houses a conventional rechargeable 4% V silver zinc battery (not shown). The battery may be of a 3 1% V cell construction to give a total battery output of 4% volts with a life of approximately 250 milliampere hours. Assuming standard usage, i.e., an average of approximately 24 interrogations per day, the battery will last on the order of 5 or 6 months before recharging is necessary. The battery employs a potassium hydroxide electrolyte and batteries of this type are commercially available from Yardney, Inc. of New York City. Power is supplied from the battery in case 84 by way of a pair of pins 86 and 88 which slide into receptacles 90 and 92 in the battery case to make contact with the battery and the upper ends of which contact with the electrical circuitry on the underside of logic shim 42. Resetting is effected by a pair of two-part reset pins extending through the back cover of the watch, the two parts of one of the reset pins being illustrated at 92A and 928 in FIG. 3. Finally, the various elements of the watch are mechanically secured together by the screws 94.

It is a feature of the watch 10 that the substrates of the display modules are removably attached to the upper surface of display shim 40. That is, the substrates of the display modules 46, 48, 50, 52, 54, and 56 are attached by Bordens epoxy to the shim, which epoxy softens at about 300 F. and permits removal of the display modules from the shim for repair or replacement. The light emitting diodes mounted on the substrates are interconnected with the remaining circuitry by 0.001 inch aluminum wires ultrasonically bonded for interconnection.

FIGS. 4, 4A and 4B show an overall block diagram of the electrical circuit of the watch of the present invention. Watch 10 comprises an oscillator 96 which is controlled by the crystal 72 of FIG. 3 to produce an output on lead 98, i.e., a pulse train on that lead having a pulse repetition rate of 32,768 Hz. The crystal output passes through a complementary symmetry MOS counter 100 of the type shown and described in assignee's copending application Ser. No. 768,076, filed Oct. [6, 1968, now U.S. Pat. No. 3,560,998 which acts as a divider, dividing the output by 2', s a 7 Stage counter, to produce an output on lead 102 having a pulse repetition rate of 256 Hz. This signal is divided by 2 in counter 104, by 2 again in counter 106, by 8 (2) in counter 108, and by 4 (2") in counter 110.

An 8 Hz. output on lead 112 from counter 108 is applied to a set-hold circuit 114 where the 8 Hz. repetition rate pulse train appears as an output on lead 116. The 8 Hz. signal on lead 116 is applied to a counter 118 where it is divided by 8 (2) to produce a 1 Hz. output pulse train on lead 120. The 1 Hz. pulse train is divided by 10 in counter 122, divided by 6 in counter 124, divided by 10 again in counter 126, divided by 6 again in counter 128, and the output of this counter is finally applied to counter 130 which divides by 12. The output of counter 122 appearing on leads 132, 134, 136, and 138 is a binary coded decimal 1248 code which is applied to the decoder-driver 140 which, in turn, energizes the tens digits of the seconds display indicated at 142. The ones digits of the seconds display indicated at 144 are similarly actuated from counter 124 by way of seconds decoder-driver 146. Similar decoder- drivers 148, 150, and 152 actuate the tens digits of the minutes display at 154, the ones digits of the minutes display at 156, and the hours display at 158. Counter 130 has five output leads to decoder-driver 152 fo a purpose more fully described below. The other decoder-drivers 146,148 and 150 are actuated by BCD i248 codes from their respective counters 124, 126, and 128 in the same manner as decoder-driver 140 is actuated from counter 122.

As previously stated, in order to conserve energy, the light emitting diodes are only energized on demand, i.e., when the pushbutton 18 of FIGS. lA-lC is depressed by the wearers finger. Even when the button is depressed, the lights are not always continuously lit but instead, in order to conserve power, are intermittently lighted during less than full daylight conditions at a frequency sufficiently high to give the appearance of continuity due to the light retention properties of the human eye. The pulses for intermittently lighting or pulsing the seconds display are derived from a display control driver 160 which applies the on-off pulses by way of lead 162 to the seconds decoder- drivers 140 and 146. Similar intermittent pulses from the display control drivers 160 are applied by lead 164 to the minutes decoder- drivers 148 and 150 and by lead 166 to the hours decoder-driver 152. The exact frequency at which the displays are turned on and off while always sufficiently high to give the impression to the human eye of continuous light is determined by a light control circuit 168 which supplies a light control signal by lead 170 to display control drivers 160. The light control signal is either DC (full daylight) or a combination of a 64 Hz. signal supplied from counter 106 by way of lead 172, a 128 Hz. signal supplied by counter 104 by way of lead 174, and a 256 Hz. signal supplied from the output of counter by way of lead 176. These signals are combined in the light control circuit 168 in a manner determined by the output signal on lead 178 to the light control circuit from ambient light sensors 180. These light sensors are in the form of three phototransistors mounted on the display shim at 40 in FIG. 3 and act to produce increased illumination from the light emitting diodes during strong daylight conditions and less illumination from the diodes under nighttime or reduced light conditions. In the preferred embodiment, light sensors 180 provide four different light levels from the light emitting diodes so that the watch face may be read with equal facility and comfort under all possible lighting conditions while at the same time conserving energy at times when less light is needed from the diodes to make them visible, such as is the case when the watch is read in at least partial darkness.

As previously stated, the watch face is ordinarily not illuminated. The hours and minutes diodes only light up when the demand switch is depressed. Actuation of the demand button by the wearer causes the read switch 184 in FIG. 4 to close, causing the positive side of the power supply to be connected by way of leads 186 and 188 to the display control drivers 160. Energization of these drivers permits passage through them of the signal from the light control circuit 168 which is passed on to the decoder-drivers causing the minutes and hours displays to be illuminated. No output from the display control diodes 160 appears on lead 162 at this time and the seconds displays are not illuminated. Closure of read switch 184 also applies B+ by way of lead 190 to set-hold circuit 114 which immediately resets a display timer 192 by way of lead 194. Display timer 192 is a divide by 10 counter and has applied to its input the 8 Hz. pulse train on lead 112. This timer divides the 8 Hz. by 10 and after 1% seconds produces an output pulse on lead 196 which is applied to display control driver 160. This pulse causes the display control driver to change state, removing the output from leads 164 and 166 and causing the minutes and hours displays to be extinguished. At the same time, the output is switched to lead 162 causing the seconds display to be illuminated simultaneous with the extinguishment of the hours and minutes display.

An important feature of the watch of the present invention lies in the fact that the hours may be set independently of the minutes and seconds and at a very rapid rate. Closure of hours set switch 198, which is actuated from the back cover of the watch by a double pin setting arrangement of the type illustrated at 92A and 928 in FIG. 3 grounds one input of an hours set circuit 200 by way of leads 202 and 204. Hours set circuit 200 receives a 2 Hz. pulse train from counter by way of lead 206 and actuation of the hours set circuit by closure'of hours set switch 198 causes the hours set circuit 200 to pass the 2 Hz. signal on lead 206 to counter by way of lead 208. Hours set switch 198 is also connected to the display control drivers to cause an utput to appear on leads 164 and 166 assuring that the hours and minutes are displayed when the hours are being reset during closure of switch 198. A minute set switch 212 is connected by leads 214 and

Claims (13)

1. A wristwatch comprising a source of frequency controlled electrical timing signals, a first divider coupled to said source for lowering the frequency of the timing signals to a frequency greater than 1 Hz, a resettable divider coupled to saiD first divider for lowering the frequency of said timing signals to 1 Hz, seconds, minutes and hours counters coupled to said resettable divider for producing electrical time display signals, an electro-optical digital time display coupled to said counters, minutes setting means coupled to said minutes counter, and means coupling said minutes setting means to said resettable divider for resetting said divider when said minutes setting means is actuated.

2. A wristwatch according to claim 1 wherein said seconds counter is resettable, and means coupling said minutes setting means to said seconds counter for resetting said seconds counter when said minutes setting means is actuated.

3. A wristwatch according to claim 2 wherein said minutes setting means comprises a switch, a restart switch, means coupling said minutes setting switch to said resettable divider and said seconds counter for disabling said resettable divider and said seconds counter in response to actuation of said minutes setting switch, and means coupling said restart switch to said resettable divider and said seconds counter for re-enabling said resettable divider and said seconds counter in response to actuation of said restart switch.

4. A wristwatch according to claim 3 wherein said restart switch comprises a display demand switch.

5. A wristwatch according to claim 3 including a set-hold circuit coupling said minutes setting switch and said restart switch to said resettable divider and said seconds counter.

6. A wristwatch according to claim 3 including a minute set circuit coupling said minutes setting switch to said minutes counter for applying a signal greater in frequency than 1 Hz to said minutes counter in response to actuation of said minutes setting switch.

7. A wristwatch according to claim 6 wherein said greater frequency signal is applied to said minutes counter as long as said minutes setting switch is actuated.

8. A wristwatch comprising a source of frequency controlled electrical timing signals, a first multi-stage binary chain divider coupled to said source for lowering the frequency of the timing signals to a frequency greater than 1 Hz, a resettable divider coupled to said first divider for lowering the frequency of said timing signals to 1 Hz, a divide by 60 seconds counter, a divide by 60 minutes counter and a divide by 12 hours counter all coupled to said resettable divider for producing electrical time display signals, said counters being formed as binary chains to produce time display signals in binary coded decimal form, a decimal electro-optical time display coupled to said counters, a minute set switch coupled to said minutes counter for advancing said minutes counter in response to operation of said minute set switch, means coupling said minute set switch to said resettable divider and said seconds counter for resetting and holding the reset state of said resettable divider and said seconds counter in response to actuation of said minute set switch, a restart switch, and means coupling said restart switch to said resettable divider and said seconds counter for releasing them from said reset state in response to actuation of said restart switch.

9. A wristwatch according to claim 8 including an hour set switch, and means coupling said hour set switch to said hours counter for advancing said hours counter in response to actuation of said hour set switch.

10. A wristwatch according to claim 8 wherein said resettable divider comprises a three stage binary dividing chain.

11. A wristwatch according to claim 8 including means for applying a 2 Hz advancing signal to said minutes counter as long as said minute set switch is actuated.

12. A wristwatch according to claim 8 wherein said electro-optical display comprises a plurality of light emitting diodes forming seconds, minutes and hours display stations, and a bi-polar driver transistor coupling said counters to said light emitting diodes.

13. A Wristwatch according to claim 12 including a complementary MOS inverter coupling said counters to said bi-polar driver transistor.

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