US3765163A

US3765163A - Electronic timepiece

Info

Publication number: US3765163A
Application number: US00235608A
Authority: US
Inventors: Levine M Meyer; Cake A Fischer
Original assignee: URANUS ELECTRONICS
Current assignee: URANUS ELECTRONICS; URANUS ELECTRONICS INC US
Priority date: 1972-03-17
Filing date: 1972-03-17
Publication date: 1973-10-16
Anticipated expiration: 1990-10-16

Abstract

An all electronic direct digital read-out timepiece employing a matrix of light emitting diodes which are user actuated to provide a display of the time in response to their actuation. A first demand switch provides a display of hours and minutes. A second demand switch provides a display of time in seconds using the same light emitting diodes as are used for the first display. When the display is turned on, it cycles through three levels of light intensity each lasting a predetermined time period of approximately one second after which the display automatically turns off. The time is set through the actuation of a single time setting switch in addition to the display demand switch. Through successive manipulations of the display demand switch, the time may be set at any predetermined value in advance of the real time, time keeping may be suspended until the real time catches up with the time set, and when the time set is coincident with real time time keeping may be reinstated. The design of the system provides for minimum current drain so that a small watch having reasonable battery life is provided.

Description

United States Patent Levine et a1.

[11] 3,765,163 [451 Oct. 16, 1973 ELECTRONIC TIMEPIECE Inventors: Morris Meyer Levine, Scarsdale;

Arthur Fischer Cake, Smithtwon, both of N.Y.

211 App]. No.: 235,608

[52] US. Cl. 58/50 R, 58/23 A, 58/23 BA, 58/85.5 [51] Int. Cl. G04b 19/30, G04b 27/00 [58] Field of Search 58/23 A, 23 R, 23 C, 58/23 AC, 23 BA, 50 R, 85.5; 340/3094 [56] References Cited UNITED STATES PATENTS 3,457,524 7/1969 Adler 58/23 R X 3,626,686 12/1971 Harris 58/23 R 3,646,751 3/1972 Purland et al 58/152 R 3,576,099 4/1971 Walton 53/23 R 3,668,860 6/1972 Diersbock 58/23 BA 3,672,155 6/1972 Bergey et al. 58/50 R Primary ExaminerRichard B. Wilkinson Assistant Examiner-Edith C. Jackmon ArtorneyRyder, McAulay and Hefter [S 7] ABSTRACT An all electronic direct digital read-out timepiece employing a matrix of light emitting diodes which are user actuated to provide a display of the time in response to their actuation. A first demand switch provides a display of hours and minutes. A second demand switch provides a display of time in seconds using the same light emitting diodes as are used for the first display. When the display is turned on, it cycles through three levels of light intensity each lasting a predetermined time period of approximately one second after which the display automatically turns off. The time is set through the actuation of a single time setting switch in addition to the display demand switch. Through successive manipulations of the display demand switch, the time may be set at any predetermined value in advance of the real time, time keeping may be suspended until the real time catches up with the time set, and when the time set is coincident with real time time keeping may be reinstated. The design of the system provides for minimum current drain so that a small watch having reasonable battery life is provided.

15 Claims, 3 Drawing Figures 54 36 40 4 70 Gar-cs X2 G/arss x I Z. 72 2 I no m LSD mm 44 46 +10 on]; +6 +10 +6 1-12 2 +10 -4 4F SFF 4FF' aFF 4 F7 IFF 4 FF I ZFF :6 Q o 17' -14 K Lag ELECTRONIC TIMEPIECE This invention relates in general to an electronic timepiece, and more particularly to one whose design and arrangement affords efficient display requiring minimum battery drain thereby providing low cost, small size and long life.

BACKGROUND OF THE INVENTION Electronic timepieces have long been looked to as the means for making a fundamental departure from the traditional mechanical escapement used in almost all timepieces. The enormous accuracy available from a crystal has long provided an appealing alternative to mechanical escapement. The difficulty has been that electronic designs, which require battery power, call for too great a drain on the battery. As a consequence, either a relatively large battery was required or the battery employed had to be replaced too often. There is no commercially practical compromise available between the weight and size of a large battery and the frequent replacement of a small battery. In addition, in both cases, excessive costs result as contrasted with the traditional mechanical timepieces. Thus these problems became particularly acute when electronic designs were considered in connection with the most common form of timepiece, the wristwatch and pocketwatch.

Electronic time keeping circuits are known. One design is taught in U.S. Pat. No. 3,560,998, issued at Richard S. Walton. It is also known to provide direct digit read-outs of the use of light emitting diodes in such timepieces.

The development ofthe metal oxide silicon transistor made feasible the design of complementary-symmetry divide-down flip-flop timing circuits operating off a crystal output which draw current only at the flip-flop cross-over point and thus minimize battery drain. The timepiece illustrated in U.S. Pat. No. 3,560,998 employs this so-called COS/MOS type of design. The RCA CD 4007 integrated circuit is one usable building block employing COS/MOS.

However, for such timepieces to be practical, particularly for watch use, it is essential that the current drain be kept to a minimum. Minimum current drain means a better compromise between size of the battery necessary for the watch and the length of time that the battery will last before it needs replacement.

Accordingly, it is a major purpose of this invention to provide a direct digital read-out electronic timepiece having decreased current drain.

It is a related purpose of this invention to provide this decreased current drain characteristic in a design that involves a reasonably small volume and low weight circuit design and at a reasonable cost so that the long life between battery change and small battery size will be effected in a practical embodiment.

BRIEF DESCRIPTION OF THE INVENTION In brief, this invention is in an entirely electronic timepiece that is electronic from the crystal that supplies the basic frequency to the light emitting diodes that provide a direct digit display of the time. The only mechanical feature is a set of switches that are manually operated to turn on the light emitting diodes and thus provide a display of the time when desired and to set the time. To save on current drain, the same diode display matrix is employed to provide an hours and minutes display and to provide a date and seconds display, these displays being multiplexed through different display demand switches. To further save on current, a zener diode is employed to drop the battery voltage applied to the amplifier-oscillator operating off the crystal yet permitting adequate battery voltage for excitation of the light emitting diodes.

To provide the ability to use the timepiece in a wide range of ambient light conditions and to further save on current drain, there are three levels of intensity of the display which are cycled through from lowest to highest intensity automatically whenever the demand display switch is actuated.

A time setting mechanism is employed which is actu ated by the combination of a time setting switch and a display demand switch. A logic circuit is provided so that solely by successive manipulations of the display demand switch, the user of the watch can in succession set the time at some convenient point ahead of real time, stop the time setting while continuing to inhibit the normal time keeping so that the real time can advance to synchronization with the set time, then start time keeping once real time and set time are synchronized and finally, (all by actuation of the same display demand switch) view the time whenever desired.

BRIEF DESCRIPTION OF THE DRAWINGS that is employed with the time keeping mechanismillustrated in FIG. 1.

Although the automatic intensity control mechanism illustrated in FIG. 2 is essentially represented by a single block in FIG. 1, the time setting mechanism shown in FIG. 3 is essentially not represented in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Providing The Signals Representing Time FIG. I is a block diagram showing the basic arrangement ofa timepiece of this invention. An accurate crystal 10 having a precisely determined output frequency of, for example, 40,960 Herz (Hz.) provides the basic timing signal employed. An amplifier-oscillator 12 provides the basic timing signal with the amplitude sufficient to operate the various circuits in FIG. 1 and also in the form of a pulse train having a repetition rate equal to the frequency of the crystal 10.

The divide down circuit 14 is essentially sixteen bistable switching circuits, commonly called flip-flop (FF) circuits, the last four flip-flop circuits being connected in a divide by ten configuration The frequencies that can be tapped off. the divide down circuit 14 are a sub-multiple to the power of two of the basic crystal frequency, except that the final output frequency is a l Herz signal which is obtained in a known manner by appropriate feed back connections. This one Herz signal is applied to the first divide down circuit 18 in a series of divide down circuits. This I Herz signal is a 50 percent duty cycle pulse train having a pulse once per second.

The four flip-flops that constitute the divide down circuit 18 are interconnected so that they will cycle through ten separate states switching from state to state in response to an input pulse. Accordingly, every ten seconds the four interconnected flip-flops which constitute the divide down by circuit 18 will cycle through ten separate states and each state will have a duration of one second. The four outputs from the divide down circuit 18 will provide a binary coded decimal indication of the 10 states. This binary coded output, therefore, can be used to indicate the units digit of a decimal indication of seconds. The least significant digit (LSD) of this binary output will appear on the line so indicated and the state of that line (that is, wheter it has pulse or no pulse) will change once a second. The most significant digit (MSD) will appear on the line so indicated and the state of that line will cycle once every ten seconds. This most significant digit output is a 0.1 Herz pulse train and is also employed as the input to the next divide down circuit 20.

The divide down circuit 20 is a divide by six circuit, thus requiring only three flip-flops. ecause it is used to represent the tens digit of a decimal indication of seconds, the circuit 20 only has to represent six of the 10 decimal digits. This divide down circuit 20 as well as the rest of the divide down

circuits

22, 24, 26, 28, and 32 operate in a known fashion, are similar to that of the divide down circuit 18 and need not be described in much greater detail. The various divide down circuits 18 through 32 differ to some extent in the amount of division required. Thus, in FIG. 1, the amount of division performed by each circuit is indicated as is the frequency of that output from each divide down circuit which is supplied as the input to the next divide down circuit. The single flip-flop divide down circuit 28 is required because there are twelve hour sequences in each day. The input state change to the units digit for the date divide down circuit 30 has to be once a day rather than twice a day. Thus the pulse train representing the most significant digit in the hours digit divide down circuit 26 has to have its repetition rate divided by two before being applied as an input to the units of date divide down circuit 30. The single flip-flop 28 performs this function.

The binary coded decimal digit outputs from the divide down circuits 18 through 32 (except for 28) are all applied through respective normally closed sets of gates 34 through 46. These gates 34 through 46 are turned on (that is, enabled) by the signals indicated (W1, X1, Y1, Z1) or (W2, X2, Ygand Z2) 50 that each nary coded decimal digit is available for only a brief fraction of time as described below. When any one set of gates 34 through 46 is turned on, the output from the turned on set of gates are identical to their inputs. The outputs from the gates are indicated as outputs A, B, C and D to indicate the manner in which the outputs from the gates are connected as inputs to the binary to seven segment decoder 50. Only one of the seven sets of gates 34 through 46 is turned on at a time. Thus, the decoder 50 only has to cope with one input number at a time. Except for the hours number, each of these input numbers to the decoder 50 is a one digit decimal number.

Taking the units of seconds output as an example, when the set of four gates 34 is turned on, this output is applied to the decoder 50 as a four bit binary number. The decoder 50 converts this four bit number into a seven bit segment code. Each bit of the seven bit code is applied to a separate one of the normally off segment switches 8, through 5,. When the bit is high, the switch is turned on. When the bit is low, the switch remains in its normally off state. Each of four digit positions in the visual display 52 has seven segments. It is a well known technique to display a decimal digit by a seven segment digit position. By lighting up selected ones of these seven segments, any one of the 10 decimal numerals can be displayed. In one embodiment, each segment has four light emitting diodes (LEDs). Thus each position has 28 LEDs and the four positions require 112 LEDs.

Each of the segment switches S, through 5-, is connected between the positive terminal of a battery 54 and the anode of each of the four LEDs of a particular one of the seven segments of each of the four digits.

For example, if the output of the gate 34 at any one moment corresponds to the numeral 3, then five of the segment switches S through S will be turned on. Switch S for example, will connect the anodes of the four diodes at a first segment of each of the four positions to the battery 54. In effect, S will connect 16 LED anodes to the battery 54. When the units of seconds gates 34 output is applied to the decoder 50, it is essential to avoid turning on the LEDs representing the numeral involved in all four positions. With respect to this example, this means it is essential to turn on the appropriate LEDs only in the rightmost position; that is, the position that indicates the units of seconds. This result is achieved by virtue of the digit switches D through D.,. Each of these switches D through D, is connected between the cathodes of all the LEDs in a sepaeate one of the four digit display positions and, through an intensity control unit 56, to the negative terminal of the battery 54. For example, the switch D is connected to the cathodes of each of the 28 LEDs in the rightmost of the four digit positions. The signal W that opens the gate 34 is derived from a signal W that turns on the switch D With D turned on and with the appropriate five of the switches S through 5, turned on, the units numeral 3 will appear in the rightmost position of the display 52.

The representation of the digits for each of the other positions on the display operates essentially in the same fashion. There is a complication requiring additional gating so that the hours output from the gates 42 when applied-to the decoder 50 will permit representation of a two digit number when the hours are 10, l l, or 12. The technique for doing that will be described further on in this specification.

Sequencing of the Display Signals An important aspect of the arrangement of this invention is the sequencing of the various binary coded decimal (BCD) outputs from the sets of gates 34 through 46 so that only one BCD output is applied to the decoder 50 at a time and so that the right one is applied.

A decoder circuit 58 working in conjunction with the two inputs shown provide four basic signals W, X, Y and 2 that make possible the above-mentioned functions. The decoder 58 simply has two basic input pulse trains, which can, for example, have 1,280 Herz and 640 Herz pulse repetition-rates. Both of these signals are available from divide down circuit 14. These two pulse trains, having a two-to-one frequency relationship, provide four different input states for the decoder 58. The decoder 58, in a simple and known fashion, converts these four input states to four separate outputs W, X, Y and Z on four separate lines. When a signal is present on any of these output lines, the other three signals are absent. Thus when a pulse W is present, there are no X, Y and Z pulses. As a consequence, when a set of LEDs are turned on power is delivered for twenty-five percent of the overall time period during which the display is being actuated.

The duration of each W pulse is equal to the duration of a pulse in the input 1,280 Herz pulse train, i.e., approximately 390 microseconds.

In order to provide the ability to display a date of the month and a seconds indication as well as an hours and minutes display, the four digit display 52 has to be multiplexed between an hours and minutes display and a data and seconds display. This multiplexing is done manually by user actuated demand switches 62 and 64. When the user wishes to view hours-and minutes, he closes the switch 62 thereby opening the gates 66 so that the signals W, X, Y and Z are transmitted through the gate 66 to appear as signals W,, X Y and 2,. When the user wishes to read the date and seconds, he manually closes switch 64 to open the gates 68 and provide the signals W X Y and Z When the gates 66 or 68 are closed, the outputs from these gates are identical to the inputs to these gates.

With the above enabling and switching arrangement in mind, it can be seen that there is a short (390 microsecond) time period display of each of the four digits in sequence with a relatively long (1,160 microseconds) between successive displays of the same digits.

Again, with reference to the units of seconds display, the user will close the switch 64 thereby opening the gates 68. This provides the signal W The signal W is applied to the gates 34 to open the gates 34 for a 390 microsecond time period once each 1,160 microseconds. The BCD signal from the gates 34 is decoded by the decoder 50 to provide a seven segment output which turns on the appropriate segment switches S through S; to connect the appropriate segments of each of the four digits in the display 52 to one side of the battery 54. A the same time the signal W closes the digit switch D to connect all of the segments of the fourth digit to the other side of the battery 54. The result is that for 390 microseconds power is applied to show the appropriate decimal digit indicating the units of seconds in the fourth digit position of the display 52. At the end of this 390 microsecond period, the pulse X opens the gates 36 to providethe appropriate BCD input to the decoder 50 indicating the tens of seconds digit. Because the signal X simultaneously closes the switch D this tens of seconds numeral is represented at the third digit position on the display 52. Thus, in sequence, the four display positions on the display 52 are lit up for 390 microsecond periods each. The same display digit position being lit for 390 microseconds once each 1,160 microseconds.

The Hours Display The handling of the BCD signal representing hours is somewhat special because when it is 10, 11 or 12 oclock, the output from a single set of gates 42 requires that two digit positions on the display 52 be lit in response to a single BCD signal. The arrangement as shown, and to be immediately described, is somewhat complex from a logic point of view and could have been handled in a more straightforward fashion employing a separate set of flip-flops and gates for the representation of the tens of hours position. l-lwever, to handle the hours representation in that fashion would have required an additional flip-flop and thus would have added more to the cost of this device than does the expedient shown in which a few simple gates are employed.

Since the BCD hours output signal from the gates 42 may have to be employed to light up the first and second display digit positions, it is necessary that the outputs from the gates 42 be applied during the time period of both the Y and Z timing signal. Accordingly, the pulses Y and Z are applied through an OR gate to open the gates 42 during both time periods. The decoder 50 responds to the gates 42 output by providing a seven segment output that represents the units of hours decimal digit. During the Y time slot, this unit of hours digit is energized in the second display position of the display unit 52. However, during the Z time slot, it is obviously necessary to prevent this units of hours input from closing any of the segment switches S through 5,. The AND gate 72 is open at that time, because the switch 62 is closed and the 2 output is applied to provide a disabling input to each of the seven AND gate outputs from the decoder 50. The decoder 50, however, has an eighth output on a line that is applied to the AND gate 74. This eighth decoder output is present only when the input to the decoder 50 represents a number ten or greater. Thus, during the Z time slot, if the gates 42 output represents a 10, 1 l or 12 o'- clock time period, the decoder 50 applies an input to the AND gate 74. Since at the same time, the demand switch 62 is closed and the Z input is applied, the AND gate 74 will provide an output which is applied to the switches S and 5:, through OR gates 76. Segment switches S and S are connected to the two segments which provide a numeral 1 display. Since the Z signal turns on first digit switch D the first display position provides a 1 display under the above condition. The Amplifier 12 The oscillator circuit 12 which is employed as an amplifier is one of the major drains of current. The reason for this is that the circuitry involved in this invention preferably employes complementary metal oxide semiconductor devices. The use of such is known in the art to provide minimum current drain. Such devices are current flowing only during the cross-over point when they switch. Thus there is no current drain between switch-over times. Obviously, the higher the frequency applied to such devices, the mroe often will switchover occur and the greater will be the drain. Since the amplifier 12 has to handle the highest frequency signal in this unit, it is the amplifier 12 that has the greatest amount of current drain. The other factor that affects the amount of current used is the voltage. One technique which has been found valuable to achieve one of the major purposes of this invention, that is minimum current drain, is to employ a Zener diode to reduce voltage applied to the oscillator amplifier 12. Circuit B+ voltage (three volts in one embodiment) required for the operation of the display diodes can be cut down to a level (1.8 volts in one embodiment) which permits employment of an amplifier 12 that requires as low an input voltage as is possible. The result is minimized current drain in amplifier 12.

Automatic Intensity Control (FIG. 2)

P16. 2 illustrates the design of the automatic intensity control 56 which is shown as a single block in FIG. 1. With reference to FIG. 2, a standard dual flip-flop unit is employed in conjunction with

various Nand gates

102, 104 and 106 to provide the automatic sequencing that cycles the intensity of the display through three levels. The three intensity levels are a low level of intensity that lasts for at least one second, immediately followed by a one second in duration intermediate level of intensity which in turn is immediately followed by a one second in duration high level of intensity. After the three second display, the display automatically turns off and the

demand display switch

62 or 64 has to be actuated again in order to provide display. In this fashion, the battery drain in the timepiece is kept to a minimum and battery life is extended so that a practical wristwatch is made available.

The dual flip-flop 100 used in this embodiment is a standard type clocked D flip-flop. An example of such a flip-flop is the CD4013 which is sold by the RCA Company and others. The terminals of the dual flipfiop are as indicated, the subscript l representing the first of the two flip-flops and the subscript 2"-representing the second of the two flip-flops. The mutually exclusive outputs of each of the two bi-stable flip-flops are represented as Q and Q. The set inputs which force each flip-flop into the state where its output is high and its Qoutput is low are indicated as S. The re-set inputs, which force ach flip-flop into the state where its Q is high and its output is low are indicated with the symbol R.

The Normal State of the FIG. 2 Arrangement The normal state of the dual flip-flop 100 (that is, the state where the demand display switches 62, 64 are in their normally open position, as shown in FIG. 2) is the re-set state wherein thgoutputs Q, and Q, are low while the outputs Q, and Q, are high. Under this normal state, the two input terminals to the Nand gate 104 are high since these two input terminalsare connected to the Q, and Q output terminals of the dual flip-flop 100. Since both inputs to the Nand gate 104 are high, the output from the Nand gate 104 is low. Thus, since one of the inputs to the Nand gate 102 is low, the output from the Nand gate 102 is high and the l Herz pulse train, that is the other input to the Nand gate 102, does not get through the Nand gate 102.

Since the two inputs Q, and O to the Nand gate 102 are normally low, the output from the Nand gate 106 is high. Thus, in this normal state, the inputs to the two invert circuits ll0 and 112 are high and their outputs are low. Also, the 0 input to Nand gate 111 is high and the other input to Nand gate 110 is high as it is in the normally high output from the flip-flop 140. Thus the output of Nand gate 111 is low. The result is that the transistor T, is biased off (see FIG. 3).

The transistor T, is in series with the cathodes of the LEDs in the display unit 52 and thus, since the transistor T, is off, none of the display unit 52 diodes will be lit.

In Operation In order to view the time, the user closes either the switch 62 or the switch 64. The resulting voltage applied to the set terminal S, forces the first flip-flop into the set state; specifically, the state where the output Q, is high and the output 6, is low. Since the second flipflop is in its re-set state there is no effect f rom applying a voltage to the re-set terminal R With Q, low, the invert circuit 110 goes high and applies an output through the 10,000 ohm resistor R, to the base of thetransistor T, thereby turning on the transistor T,. The magnitude of the resistor R provides a first level of brightness for the cathode displays which, in this case, is the lowest le v el of brightness.

Because the Q, input to the Nand gate 104 has gone low, the Nand gate 104 output goes high and, as a result, the pulse train input ot the Nand gate 102 goes through the Nand gate to be applied as an input to the clock terminal CI, of the first flip-flop. As long as the switch 62 (or 64) is closed, these pulses will have no effect on the first flip-flop because of the signal applied to the set input 5,. However, as soon as the switch 62 (or 64) is released the first flip-flop is released so that the next positive going transistion point in the pulse train at the Cl, terminal will force the first flip-flop from its set state into its re-set state .As a consequence, switching of the output terminal 0, from low to high will apply a pulse input to the clock terminal C1,, of the second flip-flop because of the fact that these two terminals are wired together. The result is to force the second flip-flop from its re-set state into its set state. Under this condition, Q, is high and Q, is low, thus maingining the low output state from the invert circuit 112. Q, is now higl so that the invert circuit output is low. However, 0, is low with the consequence that the output from the Nand gate 111 turns on the transistor T, through the 7,500 ohm resistor R thereby providing a second level of brightness for the display cathodes, which second level of brightness is greater than the first level of brightness provided when the transistor T, was turned on through the 10,000 ohm resistor.

With Q low and Q, high, the Nand gate 104 output remains high and the pulses continue to be applied through the Nand gate 102 to the clock input Cl,. At the next positive going input to the terminal C1,, the first flip-flop is forced from its re-set state to its set state, thereby providing an output from the tgminal Q, and dropping the output from the terminal 0,. At this point, the second flip-flop is not affected because the drop of voltage at the second clock terminal C1 does not cause switching. The result is a state where both inputs to the Nand gate 106 are so that the output from the Nand gate 106 is low and thus the output from the invert circuit 112 is high. This turns on the transistor T, through the diode D which means that a minimum resistance is in series with the display cathodes so that the display cathodes are at their maximum brightness.

The output of Nand gate 104 remains high because both inputs are low. Thus, the next pulse in the l Herz pulse train will get through the Nand gate 102 and the next positive going pulse transition will clock the first flip-flop once more. This will force the first flip-flop from its set state into its re-set st ate thereby causing Q, to go high. The going high of Q, will apply a positive going pulse to the clock terminal CI, of the second flipflop, thereby forcing the second flip-flop from its set state into its re-set state. This returns the F I J. 2 circuit to its normal condition with both 6, and Q high and both Q, and Q low. The result is that the transistor'T, is turned off and the display extinguished. The output of Nand gate 104 is again brought low, disabling Nand gate 102 and thus turning off the l Herz pulse train to Cl,.

Because the one Herz signal through Nand gate 102 causes each of these transitions, the duration of at least the second level of intensity and the third level of intensity is exactly one second each. The duration of the first level of intensity will depend on how long the user holds down the

demand display switch

62 or 64; but the duration of the lowest level ofintensity will be no more than one second after the user releases the

demand display switch

62 or 64.

Time Setting Mechanism (Fig. 3)

One of the advantages of the FIG. 3 embodiment, as will be seen in connection with the discussion below, is that it provides a means for very accurately setting the timepiece.

FIG. 3 Under Normal Timepiece Operating Conditions Under normal timepiece operating conditions (that is, when the time is not being set), the switches are as shown. Specifically, both display demand switches 62 and 64 are open. In addition, there is a set minutes switch 130 and a set hours switch 132, both of which are open. These

switches

130, 132 are closed only when it is desired to set the time.

To understand the operation of setting time, it is best to first understand under normal operations the FIG. 3 circuit. The output of the divide-down circuit (see also FIG. 1) is a pulse train having one pulse per minute. This pulse train is normally applied through the

Nand gates

134, 136 and 138 to be provided as an input to the divide-down circuit 22. The reason, under normal operating conditions, that this pulse train is applied through these three Nand gates is that the second input to the Nand gate 134 is high by virtue of the normal high output on line 160 from the flip-flop circuit 140, the second input to the Nand gate 136 is high by virtue of the normal high output from the flip-flop circuit 142 and the second input to the Nand gate 138 is high by virtue of the high output from the Nand gate 144. The Nand gate 144 has a high output because one of its two inputs is a normally low input from the flip-flop circuit 142. i

In similar fashion, a pulse train from the divide-down circuit 24, which provides a pulse once an hour, is normally applied through the appropriately enabled

Nand gates

146, 148 and 150 to be provided as the input to the divide-down circuit 26. The flip-flop circuit 152 has the same output characteristics as the flip-flop circuit 142 so that the enabling inputs to the

Nand gates

148 and 154 are the same, respectively, as the enabling inputs to the

Nand gates

136 and 144.

Thus it may be seen that when the time is not being set the additional Nand gates between the divide-down

circuits

20 and 22, as well as the additional Nand gates between the divide-down

circuits

24 and 26 do not change the manner in which FIG. 1 functions.

Briefly the reason why the flip-

flop circuits

142 and 152 have the normal output state described above is as follows. With reference to the flip-flop 142, an open display demand switch 62 means that one of the inputs to the Nand gate 1420 is low and thus the output from the Nand gate 142a must be continuously high. With the set minutes switch 130 open, the invert circuit 156 provides a continuously high signal at one of the inputs to the Nand gate 142b. Since the'other input to the Nand gate 142b is the output of the Nand gate 142a, that other input is also high and thus the output of the Nand gate 142b is low. A completely analogous circuit, including a second invert 157, exists with respect to the flip-flop circuit 152. g

The reason why the line 160, which connects an output from the flip-flop 140 to inputs to the

Nandgates

134 and 136 is normally high is described hereinafter in connection with the circuit arrangement at the bottom of FIG. 3. For the purpose of describing the top part of FIG. 3, simply assume that this line 160 is normally high.

It should also be noted that under these normal operating conditions, when the display demand switch 62 is closed, nothing material is affected in the FIG. 3 circuit. Closing the switch 62 will change the corresponding input to the Nand gate 142a from a low to a high. But since the other input to this Nand gate 142 is low, there will be no change in the outputs from the flip-flop 142. The circuit arrangement in connection with the flip-flop circuit 152 is completely analogous.

Setting the Time Now assume that it is desired to set the minutes display ahead. The user of the timepiece depresses the display demand switch 62 so that he can see the time. By itself, this will change nothing. Now the user depresses the set minute switch 130. As soon as he does this, the corresponding input to the Nand gate l42b goes low and the result is that the output of the Nand gate 142b goes high. Since this means that both inputs to the Nand gate 142a are now high, the output of the Nand gate 142a goes low. Thus the outputs of the set-reset flip-flop 142 are switched and the flip-flop 142 can be considered to be in its switched (not normal) state.

An important point should be noted here. If the set minute switch bounces on initial closing, as is frequently the case with hand actuated switches, the flipflop 142 will stay in its switched state because the out put from the Nand gate 142a having gone low will provide at least one low input to the Nand gate 142b and thus assure that the Nand gate 142!) output will remain high. Furthermore, the set minutes switch 130 can be immediately released and the flip-flop l42will remain in its switched state as long as the minutes display demand switch 62 remains depressed. Switch 130 bounce on opening will also not affect the state of the flip-flop 142.

With the outputs of the lfip-flop 142 switched, the enabling signalf for the

Nand gates

136 and 144 are switched from high to low. As a consequence, the Nand gate 136 is disabled (that is, its output will be continually high) and the time signal from the divide-down circuit 20 ceases to progress through the rest of the divide-down circuitry shown in FIG. 1. However, a l Herz signal from gate 16 (see FIG. 1) is applied through the Nand gate 144 and Nand gate 138 to the rest of the divide-down circuitry thereby driving the time record forward 1 minute per second.

If it is desired to set the hours ahead, a completely analogous operation takes place with the display command switch 62 input to the flip-flop circuit 152 and with the set hours switch 132.

Once the desired time has been set, the display demand switch 62 is released and the circuit reverts to its normal state.

With reference to the flip-flop 142, this release of the switch 62 will mean a low corresponding input to and thus a high output from the Nand gate 142. As a consequence, the Nand gate 142b will have a corresponding high input from the output of the Nand gate 142a and since the other input to the Nand gate 142b has gone high because the set minute switch 130 has been released (the set minute switch 130 need not be held longer than necessary to initially switch the flip-flop 142) then the Nand gate 1420 will also switch. This will restore the normal condition for the flip-flop 142. As a consequence, the previous enabling condition of the

ill Nand gates

136 and 144 are re-established and the time signal from the divide-down circuit will proceed to function as normal.

The above description has assumed that the signal on the line 160 has remained high so that the switching back of the flip-flop circuit 142 will re-establish the normal condition. However, in fact the circuitry relating to the flip-flop circuits I40 and 174 modifies this situation for the purpose of permitting very accurate setting of the timepiece. To understand the operation of the circuitry 140, etc. upstream from the line 160, it is helpful to appreciate what the purpose of this circuitry is. The purpose of this circuitry 140, etc. upstream from the line 160 is to permit the user of the timepiece to set the timepiece at a desired point in time somewhat ahead of the real time at which he releases the display demand switch 62 and then to freeze that set time in the timepiece until the display deman switch 62 is further actuated and released so that the user can, on a second release of the display deman switch, synchronize his release with the time standard use.

In order to set the time with the accuracy that is warranted by the circuit of this invention, it is desireable to have this time setting mechanism function so that the user can set the time at some convenient minute or two ahead of the actual time. When so set, the timepiece does not progress any further and when the static display from the timepiece exactly matches the time standard being used, the user depresses an appropriate switch and the timepiece then is switched into its normal dynamic operating state and proceeds to keep time. The lower part of the circuit of FIG. 3 is employed to perform this function.

Again, assuming that it is minutes which are being set, in terms of the user operation, what he does is to press the

switches

62 and 130 as indicated above and allow the time to be set ahead at the rate of one minute per second until he has set the display to a convenient two, or three, as the user desires, minutes ahead of the time which he is using as his standard. He then releases the switch 62 (having already released the switch 130 since it does not have to be closed for more than an instant). If he then depresses the switch 62 once more, the display will hold at the time that he has set and the watch will not be keeping time. When the time he is using as a standard matches the time being displayed, he releases the switch 62 for a second time and now the watch will proceed to keep time correctly. If he then immediately or at some time in the future depresses the switch 62 again in order to read the time he will be reading it correctly.

The way in which this multiple function for the switch 62 is achieved arises out of the ability of the FIG. 3 circuit to affect the state of the line 160. If the output to the point P on the line 160 from the flip-flop circuit 140 is switched from high to low, then the input to the

Nand gates

134 and 164 is low, thereby disabling these Nand gates and preventing the regular time signal from progressing through.

First, it is best to understand the lower part of FIG. 3 during normal time keeping operation. Under such conditions the

switches

62, 130 and 132 are open as shown. The

invert circuits

161, 162 then assure that both inputs to the Nand gate 164 are high so that the Nand gate 164 output is low and thus the invert 166 output is high. This high input to the Nand gate 140a together with a low input to the Nand gate 140!) assures that the flip-flop 140 is in its normal state such that the output P from the Nand gate 14% is high. In order to assure this normal flip-flop 140 state, the rest of the circuitry guarantees that the normal input to the Nand gate 14Gb is low.

Both input X and Y to the Nand gate 168 are high, since these are the high outputs from the flip-

flop circuits

142 and 152, respectively. As a consequence the otuput from the Nand gate 168 is low, the output from the invert circuit 170 is high and, since the other input to the Nand gate 172 is high (since 62 is closed), the output from the Nand gate 172 is low. The flip-flop circuit 174 has the same arrangement as the flip-flop circuit 142. Thus with the input to the Nand gate 174a being low, the input to the Nand gate 174b being high, the output from the Nand gate 174a is high. Because of the invert circuit 176, the second input to the Nand gate 178 is high and thus the output from the Nand gate 178 is low. With this second input to the flip-flop circuit 140 being low, it can be seen that the output on the line 160 is normally high.

It might also be noted that when the switch 62 is closed in order to read the display, the output P on line 160 is not changed once the flip-flop circuit 140 has this normal state. The output from the Nand gate 140a is low and thus the switching of the output from the Nand gate 178 when the switch 62 is closed does not change the fact that there is at least one low input to the Nand gate 140b and thus the fact that the output from the Nand gate l40b will remain high.

During time setting, the switch is normally not depressed for more than a moment and as soon as it is released, the input to the Nand gate switches back to its normally high value. Since the internal input to the Nand gate 140a is low because of the immediately preceding switching of the flip-flop 140, the output from the Nand gate 140a remains high, and thus the internal input to the Nand gate 14% remains high. It is thus essential that the external input to the Nand gate l40b remain high so that the line will remain low. This occurs by virtue of the fact that display switch 62 is held closed so that at least one input to the Nand gate 178 is low and thus the output from the Nand gate 178 is high.

Now, when setting time, not only is the switch 62 held closed, but the switch 130, assuming that it is minutes which is being set, is closed at least momentarily. The closing of the switch 130 causes an input to the Nand gate 164 to become low, its output to become high and thus the input to the Nand gate 140a to become low. This will switch the output of the Nand gate 140a from a low to a high. By itself this is not enough to switch the output from the Nand gate 14Gb. But, it should be noted that the closing of the switch 62 has switched the output of the Nand gate 178 to a high. With the two high inputs to the Nand gate 140b, this output on the line 160 goes low.

As a consequence, the

Nand gates

134 and 146 are disabled during this time setting operation and, as described above, the one I'Ierz pulse train is applied to the divide-down circuit 22.

The release of the switch 62 after the time has been set ahead by the desired two or three minutes does not change the output state of the flip-flop 140. However, it does cause the flip-flop 142 to revert back to its normal condition. As a consequence, both inputs to the Nand gate 168 are high, its output is low and the corresponding input to the Nand gate 172 is again high. But since the switch 62 is open, the other input to the Nand gate 172 is low, and thus the output from the Nand gate 172 is at its normal high state. At this point both external inputs to the flip-flop 174 are high and the output condition of the flip-flop 174 is not changed. This means that the output from the Nand gate 174a remains low and thus guarantees that the output from the Nand gate 178 remains high.

The next closing of the switch 62 does not affect the flip-

flops

142 and 152 which are in their normal state. However, it does apply a second high input to the Nand gate 172 so that the external input to the Nand gate 174a goes low. The result is that the output from the Nand gate 174a goes high. But, at the same time the closing of the switch 62 causes the output of the invert circuit 176 to go low and thus maintains the output of the Nand gate 178 high. Thus the second closing of the switch 62 has not affect on the low state of the line 160.

But now the second releasing of the switch 62 will cause the circuitry to revert back to its normal time keeping state and the line 160 to go high so that the Nand gate 134 is enabled and the regular time keeping signal can proceed from the divide-down circuit to the divide-down circuit 22. The second opening of the switch 62 causes the corresponding input to the Nand gate 172 to go low so that the output from the nand gate 172 goes high. However, this does not affect the fact that the output from the Nand gate 174a is high. But, the opening of the switch 62 does cause the output of the invert circuit 176 to go high so that the output of the Nand gate 178 goes low and the flip-flop circuit 140 switches back to its normal state with the output on the line 160 high.

What is claimed is:

1. In an electronic timepiece, the improvement in a low power drain design comprising in combination:

a matrix of light emitting diodes arranged and multiplexed to provide an N digit display,

first demand switch means to enable said matrix to provide a display of a first N digit item of time information, second demand switch means to enable said matrix to provide a display ofa second N digit item of time information; the type of time information provided by said second demand switch being different from the type of time information provided by said first demand switch, display duration means for automatically disabling said display a predetermined time period after actuation of either of said demand switch means, and

time information signaling means to provide a time information signal as a train of pulses to energize appropriate ones of said light emitting diodes, said train of pulses being applied to said matrix only during said predetermined time period,

said diodes being enabled only in response to the actuation of either of said demand switch means.

2. The improvement of claim 1 wherein N is four.

3. The improvement of claim 2 wherein said first four digit item of time information is hours and minutes and wherein said second four digit item of time information is days and seconds.

4. In an electronic timepiece, the improvement comprising in combination:

a matrix oflight emitting diodes arranged and multiplexed to provide an N digit display,

actuating means to turn on said display to provide a visual indication of the time recorded within the electronic circuitry of said timepiece, said actuating means including at least one display demand 5 switch,

intensity control means responsive to said display demand switch to enable said diodes, said intensity control means including first, second and third loading circuits to determine first, second and third current levels through said light emitting diodes, and

switching means having a normal state, a first state,

a second state and a third state, said switching means when in said normal state disconnecting each of said loading circuits from said diodes, said switching means when in said first, second and third states, respectively, connecting said first, second and third loading circuits to said diodes,

said switching means, when said display demand switch is actuated, being responsive to a predetermined pulse train from said electronic circuitry of said timepiece to switch in sequence from said normal state to said first state, to said second state, to said third state, and to said normal state in response to successive pulses of said predetermined pulse train.

5. The timepiece of claim 4 wherein said predetermined pulse train is a normal timing signal from the time keeping circuitry of the time piece.

6. The timepiece of claim 4 further comprising:

manually actuable time setting switch means for setting the time recorded within the timepiece, and means responsive to the actuation of said time setting switch to disable said switching means and to connect a predetermined one of said first, second and third states to said diodes to provide a constant predetermined display light level during setting.

7. The timepiece of claim 6 wherein said predetermined pulse train is a normal timing signal from the time keeping circuitry of the time piece.

8. The improvement of claim 4 wherein said display demand switch includes:

first and second demand switches, said first and second demand switches being separately actuable,

said first demand switch when actuated enabling Said matrix to provide a display of a first N digit item of time information,

said second demand switch enabling said matrix to 50 provide a display of a second N digit item of time information; the type of time information provided by said second demand switch being different from the type of time information provided by said first demand switch.

9. The improvement of claim 6 wherein said display demand switch includes:

said second demand switch enabling said matrix to provide a display of a second N digit item of time information; the type of time information provided by said second demand switch being different from the type of time information provided by said first demand switch.

10. In an electronic timepiece, the improvement in a low power drain design comprising in combination:

a crystal providing a basic timing signal,

a complementary metal oxide semi-conductor amplifier-oscillator coupled to said crystal to provide an amplified basic timing signal as an N digit display,

a matrix of display diodes to provide direct read-out of the time,

a battery coupled to said display diodes to provide power for said display diodes at battery voltage,

a Zener diode coupled between said amplifier and said battery to provide power for said amplifier at a voltage substantially less than said battery voltage,

whereby the relatively lower voltage at said devices in said amplifier results in substantially less current drain at each cross-over point during switching than the current drain that would occur if battery voltage were employed.

11. The improvement of claim further comprising:

first demand switch means to enable said matrix to provide a display of a first N digit item of time information,

second demand switch means to enable said matrix to provide a display of a second N digit item of time information; the type of time information provided by said second demand switch being different from the type of time information provided by said first demand switch,

display duration means for automatically disabling said display a predetermined time period after actuation of either of said demand switch means, and

12. The improvement of claim 11, further comprising:

intensity control means responsive to said display demand switches to enable said diodes, said intensity control means including first, second and third loading circuits to determine first, second and third current levels through said light emitting diodes, and

switching means having a normal state, a first state, a second state and a third state, said switching means when in said normal state disconnecting each of said loading circuits from said diodes, said switching means when in said first, second and third states, respectively, connecting said first, second and third loading circuits to said diodes,

said switching means, when one of said display demand switches is actuated, being responsive to a predetermined pulse train from said electronic circuitry of said timepiece to switch in sequence from said normal state to said first state, to said second state, to said third state, and to said normal state in response to successive pulses of said predetermined pulse train.

13. The timepiece of claim 12 further comprising:

manually actuable time setting switch means for setting the time recorded within the timepiece, and

means responsive to the actuation of said time setting switch to disable said switching means and to connect a predetermined one of said first, second and third states to said diodes to provide a constant predetermined display light level during setting.

14. In an electronic timepiece having a direct readout display energizable by a battery, the time setting improvement comprising:

a manually actuable time setting switch for setting a predetermined time unit,

a manually actuable display demand switch coupled to the display with the battery to energize the display when actuated,

a first bi-stable switch having a normal re-set state and a set state, said first switch when in said set state coupling a predetermined pulse train to the circuitry controlling said predetermined time unit, said predetermined pulse train having a pulse repetition rate substantially greater than the pulse repetition rate of the time keeping pulse train normally applied to said circuit controlling said predetermined time unit,

a second bi-stable switch having a normal re-set state and a set state,

a third bi-stable switch having a normal re-set state and a set state, said third switch when in said set state disabling the normal time keeping function of the timepiece as to said predetermined time unit,

each of said first, second and third bi-stable switches switchable into its set state in response to the concurrent actuation of said manually actuable switches,

said first bi-stable switch when in said set state, switching into said re-set state in response to the release of said manually actuable switches to disconnect said predetermined pulse train from said circuitry controlling said predetermined time unit,

said second bi-stable switch when in said set state, switching into said re-set state in response to the actuation of said display demand switch when said first bi-stable switch is in said re-set state,

said third bi-stable switch when in said set state,

switching into its re-set state in response to the release of said display demand switch while said second bi-stable switch is in its re-set state,

whereby the closing of said manually operable switches sets said bi-stable switches and causes said predetermined time unit to be set ahead by said predetermined pulse train, the subsequent opening of said manually operable switches causes said time setting to stop without causing the normal time keeping to proceed, the next closing of said display demand switch then re-sets said second bi-stable switch so that the subsequent opening of said display demand switch will re-set said third bi-stable switch and the normal time keeping function will proceed.

15. The improvement of claim 14 wherein said first bi-stable switch when in said set state disables the normal time keeping function of the timepiece as to said predetermined time unit.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTEON Patent No. 3, 765 ,163 Dated October 16, 1973 Inventor(s) Morris Meyer Levine and Arthur F. Cake It is certified that error appears in theabove-identified patent and that said Letters Patent are hereby corrected as shown below:

At Col. 3, line 33, after "are" insert --tWo--;

At Col. 4, line 67, after "any" insert --one--;

At Col. 7, line 22, after "its" insert --Q and line 23, delete "Q" insert --Q--.

Signed and sealed this 19th day of February 197M.

(SEAL) Attest:

EDWA c. MARSHALL DANN w Attesting Officer Commissioner of "Patents ORM PO-1050 (10-69) USCOMM-DC 60376-P69 US. GOVERNMENT PRINTING OFFICE: I969 0-366-334 UNITEb STATES PATENT OFFICE CERTIFICATE 0F @QRRECTEUN Patent No. 3,765,,16'3' Dated October 16, 1973 Inventor (s) V Morris Meyer Levine end Arthur F. Cake It is certified that] error appears in theabove-identified patent and that said Letters Patent are hereby corrected as shown below:

At Col. line 33, after "are" insert "two- At Col. 4, lirie 67, efter "any" insert --'one--; At Col 7, line 22, sfter "'its" insert "Q"; and

line 23, delete "Q'" I insert --Q- Signed and sealed this 19th day of February 197A. L)

(SEAL) Attest: I V Q EDWARD M- RJ c. MARSHALL DANN t n Officer Commissioner of Patents ORM PO-1050 (10-69) USCOMM-DC seen-ps9 i? U.S. GOVERNMENT PRINTING OFFICE I969 0-366-334

Claims

1. In an electronic timepiece, the improvement in a low power drain design comprising in combination: a matrix of light emitting diodes arranged and multiplexed to provide an N digit display, first demand switch means to enable said matrix to provide a display of a first N digit item of time information, second demand switch means to enable said matrix to provide a display of a second N digit item of time information; the type of time information provided by said second demand switch being different from the type of time information provided by sAid first demand switch, display duration means for automatically disabling said display a predetermined time period after actuation of either of said demand switch means, and time information signaling means to provide a time information signal as a train of pulses to energize appropriate ones of said light emitting diodes, said train of pulses being applied to said matrix only during said predetermined time period, said diodes being enabled only in response to the actuation of either of said demand switch means.

2. The improvement of claim 1 wherein N is four.

4. In an electronic timepiece, the improvement comprising in combination: a matrix of light emitting diodes arranged and multiplexed to provide an N digit display, actuating means to turn on said display to provide a visual indication of the time recorded within the electronic circuitry of said timepiece, said actuating means including at least one display demand switch, intensity control means responsive to said display demand switch to enable said diodes, said intensity control means including first, second and third loading circuits to determine first, second and third current levels through said light emitting diodes, and switching means having a normal state, a first state, a second state and a third state, said switching means when in said normal state disconnecting each of said loading circuits from said diodes, said switching means when in said first, second and third states, respectively, connecting said first, second and third loading circuits to said diodes, said switching means, when said display demand switch is actuated, being responsive to a predetermined pulse train from said electronic circuitry of said timepiece to switch in sequence from said normal state to said first state, to said second state, to said third state, and to said normal state in response to successive pulses of said predetermined pulse train.

6. The timepiece of claim 4 further comprising: manually actuable time setting switch means for setting the time recorded within the timepiece, and means responsive to the actuation of said time setting switch to disable said switching means and to connect a predetermined one of said first, second and third states to said diodes to provide a constant predetermined display light level during setting.

8. The improvement of claim 4 wherein said display demand switch includes: first and second demand switches, said first and second demand switches being separately actuable, said first demand switch when actuated enabling said matrix to provide a display of a first N digit item of time information, said second demand switch enabling said matrix to provide a display of a second N digit item of time information; the type of time information provided by said second demand switch being different from the type of time information provided by said first demand switch.

9. The improvement of claim 6 wherein said display demand switch includes: first and second demand switches, said first and second demand switches being separately actuable, said first demand switch when actuated enabling said matrix to provide a display of a first N digit item of time information, said second demand switch enabling said matrix to provide a display of a second N digit item of time information; the type of time information provided by said second demand switch being different from the type of time information provided by said first demand switch. Pg,37

10. In an electronic timepiece, the improvement in a low power drain design comprising in combination: a crystal providing a basic timing signal, a complementary metal oxide semi-conductor amplifier-oscillator coupled to said crystal to provide an amplified basic timing signal as an N digit display, a matrix of display diodes to provide direct read-out of the time, a battery coupled to said display diodes to provide power for said display diodes at battery voltage, a Zener diode coupled between said amplifier and said battery to provide power for said amplifier at a voltage substantially less than said battery voltage, whereby the relatively lower voltage at said devices in said amplifier results in substantially less current drain at each cross-over point during switching than the current drain that would occur if battery voltage were employed.

11. The improvement of claim 10 further comprising: first demand switch means to enable said matrix to provide a display of a first N digit item of time information, second demand switch means to enable said matrix to provide a display of a second N digit item of time information; the type of time information provided by said second demand switch being different from the type of time information provided by said first demand switch, display duration means for automatically disabling said display a predetermined time period after actuation of either of said demand switch means, and time information signaling means to provide a time information signal as a train of pulses to energize appropriate ones of said light emitting diodes, said train of pulses being applied to said matrix only during said predetermined time period, said diodes being enabled only in response to the actuation of either of said demand switch means.

12. The improvement of claim 11, further comprising: intensity control means responsive to said display demand switches to enable said diodes, said intensity control means including first, second and third loading circuits to determine first, second and third current levels through said light emitting diodes, and switching means having a normal state, a first state, a second state and a third state, said switching means when in said normal state disconnecting each of said loading circuits from said diodes, said switching means when in said first, second and third states, respectively, connecting said first, second and third loading circuits to said diodes, said switching means, when one of said display demand switches is actuated, being responsive to a predetermined pulse train from said electronic circuitry of said timepiece to switch in sequence from said normal state to said first state, to said second state, to said third state, and to said normal state in response to successive pulses of said predetermined pulse train.

13. The timepiece of claim 12 further comprising: manually actuable time setting switch means for setting the time recorded within the timepiece, and means responsive to the actuation of said time setting switch to disable said switching means and to connect a predetermined one of said first, second and third states to said diodes to provide a constant predetermined display light level during setting.

14. In an electronic timepiece having a direct read-out display energizable by a battery, the time setting improvement comprising: a manually actuable time setting switch for setting a predetermined time unit, a manually actuable display demand switch coupled to the display with the battery to energize the display when actuated, a first bi-stable switch having a normal re-set state and a set state, said first switch when in said set state coupling a predetermined pulse train to the circuitry controlling said predetermined time unit, said predetermined pulse train having a pulse repetition rate substantially greater than the pulse repetition rate of the time keeping pulse traIn normally applied to said circuit controlling said predetermined time unit, a second bi-stable switch having a normal re-set state and a set state, a third bi-stable switch having a normal re-set state and a set state, said third switch when in said set state disabling the normal time keeping function of the timepiece as to said predetermined time unit, each of said first, second and third bi-stable switches switchable into its set state in response to the concurrent actuation of said manually actuable switches, said first bi-stable switch when in said set state, switching into said re-set state in response to the release of said manually actuable switches to disconnect said predetermined pulse train from said circuitry controlling said predetermined time unit, said second bi-stable switch when in said set state, switching into said re-set state in response to the actuation of said display demand switch when said first bi-stable switch is in said re-set state, said third bi-stable switch when in said set state, switching into its re-set state in response to the release of said display demand switch while said second bi-stable switch is in its re-set state, whereby the closing of said manually operable switches sets said bi-stable switches and causes said predetermined time unit to be set ahead by said predetermined pulse train, the subsequent opening of said manually operable switches causes said time setting to stop without causing the normal time keeping to proceed, the next closing of said display demand switch then re-sets said second bi-stable switch so that the subsequent opening of said display demand switch will re-set said third bi-stable switch and the normal time keeping function will proceed.