US1740330A - Synchronizing clock system - Google Patents

Description

Dec. 17, 1929. J. w. BRYCE ET AL SYNCHRONIZING CLOCK SYSTEM Filed June 23, 1925 Emmi A v n n m w M m My M Q WMHQ M a f W W MEN! R, I] I1. WWW 3K W Patented Dec. 17, 1929 UNITED STATES PATENT orrlcr.

JAMES W. BRYCE, OF BLOOMFIELD, NEW JERSEY, AND CHARLES H. GETZ, OF CLEVE- LAND, OHIO, ASSIGNORS TO INTERNATIONAL TIME RECORDING COMPANY 01' NEW YORK, OF ENDICOTT, NEW YORK, A CORPORATION OF NEW YORK SYNCHRONIZING CLOCK SYSTEM Application filed June 23, 1925. Serial No. 38,954.-

This invention relates to systems for actuating secondary clocks by a master cloclrand to the accomplishment of maintaining all of the clocks in the system in synchronism with the master clock.

The present invention is directed to actuation and synchronization of secondary clocks under the control of a master clock by the agency of electrical energy, and has for its object to utilize for these purposes electrical energy of two different voltages; the higher one of these voltages to be effective during one period of operation and the lower one to be effectiveduring another period of operation.

Another object is to produce an electrically operated clock synchronizing system involving the use of a minimum number of parts and with as few Wires as possible.

Further and other objects of the present invention will be pointed out hereinafter in the accompanying specification and claims and shown in the drawings which by way of illustration show a preferred embodiment of our invention.

In the drawings:

Fig. 1 is a view showing the pertinent parts and wiring of a master clock in cooperative relation to the wiring diagram of a complete system.

Fig. 2 is a view of the minute arbor driving means of the secondary clocks used in the system.

Master clock The master clock in its general details may be of any desired form. For example, it may be that shown in United States Patent No. 1,390,018. Referring to Fig. 1, the master clock includes the usual time train adapted to drive the minute arbor 10 which makes one revolution per hour. The usual verge mechanism 11 is provided. Fixed to the minute shaft are a pair of cams 12, 13, which cams are shaped and positioned to control a pair of contacts 14. Preferably the arrangement of parts is such that the contacts 14 are closed for the synchronizing period and opened at other times. It will be obvious, however, that by a proper rearrangement of the associated parts of the system these cam contacts could operate in a reverse manner opening in the synchronizing period and closing at other times.

In the present and preferred embodiment we provide for a synchronizing period commencing just after the minute hand of the master clock is forty-four minutes after the hour and terminating ust prior to thesixtieth minute, for reasons which will hereinafter appear.

Also fixed to the minute arbor 10 is a cam 15 which is adapted to control the opening and closing of a contact 16. In the preferred embodiment contact 16 is arranged to close just after the fifty-ninth minute position and open at approximately fifty-nine and a half. For a proper functioning of the apparatus the contacts 16 should open just before contacts 14 open at the end of the synchronizing period.

In addition, the master clock is provided with the usual minute impulse contacts 17 which are controlled in the usual way from a a minute cam 18 or otherwise as is the custom in clocks of this sort.

For advancing or stepping forward the secondaries we provide quick acting contacts 19 and preferably operate these contacts by attaching one of them to the verge mechanism 11. These contacts 19 will close at every swing of the pendulum if a pendulum movement is employed.

The contacts may be mounted on the master clock according to well known means, as for example, similarly to those disclosed in the United States application Serial No. 722,439, filed June 26, 1924.

Secondary clock The secondary clock shown in Fig. 2 is of conventional form and it includes a minute arbor shaft 20 which makes one revolution per hour. This shaft is preferably advanced by means of an impulse magnet 21 which acts through the usual ratchet wheel 22 to advance the minute arbor 20 step by step each time the magnet 21 receives an impulse from the master clock. Carried by the minute arbor 20 on each secondary clock we provide a synchronizing cam 23. Cooperating with this cam is a contact device of any desired form here shown as including a blade 24 adapted to close contacts 25 when the raised portion of the cam is under the blade 24 and to close contacts 26 when the blade 24 is on the low portions of the cam. The cam 23 is so timed that when the minute hand of the clock is opposite the fifty-ninth minute the blade 24 has just fallen off the high point 27 of the cam 23 breaking contact 25 and making con tact 26. The cam rise 28 in the present embodimentof the invention is disposed substantially 180 around the cam from the dropofi point 27 so that at twenty-nine minutes after the hour or slightly thereafter contacts 25 are closed and contacts 26 will be opened. The parts are so arranged that at no time except momentarily during the shifting of blade 24 are both contacts 25 and 26 open.

Referring to the circuit diagram, current is supplied to the system from a battery, one end of which is grounded, the other end having connections to the master clock and to the secondary clocks through a lead 30. Another lead 31 is connected to the battery so as to include a fewer number of cells in circuit. It is evident that lead 30 is under a higher voltage than lead 31 and the determination of whether a high or low voltage is to be i1npressed across the secondary clocks is dependent u on the position of switch 29, which position ears a definite time relation to the master clock as will be hereinafter pointed out.

It is apparent that either direct current or alternating current can be used to operate this system and an auto-transformer connected to an alternating source of current, not shown, is illustrated. In this illustration, lead 30 is the high tension line and lead 31 is the low tension line corresponding with leads 30 and 31 respectively, of the direct current system.

In the present system, one end of the source of electrical energy is grounded at C at all times, and the so-called C circuit forms a common return for the secondary clocks which may be metallic, if desired, which is ordinarily the case in clock systems of this class. For simplicity in the present description a ground return for the master and secondary clocks is utilized.

Normal operation The first operation to be described will be the normal minute impulse operation for controlling the secondary clocks. For clarity it will be assumed that all of the clocks at this moment are at a position somewhere between the hour reading and forty-four minutes later.

The circuits of the master clock always remain across the high voltage line, and current is taken from the battery over wires 32, 33 and 34, through minute contacts 17, wire 35,

' timed to close.

master relay coil 36, wire 37, and back through the ground to the battery. This periodic flow of current energizes the master relay coil 36 once per minute attracting relay armature 38 and causing the current to flow from the high voltage line 30 through switch 29, line A, arn'iature 38, feed line 39, either contact 25 or contact 26, arm 24 and to the clock impulse magnet coil 21 and back through the common ground return C to the battery. Thus each minute the secondary clocks are advanced in step with the master clock.

The high voltage available during this period enables the secondary clocks to be actuated without interruption no matter which of contacts 25 or'26 is closed. Vhen contact 25 is closed, current is taken from feed line 39 through branch line 40, and when contact 26 is closed current is taken from feed line 39 through a resistance 41. In either case, the strength of the current is sufficient to operate magnets 21.

Synchronization The synchronizing period starts just after the forty-fourth minute when contacts 14 are This causes current to flow from high voltage line 30, through wires 32, 33, 42 and contacts 14 now closed, synchronizing relay coil 44 and back to the battery. The 9 energization of synchronizing relay coil 44 attracts the armature of switch 29 thereby throwing the secondary clock circuit over to the low voltage line 31. This position of switch 29 is maintained until just prior to the sixtieth minute by reason of the continued energization of coil 44. During this period the secondary clocks which are on time or slow are advanced step by step on each minute by the minute impulses of magnet coil 21 caused by the impulse of current from the low voltage line 31 through line A, armature 38, line 39, branch 40, contact 25, magnet coil 21, and ground C. The secondary clocks that were fast will have stopped at the hour position, for in these clocks contacts 25 will have opened and resistance 41 will have been thrown into the circuit by the closing of contact 26. Resistance 41 is designed to cut down the current flowing under the low voltage impression to such an extent as not to be effective to operate electromagnet 21.

Hence, between the sixtieth and fortyfourth minute as indicated by the master clock when the high voltage lines are connected with the secondary clocks, current will flow through the secondary clocks of suflicient strength to energize magnet coil 21 on each minute impulse, whichever one of contacts 25 and 26 is closed. However, during the synchronizing period starting just after the forty-fourth minute only the secondary clocks having contacts 25 closed will be actuated by the minute and acceleration impulses hereinafter described. Those having contacts 26 lit closed will stop because the current will not be of sufiicient strength to actuate the coil magnets 21. f

In the diagram three secondary clocks are shown marked respectively X, Y and Z. Clock X is assumed to be on time with its minute hand in agreement with the master clock. Clock-Y is assumed to be fifteen minutes fast and clock Z fifteen minutes slow. Synchronizing cam 28 of clock X is about the center of its high portion thus closing contacts 2'5. Cam 23 of the Y or fast clock has reached such position that blade 24 has dropped off step 27 closing contacts 26 and opening contacts 25. Cam 23 of the Z or slow clock has just passed the rise and has reclosed contacts 25 and has opened contacts 26.

For the reasons previously explained, during the period of synchronization, impulses of sufficient strength to energize magnet coil 21 can be delivered to a secondary clock only when branch 40 is in its circuit and this only occurs when contact 25 is closed. Clock Y will therefore remain stationary until the end of the synchronizing period. Clocks X and Z, on the other hand, are in such position that contacts 25 are closed and they therefore are in condition to receive minute impulses during the synchronizing period. The clocks X and Z then step along in the usual way,

receiving the normal impulses every minute until the end of the synchronizing period is reached.

Just after the fifty-ninth minute, as indicated by the master clock, the cam 15 reaches a position to close the contacts 16. Current now flows from the source 30 over wire 32,

-wire 46, contacts 16, wire 47, contacts 19 to wire 35 and master relay coil 36, wire 37, and back to the source. The contacts 19 close in comparatively rapid succession, for example, once every two seconds and energize coil 36 a plurality of times which attracts armature 38 a plurality of times thereby sending a succession of fast or acceleration impulses over wire A. It will be understood that on clock X which is on time, contacts 25 will have opened just after the fifty-ninth impulse and before contacts 16 were closed, thereby preventing the fast step-up impulses from effecting it. Clock Z. on the other hand, will have the parts in such position that contacts 25 are closed so that the fast impulses are received by it which causes the clock to be stepped forward or accelerated to advance the synchronizing cam until it reaches a position to open contacts 25. All of the clocks X, Y and Z are now in synchronism with the master clock. After contacts 19 have sent the .selected number of fast impulses, contacts 16 will open thus rendering contacts 19 ineffective to send further impulses. Shortly after contacts 16 open and just before the sixtieth minute impulse, contacts 14 will open thus (file-energizing the synchronizing relay coil 44, releasing the armature of switch 29 and allowing the switch to throw the secondary clock -Would be behind time a greater number of minutes than there are acceleration impulses furnished by the master clock, it would still be late at the hour impulse and contacts 25 would not have opened. This clock would still continue to operate, however. On the next hour this delinquent clock would be brought into synchronism with the others, as already described. The timing of the various cams in the system disclosed herein has been found satisfactory to maintain all clocks in synchronism and it is only under unusual circumstances that any secondary clock would be so slow as not to be on time on the sixtieth minute.

It will be understood that if in any case it is required to correct the time of the entire system, as for example, when the master clock is running fast or slow and this correction is to be within the range permitted by the synchronizing period it is only necessary to re set the hands of the master clock to the desired extent. The secondaries will then set themselves within the next hour. If the amount is in excess of the synchronizing period for which the system is designed, for example, when a daylight saving correction is required, a manual control is brought into operation as shown in Fig. 1 which will now be described. Referring to the diagram a wire 48 is provided tcrl'ninating in a switch point as shown. A switch mom )6! 49 is disposed in line 32 and for the usual running position is closed in the position shown. To retard the secondary clocks the switch 49 is displaced to the open or off position breaking line 32 and also being out of contact with the switch point on wire 48. This switch is maintained open for the desired retarding period. If it is desired to advance the clock the switch 49 is thrown to connect with the switch point or wire 48. The effect of connecting switch 49 with wire 48 is to cause the fast set-up contacts 19 to come into action and rapidly advance the various secondary clocks. The switch 49 will be held closed until the secondary clocks advance to the desired extent. For example, to advance all of the clocks one hour with contacts 19 closing every two seconds it will take two minutes to bring about the proper advance of the secondaries.

It will be understood that it is not essential to hold switch 49 closed for the exact period inasmuch as the synchronizing system will function to bring the clocks in time with the master clock whether the said secondary clocks are fast or slow with respect to the master clock. It is only necessary that they be brought within the range of the synchronizing period.

The above is equally true with regard to retarding operations it being only necessary to open switch 49 for approximately the desired retarding period.

While in the present embodiment we have selected a synchronizing period of fifteen minutes, it will be understood that this period is given merely for purposes of illustration and that this period may be greater or less as desired. In convei'itional clock systems of the present day this period has been found to be ample for all practical purposes.

In the present system it will be apparent that the master clock sends out over a circuit normal impulses impressed under high voltage for a definite period and then automatically shuts off the high voltage source of current and connects a low voltage source of current across the same circuit for another period of time which corresponds to the synchronizing period and during which normal and fast impulses are sent out. All of the apparatus necessary to produce this operation is self-contained in the master clock.

T he actuation and synchronization of the secondary clocks are dependent upon the strength of current received by them and their own chronologic condition determines the utilization of the currents. The devices for governing their operation are self-contained in the secondary clocks, and each clock determines whether it shall receive normal impulses, fast impulses, or whether it shall be connected so as not to receive any impulses for a time.

Certain broad features of the present invention are broadly claimed in the copending application of James WV. Bryce, Serial No. 21.322, fiicd April 20, 1925.

What we claim is:

1. In a synchronizing clock system, the combination of a master clock, means for controlling the distribution of electrical energy under different differences of potential over a common circuit, a secondary clock connected across said common circuit each secondary clock having a translating device, and means responsive to a difference in potential for determining Whether the electrical energy from said common circuit will be utilized for advancing the secondary clock.

2. In a synchronizing clock system, the combination of a master clock, means for controlling the distribution of electrical energy under different differences of potential over a common circuit, means actuated by said clock for controlling periodic excitation of said common circuit, a secondary clock connected across said common circuit each secondary clock having a translating device for actuating the same, and means responsive to a difference in potential controlled by said translating device to determine whether or not said secondary clock will be actuated by impulses caused by said periodic excitation of said common circuit.

3. In a synchronizing clock system, the combination of a master clock, a main circuit, means for sending out over said main circuit a series of normal and rapid impulses periodically, a source of current having high potential difference, a second source of current having low potential difference, means to de termine which of said two sources will supply the current for said impulses, and means in the master clock to time and select the sending of the impulses so that at least one impulse of higher potential difference is sent out by the master clock immediately following the sending of the rapid impulses which impulses are of the lower potential difference.

4. In a synchronizing clock system, the combination of a master clock, a main circuit, means for sending out over said main circuit a series of normal and rapid impulses periodically, a source of current having high potential difference, a second source of current having low potential difference, and means controlled by the clock for determining which of said sources of current will excite said main circuit, said last mentioned means having associated with it means for causing at least one impulse of higher potential difference to be emitted as a normal impulse immediately following the emission of the rapid impulses, which rapid impulses are emitted with a relatively lower potential difierence.

5. In a synchronizing clock system, the combination of a master clock, means controlling the distribution of electrical energy of different voltages, a secondary clock, a circuit for conducting said electrical energy to said secondary clock, means interposed in said circuit for reducing the strength of the current flowing therethrough, and means controlled by the chronologic condition of said secondary clock for changing the relation of said means.

6. In a synchronizing clock system, the combination of a master clock, two sources of current under different differences of potential, a secondary clock, a secondary clock circuit electrically related to said master clock, means controlled by said master clock for connecting either one of said sources of our rent with said secondary clock circuit, two branch lines in said secondary clock, a resistance in one of said branches, and a switch for connectin either one of said branch lines in said secon ary clockcircuit.

7. In a secondary clock, the combination of a shaft, a ratchet wheel on said shaft, an electromagnet for actuating said ratchet wheel, two branch lines, a resistance in one of said lines, a switch, and means controlled by the position of said shaft for connecting either one of said lines in series with the electromagnet.

8. In a secondary clock, the combination of electromagnetic actuating means, and means including an electrical resistance for selectively controlling the operation and nonoperation of said actuating means.

9. In a secondary clock, the combination of electromagnetic actuating means for the clock hands, a resistance, a switch, and means controlled by the chronologic position of said clock hands for putting said resistance into or. out of circuit with said electromagnetic means.

10. In a secondary clock, the combination comprising a main circuit for supplying electrical energy, an electromagnetic actuating means in said main circuit normally operable, two branch lines, one of said branch lines having more electrical resistance thanthe other, and means for connecting one or the other of said branch lines in series with said electromagnetic means.

11. In a synchronizing clock system, the combination of a master clock, a main circuit, a secondary clock, means controlled by said master clock for controlling the distribution of electrical energy over said main circuit, two sources of electrical energy having different differences in potential, means for selecting from which one of the two of said sources energy shall be derived, translating means for actuating said secondary clock, and means for determining whether the electrical energy from said main circuit will be utilized for advancing said secondary clock. I

12. In a synchronizing clock system, the combination of a master clock, a main circuit, means controlling the distribution of electrical energy over said main circuit, a secondary clock, translating means in said main circuit for actuating said secondary clock, branch lines of said main circuit, one of said branch lines having more electrical resistance than the other, and means for connecting one or the other of said branch lines in said main circuit.

13. In a synchronizing clock system, the combination of a master clock, a main circuit, a secondary clock, means for energizing said main circuit by impulses at a normal rate and at a faster than normal rate, two sources of electrical energy having different differences in potential, means for determining from which one of the two of said sources of electrical energy shall be derived electrical energy for said impulses, electromagnetic means for actuating said secondary clock,"

two branch lines in said main circuit, and means for connecting one or the other of said branch lines in circuit with said electromagnetic means.

14. A secondary clock adapted to receive impulses of current over a single line of different voltage characteristics at different times, an actuating magnet for actuating the clock step-by-step, and means for suppressing the operation thereof upon the concurrence of the reception by the clock of impulses of a given voltage with a certain chronological setting of the clock itself. 15. The invention set forth in claim 14 in which means is provided for reinitiating the impulse advance of the clock upon the reception of an impulse of current of different voltage after the operation of the magnet has been suppressed as a result of the ineffectual effort of current impulses of other voltage.

16. A master clock for use in a synchronized clock system with provisions for sending out over a line normal impulses and for sending rapid impulses for a particular time period in combination with means in the master clock forcausing the normal current impulses to be sent out with a particular voltage characteristic, and means in said master clock for causing impulses of a different voltage characteristic to be sent out during the said rapid impulse sending period.

17. A synchronized clock system including a single line circuit, a master clock with provisions for sending normal impulses and fast impulses over said single line, a secondary clock also connected to said line, and means for effecting synchronization of the master and secondary clocks, said means comprising,

.in combination, means in the master clock for varying the "oltage of the normal impulses with respect to the voltage of the fast impulses, and means in the secondary clock for selectively controlling the operation thereof both in accordance with the chronological condition of the secondary clock and in accordance with the voltage character of the impulses being sent over the line.

18. In a synchronized clock system with a master clock with provisions for sending normal and rapid impulses, a line circuit, and a secondary clock with an operating magnet therein, in combination with means at the master clock for sending impulses of variable voltage characteristics at variable time periods, means in the secondary clock for coordinating the operating magnet of the clock for operation or non-operation in accordance with the conjoint control of the character of voltage of the impulses which are being then sent out by the master clock and in further accordance with the chronological condition of the secondary clock.

19. The invention set forth in claim 18 in -which means is provided at the secondary clock for reestablishing an operating condition of the magnet after the magnet operation has been suppressed, said means being in condition for operation upon initial receipt of a current'impulse of different voltage after the receipt of impulses of current of ineffective voltages.

20. A secondary clock comprising in combination, time indicating means, electromagnetically actuated means for causing step by step advance of said time indicating means, an electrical resistance device, and means controlled by the chronological condition of the clock itself for causing said resistance device to suspend advancement of said time indicating means unless and until the energizing electromotive force received by the clock is increased.

21. A secondary clock comprising in combination, time indicating means, electromagnetically actuated means including an impulse magnet for causing step by step advance of said time indicating means, an electrical resistance device, and means controlled by he chronological condition of the clock itself for rendering said resistance device effective to prevent sufficient current to flow through the electromagnet of said impulse actuating means to advance the clock unless and until increased voltage is received by the clock.

22. A synchronized clock system comprising in combination a master clock and a secondary clock, the latter being of an impulse type and comprising a common impulse magnet which by its own action effects all advancing movements of the clock which are required for normal step by step advance or for accelerating the clock if the same is slow and master clock controlled means for sending out impulses of varying voltage, and selecting means at the secondary clock for rendering effective or ineffective the received impulses for driving the secondary clock.

23. A synchronized clock system having a master clock and a secondary clock of the impulse type and a single line circuit connect- 1ng the same for operating and synchronizing the clocks and comprising in combination a common impulse magnet which is employed in the secondary clock for both advancing the clock for normal step by step operations and for accelerating it by step by step operations when it is slow, and supplemental devices which are provided in the secondary clock for permitting the passage of effective impulses to the impulse magnet or for rendering ineffective impulses flowing to the magnet, said devices exerting control conjointly in accordance with the voltage of the impulses and in accordance with the chrono-" lo ical condition of the secondary clock for e ecting synchronization of the secondary clock with respect to the master clock and for permitting the advance of the secondary clock in synchronization with the master clock.

24. A synchronized clock system including a master clock and secondary clocks of the impulse type, each of the latter having a single impulse magnet which effects all step by step advance of the clock both for normal step by step advance and also for accelerating step by step advance when a clock is slow, and including in combination, a common line circuit connecting the master and secondary clocks, means at the master clock for sending out over the same common line circuit all the controlling impulses to the clocks which comprise a number of relatii ely low voltage regular impulses, more rapidly recurring accelerating and relatively low voltage impulses and at a certain starting time as determined by the master clock one or more impulses of relatively higher voltage for reinitiating advance of the clocks, and means at each secondary clock including a resistance and switching device which latter device is controlled by the chronological condition of the associated secondary clock for suspending advance of the clock by rendering the low voltage impulses which are received ineffective to operate the impulse magnet and for also permitting a reinitiated impulse advance of the clock upon the reception of the higher voltage impulses from the master clock.

25. A synchronized clock system including a master clock and at least one secondary clock of the impulse type, each secondary clock having a common impulse magnet for advancing the clock for normal step by step advance and for accelerating the clock by step by step operations when it is slow, and including in combination, a single line circuit connecting the master and secondary clocks, each secondary clock including a resistance and switching means for effecting suspension of further step by step advance of the secondary clock, said switching means being controlled by the chronological condition of the secondary clock itself, and said resistance being adapted under the control of the switching means to prevent effective energization of the secondary clock impulse magnet When impulses are received of a determined voltage from the master clock and when operation of the secondary clock is to be suspended, and means in the master clock including provisions for sending out over the same common line circuit a reinitiating impulse of relatively higher voltage than those previously sent to again cause effective energization of the impulse magnet through the cooperating resistance.

26. A synchronized clock system wherein the system comprises a master clock and one or more secondary clocks, each secondary clock being of the impulse type and including an impulse magnet which effects all step by III step advance of the clock whether for normal step by step operations or for rapid step by step accelerating operations when the clock is slow, and comprising in combination a single line circuit which includes an outgoing line and return line extending from the master clock to the secondary clocks, each of the secondary clocks being connected in parallel relation to each other and each being connected respectively to the outgoing and return line, means at the master clock for sending out over the common line circuit current impulses of a certain voltage for a number of normal impulses and for the fast stepping up impulses and for also sending out subsequently over the same common line circuit at least one impulse of a higher voltage at a certain time as determined by the chronological condition of the master clock, and cooperating means at each secondary clock comprising a switching means and a resistance means adapted for cooperation with the impulse magnet, the switching means being controlled by the chronological condition of the secondary clock, said switching means and resistance being adapted to suspend operation of each secondary clock when said secondary clock attains a certain time condition andwhile low voltage impulses are being received over the line circuit and for permitting reinitiated advance of the clock upon the reception of a higher voltage impulse over the same line circuit.

27. A synchronized clock system including a master clock, a secondary clock, said secondary clock including an impulse magnet which efi'ects all step by step advance of the clock including the normal advance and the rapid step by step impulse advance for accelerating the clock, and including in combination, a single line circuit connecting the master and secondary clock, means at the master clock for sending out all over the same common line circuit a number of relatively low voltage impulses and also a number of more rapidly recurring relatively low voltage impulses for accelerating the secondary clock if slow, and also including means at said master clock for sending out over the same common line circuit beginning from a certain starting time as determined by the chronological condition of the clock and which time is subsequent to the sending out of the low voltage impulses certain impulses of relatively higher voltage for reinitiating impulse advance of the secondary clock after its operation has been suspended, and cooperating means at the secondary clock adapted to receive over the same common line circuit from the master clock the low voltage impulses both rapid and slow and the high voltage impulses, said means including a resistance and switching means cooperating with the impulse magnet in the secondary clock with provisions for interrupting the step by step advance of the secondary clock at a certain time as determined by the chronological condition of the clock and while low voltage impulses are being received, and for permitting a reinitiated step by step advance after suspension of operation of the secondary clock and upon reception of the high voltage impulses from the master clock.

28. A synchronized clock system including a master clock anda secondary clock including in combination, means for sending out from the master clock to the secondary clock a series of impulses of one voltage and also impulses of a difi'erent voltage, means in the secondary clock comprising an impulse magnet responsive to said impulses for causing all advancing movement of the secondary clock, and means controlled by the chronological condition of the secondary clock and also responsive to a difference in voltage of the received impulses for rendering the impulses of one voltage effective or inefi'ective to advance the secondary clock by said impulse magnet.

29. A nized clock systems and comprising a common impulse magnet which by its own action cffcets all advancing movements of the clock which are required for normal step by step advance or for accelerating the clock if the same is slow, with means at each secondary clock for suspending its advance under certain chronological conditions of the clock, said means comprising means for rendering received impulses ineffective, said means being also variably effected by a received impulse of higher voltage to permit a reinitiated advance of the clock under the action of the impulse magnet after its action has been suspended, and means including a single line circuit extending into the secondary clock from the master clock for sending thereinto from the master clock both the normal and fast impulses which normally advance and accelerate the clock and for also transmitting thereto a current impulse of special voltage characteristics which upon its reception by the clock is adapted to reinitiate an advance thereof after its operation has been suspended.

30. A synchronized clock system including a master clock and a secondary clock of the impulse type and a single line circuit connecting the same for operating and synchronizing the clock and comprising in combination a common impulse magnet which is employed in the secondary clock for both advancing the clock for normal step by step operations and for accelerating for step by step operations when it is slow and supplemental selecting devices which are provided in the secondary clock for suspending operation of the secondary clock and which devices are responsive to current of. special voltage characteristics which is sent by the master clock to secondary clock for use in synchrothe secondary clock over the common line circuit which transmits the normal and :fast impulses for rendering the impulse magnet again efiective for o eration to advance the clock when the secon ary clock is to reinitiate its advance in synchronism with the master clock.

31. A secondary clock comprising in combination time indicating means and step by step mechanism for operating the same, an electromagnet which operates and causes the step by step mechanism to advance the indicating means at a normal rate when the time indication is correct and at a rapid rate when the time indication is slow, means including a resistance and a switching means, the latter being operated by the step by step mechanism when the time indicating means has reached a predetermined position for suspending operation for the step by step mechanism by the electromagnet, and means responsive to concurrent energization of said resistance device and electromagnet by current of a voltage characteristic different from that of the current which caused the time indicating means to be brought up to said predetermined position for causing the electromagnet again to advance the time indicating means.

In testimony whereof we hereto aflix our signatures.

JAMES W. BRYCE. CHARLES H. GETZ.

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