AU701124B2 - Synchronization of a timepiece to a reference time - Google Patents

Description

r a P/00/011 Regulation 3.2

AUSTRALIA

Patents Act 1990

ORIGINAL

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COMPLETE SPECIFICATION STANDARD PATENT Invention Title: SYNCHRONIZATION OF A TIMEPIECE TO A REFERENCE TIME

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i:r The following statement is a full description of this invention, including the best method of performing it known to us:-

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I 2 This invention relates to the synchronization of a timepiece to a reference time, and in particular, relates to a method and apparatus for synchronizing a timepiece to such a time.

In this specification, the term "timepiece" refers to a horological device for keeping and/or displaying time, and/or for generating a signal which in turn may result in a display of time.

Timekeeping devices have been in use for some 3,500 years. Mechanical timepieces have been in existence for 900 years, and clocks have been known since the fourteenth century.

Every location on a particular degree of longitude has the same local time, and it follows that such a location has a slightly different time from that in a town or village a few kilometres to the east or west. In the days before improved communications and transport, such places were isolated, and there was no need to impose any time standard. With the coming of the railways, and S 15 subsequently the telegraph, it became both necessary and possible to impose a single standard time for an entire country (such as the United Kingdom) or for each of a number of time zones extending across a country (such as the United States of America and Australia).

Australia is divided into three time zones: Eastern Standard Time [EST] (Queensland, New South Wales, the Australian Capital Territory, Victoria and •Tasmania), Central Standard Time [CST] (South Australia and the Northern Territory) and Western Standard Time [WST] (Western Australia). Some States have adopted Daylight Saving, advancing clocks one hour ahead of the relevant Standard time for a period of some months between spring and autumn each d 25 year. Others have not, which results in there being up to five time zones in Australia during the period in which Daylight Saving operates. In the spring to autumn period of 1994/1995, a different set of five time zones was created by the decisions of New South Wales and Victoria to return to Eastern Standard Time on different dates. This has created difficulties for persons, particularly ir

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r i business persons, in those States, which are normally in the one time zone.

Despite the problems caused by having between three and five time zones, and the twice-yearly change of the time regime in all but three of the eight States and Territories, most timepieces in Australia operate independently of each other, and require a manual operation to correct and change the time displayed, and day and date when applicable.

In Australia, Telstra Corporation is responsible for providing reference times, producing the "pips" heard on the hour (on the half-hour in South Australia and the Northern Territory) on some radio stations, providing the dial-up "speaking clock", and providing equivalent facilities for computer users via modems.

Telstra Corporation also has a representative on the National Time Committee, although as has been mentioned earlier in this specification, the States have powers over such things as whether or not a particular State adopts Daylight Saving, and the entry and exit dates to and from Daylight Saving.

There are in existence in Australia installations of a plurality of clocks, operating on a "master-slave" basis, where a master clock is connected by electrical cabling to a number of slave clocks, which are controlled by the master clock and as a result all show the same time. Such installations may be found in locations such as hospitals and airport terminals. They are cumbersome, and expensive to construct, and are only useful where no slave clock is very far from the master clock.

The concept of using a radio signal to carry time information was first published some forty years ago. In US-A-4,204,398 by Lemelson, published on 27 May 1980, there is disclosed a method and apparatus for automatically setting timepieces in a time zone. The method involved the setting of a timepiece such as a watch worn by a traveller passing from one time zone to another by the transmission of a time-related signal, which results in the timepiece displaying or being able to display,;:he correct time for the time zone in which the timepiece is located.

4 AU-A-83677/91 by NEC Corporation, published on 12 March 1992, relates to time-keeping apparatus which utilises a cellular mobile communications system as a source of transmitted signals which cause a correct time to be displayed on a timepiece which is adapted to be mounted on a vehicle or to be personally carried.

The Federal Republic of Germany has in operation a system called the German Radio Clock, the operation of which is described in AU-A-59372/94. A powerful VLF transmitter broadcasts signals which are received by a large number of clocks throughout Europe (much of which operates on Central European Time), 10 and which synchronizes those clocks, bringing each of them to the correct time.

4 p There is clearly a need for a system in Australia which is able to remotely Ssynchronize and reset timepieces. For example, it is essential to be able to maintain thp correct time on timepieces most of which have digital displays Swhich are associated with personal computers, cash registers, fax machines, 15 automated teller machines (ATMs), debit and credit card terminals, and so on.

9 This is particularly so for accurate records of such things as credit card :transactions, ATM transactions, faxes sent and received, and so on, as well as dealing with the problems caused by Daylight Saving changes. Many of the a present clocks used in such applications drift alarmingly over relatively short periods of time. In addition, there is rarely any structure in place to check and correct the time shown on such a timepiece; it is also quite common for such clocks to not be reset for and/or after Daylight Saving changes. There is clearly a need for a system for automatically setting a timepiece to the correct time.

It is an object of this invention to provide an improved method and an improved apparatus for the synchronization of timepieces.

The invention provides apparatus for synchronizing a timepiece to a reference time, including: means to receive and decode a transmitted signal, said signal including 4o 1 information relating to said reference time; means to extract from the decoded signal information relating to the correct time for a preset time zone, locality or offset; means to display or to output said correct time; and means adapted to store daylight saving change information included in said signal, in advance of the date and time specified for a change to or from daylight saving time, so that in the absence of a specific signal transmission to initiate a daylight saving change, a time correction can still be made on the date and at the time specified for said change.

i The invention also provides a method of synchronizing a timepiece to a reference time, including the steps of: generating a signal which includes information relating to said reference time, and information relating to the date and time of a change to or from daylight saving time; 15 transmitting said signal from a transmitter in advance of said date and time of said change to or from daylight saving time; receiving and decoding said signal at or in the vicinity of said timepiece; processing said signal to enable said timepiece to display a time, or generate an output representative of said time, said time being the correct time for a preset zone, locality or offset; extracting from the decoded signal information relating to the correct time for a preset time zone, locality or offset; displayinfgor outputting said correct time; and 4 f%4 6 storing said information on the date and time of a change to or from daylight saving time, included in said signal, so that even in the absence of a specific signal transmission to initiate a daylight saving change, a time correction can still be made on the date and at the time specified for said change.

The invention further provides a method of setting a timepiece in accordance with a signal containing data on a daylight saving time change, including: transmitting said signal in advance of the date and time of said daylight saving time change contained in said data; 10 receiving said signal at or in the vicinity of a timepiece; I decoding said signal; storing said data; and I: setting, at said date and contained in said data, said timepiece to daylight saving time.

I0 15 The invention also provides a timepiece adapted to receive and decode a signal ontaining time zone data for a number of time zones, and data on a daylight saving change, including: means to store said data on a daylight saving change in advance of the predetermined date and time of said change so that the time alteration consequent upon said changes may be effected for that timepiece on said predetermined time and date, even if no further specific signal transmission to initiate a daylight saving change is received.

Embodiments of the invention, which may be preferred, will be described in detail hereinafter with reference to the accompanying drawings, in which: 7 Fig 1. is a block diagram of one embodiment of the method and apparatus of the invention; Fig 2. is a block diagram of the signal generation and transmission aspect of the embodiment of Fig. 1; and Fig. 3 is a circuit diagram of one embodiment of receiving/decoding apparatus.

The block diagram of Fig. 1 represents a preferred embodiment of the present invention, which embodiment utilises a Radio Paging Network (RPN). The RPN is adapted to send messages to paging devices carried by persons. ,*-'hough at 10 the present time RPNs do not service the entire area of Australia, they can reach some 90% of the population, and operators are committed to an expansion of their networks. A RPN network is currently operated by sending signals by landlines to master transmitters, which relay signals to a larger number of slave transmitters. In the future, signals may be transmitted from an Earth station to a geosynchronous satellite, which in turn will transmit the signals to the territory of I. lAustralia.

Fig. 1 shows signal generating apparatus 10, which will be described in more S.".detail in relation to Fig. 2. A signal preferably an encoded and/or er,.rypted signal will be prepared using apparatus 10, and then sent to the RPN signal distribution centre for transmission from the RPN transmitters. Such transmissions could be made in a number of ways. The transmission could be a continuous transmission, or a periodic transmission during daylight hours, or at night. Preferably, the transmission would be arranged to take place in the early hours of the morning, when a paging network's normal load is at its lightest and 25 as a result transmitting capacity for the time signal is readily available. The |i encoding/encryption of the signal is necessary to ensure that unlicensed or nonaccredited timepieces are not able to decode the signal for time correction and Sother operations. A decoding key may be incorporated as an integral part of 1 electronic circuitry in a timepiece, or may be in the form of software, 'it may also I

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'7A 8 take the form of a Smart Card.

The signal generated by apparatus 10, which includes a real time message, is sent to the RPN signal distribution centre 12. According to the chosen option amongst those already discussed, the signal is sent for transmission to a plurality of transmitters, two of which are shown at 14 and 16. Although it is envisaged that each of the transmitters will transmit the same signal at the same time, it is quite likely that transmitters will send signals at different times. However, each transmitted signal will be a real time signal. Such transmitters are, as discussed previously, normally used to transmit signals which are adapted to be received by paging devices (not shown). Timepieces 18 and 22 are located remotely from transmitters 14 and 16, but each is in range of at least one transmitter. It may well be that timepiece 18 is in the Western Standard Time zone, and timepiece 22 is in the Eastern Standard Time zone.

Timepieces 18 and 22 preferabily include a radio receiver and control circuitry ,o 15 (shown in Fig. such that a time message signal transmitted from transmitter 14 or 16 is received by the receiver and decoded by the control circuitry to synchronize a clock mechanism in the timepiece to adjust the mechanism to the correct time. The clock may have an analog display (20) or a digital display (24).

:ii: Alternatively, the output from the control circuitry may consist of output means such as a digital signal, which may be directly or indirectly interfaced to a personal computer, slave clocks, cash register or other electronic equipment for the purpose of conveying correct time and/or time synchronizing, which may also include year, day and date information.

The clock mechanism's circuitry may be so arranged that the time (and the day, date and year information if they are included) is able to be synchronized as a Sresult of receiving the aforementioned signal to maintain the accuracy of the mechanism, or for updating the time for changes such as the entry into or the departure from Daylight Saving, or for the occasional corrections to UTC (Co- Sordinated Universal Time) time. As far as the latter is concerned, there are RAz 30 regular agreed corrections to time, often by the addition of a leap-second on a 41' 1- 9 predetermined date.

In Fig. 1, timepiece 18 is, or is connected tc, an analog clock whose display shows that the time is 10:07 Western Standard Time. In the preceding twentyfour hours, a signal has been received from transmitter 14 or 16 to correct the time on the display. Timepiece 22 is associated with a digital display, which shows the time to be 12:07:41 EST. It also has received a signal within the last twenty-four hours to correct the time.

There are many variations to the basic scheme described in relation to Fig. 1.

The time transmissions from transmitters 14,16 could be specific to a particular 10 time zone. Thus, transmitter 14, located in Western Australia, and all other transmitters in that time zone, could transmit a signal which related only to the Western Standard Time zone. Transmitter 16, located in the EST area, and any other transmitters in that zone, may only transmit a signal relevant to that zone.

Of course, for other areas of the world, a single time zone may include a number of countries.

However, the preferred form of the invention is to have a common signal transmitted from all transmitting sites within the region concerned, which in the Australian context means the whole country. Such a signal would contain a message giving the correct time for all time zones in the region, and would also include a code which would allow a decoding device to assign the correct time to the correct locality code so that when the time message is received and decoded the correct time for the particular time zone is determined.

As a preference, the device would include a switch or a series of switches which could be termed "locality switches". The locality switch could be set to program the time transmission decoder in the radio clock mechanism to keep the time for any locality included in the information transmitted by the signal. In normal use the switch would be set to the position for the time zone in which the clock i mechanism is located. However, by setting the switch to another position, a jI j A4/ display of the time in another zone may be obtained. A permanent setting of the 'T =s 2^ n~ 61~

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0 switch to another zone a zone anywhere in the world would be useful in locations where it is desired to know the time in that zone. Applications could be at airports, in financial dealers' offices and the like. In addition, in a place such as Broken Hill, which despite being in New South Wales has historically operated on Central Australian Time, a timepiece locality switch could be set to CST. This would be accomplished by comprehensive information being included in time signal transmissions. A locality switch may take the form of a single multiposition switch, a series of switches, a push-button arrangement, or software means.

Some persons like to operate with a clock which displays a time which is in advance of the correct time. For example, a person may wish to have a clock which is five minutes ahead of the actual time. Means may be provided such that the clock mechanism may display, instead of the correct time for a zone or locality, a time which is in advance or in retard of that time. It may be possible to select such an alternative display by providing one or more settings on the locality switch.

Fig. 2 is a block diagram in more detail of the transmission part of the embodiment of Fig. 1. A source 26 of accurate time preferably an atomic clock provides an output to a modem interface 28, which in turn outputs to a master time encoder 30. A personal computer interface 32 also outputs to master time encoder 30, and controls the preparation and output of the encoded signal to the RPN 12.

SThe master time encoder 30 produces an encoded and, encrypted real time message containing an identity code UTC time accurate to within 100 milliseconds, the digital inverse of the previous UTC time, UTC date (with year, \day of year, day of week, day of month and month of year redundant coding, Sdrte of next (if any) leap-second update, and time zone data consisting of data for up to sixteen time zones made up of the time for each time zone in plus or minus desired intervals from UTC time, together with date (if any) of the next Daylight Saving change and the direction o .hat change for that time zone. The .i jj R )00

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to 0* O 4 4 digital inverse of the previous UTC time is sent as well as real time UTC, to enable a comparison of the two pieces of information to be made by control circuitry at the timepiece, as a monitoring and checking measure. A preferred interval from UTC time may be 30 minutes, as throughout the world most if not all time zones are reckoned in half-hour or hour intervals from UTC time. It is preferred that a single signal, containing time zone data on sixteen time zones, be transmitted. Although at present there is only a maximum of eight time zones in place in Australia during any one period, should other areas be covered, the signal would have the capacity to service those areas.

Information on the next Daylight Saving change(s) is sent in advance of the earliest date, to enable the timepiece to reset the time, even if it does not receive a regular signal immediately after the change, or the preceding few signals. The information includes at least the date on which the change is to occur, and if required the time of the change, together with the direction and magnitude of the 15 change. Such Daylight Saving information may be routinely transmitted as part of each signal transmission, and may be stored by the timepiece and used by it to automatically effect the correct time adjustment for Daylight Saving when the real time in the timepiece corresponds to the time and date that has been routinely conveyed to the timepiece and stored. Following the change of the 20 time in the timepiece to or from the Daylight Saving time tha signal format would be reconfigured to routinely include information about the next correspondence between real time and the Daylight Saving time change required time for the purpose of changing the time at the correct Daylight Saving adjustment time.

By using such a system of sending information in advance on Daylight Saving changes, the requirement that the timepiece receive a specific signal transmission to initiate a Daylight Saving change is removed. Furthermore, the requirement that a Daylight Saving change signal be transmitted at a precise time to initiate the change is also removed. It follows that if for some reason a signal is not transmitted or received, such a change will still be made.

e re time generated time code ignal fed via a real time handshake The real time generated time code signal is fed via a real time handshake r i 1 ii I IYT 12 system to the RPN 12 for broadcast through transmitter 14. The handshake takes the form of the master encoder requesting the RPN for permission to feed data for transmission, an acknowledgment from the RPN 12, and the feeding of data from the encoder 30 to the RPN 12.

The format of the real time message to be transmitted is: <ID><Time></Time><Date><Leap-Second-Date><Time Zone Data> The preferred manner in which the time message signal is transmitted is for it to be traritnitted six times within a twenty-four hour period, with intervals of about five minutes between each transmission. It is envisaged that the preferred single S 10 signal, containing real time data on 16 time zones, would transmit in about seconds. Preferably, the first transmission would commence at around 02:00:30 i EST. That enables the handshake to take place immediately after 02:00:00, and the protocols of that mean that transmission may commence within a few milliseconds, consistent with an immediate acknowledgment of the request.

15 The circuit of Fig. 3 is that of a "receiving clock Fnechanism" which may be regarded as an embodiment c, timepiece 18 or timepiece 22 of Fig. 1. The mechanism consists of a conventional radio frequency pager "front end" receiving arrangement 34. The front end 34 provides either the raw POCSAG data or other data or decoded POCSAG message data to a microprocessor, microcomputer or similar processing unit. POCSAG is an acronym for the Post SOffice Code Standardization Advisory Group.

SAn input signal processing unit decodes the time data signal to reproduce the original time, date, leap-second date adjustment, time offsets to UTC time, the next Daylight Saving date, and the direction of change, for multiple time zones.

The time processing unit also receives external inputs at power up that instruct the processing unit what kind of output configuration to assume; examples are i RA&, pulse, serial, LCD, parallel bus, master or slave. The time processing unit also -On 313 B M N nt" 13 receives inputs from a time zone or locality switch to set the time zone or time locality to which displayed and/or outputted times are to be set. A user adjustment inputs to the processor to allow for user setting of time, date and alarm time and date information. Time zone, time, date, alarm and other data may also be set and altered by means of software commands received by parallel or serial input means.

The processor maintains a real time clock mechanism synchronized with UTC and date, derived from the decoded radio pager receive. signal. Initially the real time clock mechanism is set with the received time. For several days following, 10 the real time will not be reset with the latest received time. Instead, the latest received time will be stored and an adjustment will subsequently made to the displayed and outputted times. Thus, the real time clock mechanism will be allowed to drift, and after several days an accurate calculation of the direction and magnitude of the clock mechanism's drift will be made. That will enable the mechanism to self-calibrate, even in the absence of a time message signal. It will accordingly be possible for manufacturers to produce cost-effective, reliable clocks which will maintain accurate time even in the absence of receiving a radio time message signal for several days. This feature caters for the temporary lack of such a signal as a result of storm activity (thunderstorms causing electrical 20 activity), power failure at the transmitter, temporary location of a timepiece in a oo location where it cannot be reached by a signal, temporary location of a ar timepiece out of range of a transmitter, and so on. In such circumstances it can also be seen that the practice of sending information on Daylight Saving changes well ahead of the earliest date for any of those changes, enables a timepiece to be reset to the new time regime even if it has not received a signal for some time.

Each timepiece, especially timepieces 22 having a digital display, may display, upon selection, the date and time of tile next Daylight Saving change. In addition, a timepiece may show that it is in Daylight Saving mode. Furthermore, the display may indicate that the timepiece is out of range of a transmitter; a 4 simple "Out Of Range" message would suffice. In addition, the display, may also

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O 0 14 indicate that the displayed time is not accurate, when it has not been corrected for some time or at all, for whatever reason. It may be that the timepiece has never been in effective range, or log-term disturbances have prevented a good signal being received. In such cases, a message such as "Unreliable Time" or "Bad Time" would be shown.

An onboard clock mechanism memory will maintain time zone offset and daylight saving data (date and direction of changes), date, leap-second date, alarm mode, alarm time and date, time and oscillator adjustment constants, configuration mode, a history buffer of received time message radio signals, together with matching onboard real time clock time.

oC Time and date for the time zone selected shall be displayed and/or outputted S" and/or made available in one or more of several formats as selected by the configuration mode inputs to the processor. Some possible ways in which outputting of the time and date may take place are as follows: 15 Pulses at one-second intervals for analog clocks. Such pulses may be temporarily halted or fast stepped in order to synchronize an analog clock to real time. Output for one-minute or one-hourly pulses may also be provided. Reset output and "reset done" output provide the logic to reset the hands of the clock to a predetermined position.

An asynchronous serial communication output with or without a parity bit.

Interfacing to connected electronics may be via TTL logic levels RS232, RS422, RS485, infrared or optical means.

A half-duplex asynchronous serial communications interface which sends time, date and other data upon a request from connected electronics.

Interfacing to connecting electronics may be via TTL logic levels, RS232, SRS422, RS485, infrared or optical means.

LCD displayattached either directly or via LCD display driver electronics.

i 5 ^N r i Parall,; bus outputs.

A parallel bus interface which sends time, date and other data upon a request from connected electronics.

The processor also checks for errors in received radio pager data, loss of RF signal, low battery voltage and the lack of radio time update after several days.

Errors are indicated by several output signals including buzzer, low power, out of range and data error, and/or by status register accessible in half-duplex serial mode or parallel bus mode, or errors may be indicated in several ways on the LCD display.

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The circuitry of the module operates as follows when the unit is first powered up.

When power is applied, for example when a battery is inserted, the unit will stay in a powered up mode until time message signals are received, subsequently powering off until the next transmission is due. If, however, the timepiece is 1manually set after initial power up, it will then power off until the next signal S 15 transmission is due. The unit is provided with a battery-saving capacitor, such that if a battery is replaced within about a minute of removing the old one, the unit will not behave as if it has been powered up.

A power management unit within the processor keeps power usage to a minimum. This is considered to be of importance in the marketing of any battery-powered timepiece. It is intended that any such timepiece would have a life of at least a year, before battery replacement is necessary. It follows that power usage must be kept to a minimum. The radio pager front 34 is powered off except for an average of 12 minutes per day between 02:00:00 and 02:25:00.

This is accomplished by a polling facility. The front end is powered up daily to i 25 receive the group of signals. If a predetermined number of good signals in a group is received (for example, two good signals in a group of three signals, or Sthree in a group of six signals) the front end will power off, not being required to deal with any subsequently-transmitted signal. In general, electronics not in RA active use are powered down.

r C i: 16 The processor also maintains a watchdog timer. When the analog clock mode is not being used or half-duplex serial or parallel bus modes are in use, then unless a valid input from connected electronics other than front end 34 within a given time period (for example 25 hours) then a reset output is pulsed high or low in order to reset external mechanisms or electronics. A valid input is either a pulse input of defined maximum duration limits to the "reset done" input, or a valid software input command on either the parallel bus or serial inputs.

The module of Fig. 3 is adapted to form the core of a radio pager clock. Among the many variations on the basic theme of a radio pager clock, one may find analog clocks, LCD, LED and mechanical flip panel wall, desk and bedside clocks, clock plug-in boards for PCs, clocks which connect to a PC via the keyboard connector, RS232 serially interfaced time for general use and I connection to computers, and clock units on a RS485 bus. Apart from taking the i form of a plug-in circuit board for insertion into a vacant slot in a PC, the module may be incorporated into a separate stand-alone unit which is connected to one of the communications ports of the PC or adapted to be wired into the PC -4A. circuitry or included as an integral part of the PC circuit board design. Software may also be installed on a PC for the purpose of having the PC internal clock 4V slaved to the time message signal to maintain correct time and date. i 40 20 It is envisaged that reference timepieces will be located at particular locations, so that transmission delays may be adjusted for. Clearly, there will be measurable and differing delays between the generation of a particular signal and the receipt thereof by a timepiece. The reference timepieces, which may be located in each transmitter head, would be used to quantify particular delays so that a compensatory adjustment could be factored into the signal. If the paging network transmitted from a geosynchronous satellite, path differences to different places in Australia would be negligible, and it may then be able to make a singia signal adjustment.

Among the applications of the time synchronized timepiece of the present 0invention, one may envisage a digital time display on a pager, in a motor vehicle, -S -it 17 as a part of a wristwatch, as part of airconditioning controls, security entrance controls, as part of time-locks for safes, on telephones and in elevators.

Since modifications within the spirit and scope of the invention may readily be effected by persons skilled in the art, it is to be understood that the invention is not limited to the particular embodiments described, by way of example, hereinabove.

Modifications which are envisaged by the applicant include the use of single or multiple transmitters in and around Australia, the use of TV and/or AM, FM and shortwave radio transmitters. The time message signal may also be transmitted 10 from a satellite.

at$ The entire contents of the specifications lodged with provisional applications nos.

PM4730 and PM5097 are hereby imported into this specification and form part of the disclosure of this specification. The claims also form part of the disclosure of this specification.

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Claims (25)

1. Apparatus for synchronizing a timepiece to a reference time, including: means to receive and decode a transmitted signal, said signal including information relating to said reference time; 1 means to extract from the decoded signal information relating to the correct time for a preset time zone, locality or offset; means to display or to output said correct time; and i means adapted to store daylight saving change information included in said signal, in advance of the date and time specified for a change to or from daylight saving time, so that in the absence of a specific signal S. transmission to initiate a daylight saving change, a time correction can still be made on the date and at the time specified for said change. i

2. Apparatus according to claim 1, further including means to facilitate the display of the date and time of the next daylight saving change. a 0

3. Apparatus according to claim 1 or 2, further including means to facilitate the display of the fact that the time is daylight saving time.

4. Apparatus according to any preceding claim, further including a locality switch which is adapted to be set to a particular zone, locality or offset, thus Scadsing the correct time for that zone, locality or offset to be displayed,

5. Apparatus according to any preceding claim, further including means to facilitate the display of the fact that the displayed time is not reliable.

6. Apparatus according to any preceding claim, further including means to ll~s~ i' s: i; 19 facilitate the display of the fact that the timepiece is out of range of a transmitter of the said signal.

7. Apparatus according to any preceding claim, further including means to ensure that when said apparatus is powered up, said apparatus remains in a signal receive mode until the next signal transmission takes places, unless there occurs a manual time setting operation.

8. steps *e A method of synchronizing a timepiece to a reference time, including the of: generating a signal which includes information relating to said reference time, and information relating to the date and time of a change to or from daylight saving time; transmitting said signal from a transmitter in advance of said date and time of said change to or from daylight saving time; receiving and decoding said signal at or in the vicinity of said timepiece; processing said signal to enable said timepiece to display a time, or generate an output representative of said time, said time being the correct time for a preset zone, locality or offset; extracting from the decoded signal information relating to the correct time for a preset time zone, locality or offset; displaying or outputting said correct time; and storing said information on the date and time of a change to or from daylight saving time, included in said signal, so that even in the absence of a specific signal transmission to initiate a daylight saving change, a time correction can still be made on the date and at the time specified for said change. i P i :i 1 I~ i tr p1

9. A method according to claim 8, further including the step of displaying the date and time of the next change to or from daylight saving time.

A method according to claim 9, further including the step of facilitating the display of the fact that the displayed time is daylight saving time.

11. A method according to claim 8, claim 9 or claim 10, further including the step of ensuring that when said timepiece is powered up, said timepiece remains in a signal receive mode until the next signal transmission takes places, unless there occurs a manual time setting operation.

12. A method according to any one of claims 8 to 11, further including the C 0 o 0 10 step of operating a locality switch on said timepiece, which locality switch is adapted to be set to a particular zone, locality or offset, thus enabling the correct time for that zone, locality or offset to be displayed.

13. A method according to any one of claims 8 to 12, further including the step of facilitating the display of the fact that the displayed time is not reliable.

14. A method according to any one of claims 8 to 13, further including the C• step of facilitating the display of the fact that the timepiece is out of range of a transmitter of the said signal.

A method according to any preceding claim, wherein the signal contains the following information: an identity code; S|UTC time; the digital inverse of the previous UTC time; UTC date; i P I 21 date of next (if any) leap-second update; and time zone data.

16. A method according to any preceding claim, wherein the format of the signal is: <ID><Time></Time><Date><Leap-Second Date><Time Zone Data>

17. A method according to claim 15 or claim 16, wherein the time zone data includes data for each of a predetermined number of time zones.

18. A method according to claim 17, wherein the predetermined number is 16.

19. A method according to claim 17 or claim 18, wherein the signal is 10 comprised of the time for each zone in plus or minus intervals from a reference time, together with date (if any) of the next daylight saving change and the direction of change.

20. A method according to any preceding claim, wherein said reference time is UTC time. 15

21. A method of setting a timepiece in accordance with a signal containing S. data on a daylight saving time change, including: transmitting said signal in advance of the date and time of said daylight saving time change contained in said data; receiving said signal at or in the vicinity of a timepiece; decoding said signal; storing said data; and *1 i 22 setting, at said date and contained in said data, said timepiece to daylight saving time.

22. A timepiece adapted to receive and decode a signal containing time zone data for a number of time zones, and data on a daylight saving change, including: means to store said data on a daylight saving change in advance of the predetermined date and time of said change so that the time alteration consequent upon said changes may be effected for that timepiece on said predetermined time and date, even if no further specific signal transmission to initiate a daylight saving change is received. ii 1 S S 9

23. A method of synchronizing a timepiece to a reference time, as herein described, with reterence to the accompanying drawings.

24. Apparatus for synchronizing a timepiece to a reference time, as herein described, with reference to the accompanying drawings.

25. A timepiece adapted to be synchronized to a reference time, as herein described with reference to the accompanying drawings. substantially substantially substantially :t i i i 11' i DATED this 30 October 1998 JOHN CHRISTIANSEN Member, Federation Internationale des Conseils en Propri6te Industrielle (International Federation of Industrial Property Attorneys) Patent Attorney for the Applicant: SH.P.M. TECHNOLOGIES PTY. LTD. i ABSTRACT r 14L .t 9 9, A method and apparatus for synchronizing a timepiece to a reference time includes the preparation (10) of an encoded and/or encrypted signal for transmission from a paging network (12) transmitter (14,16). The signal, which contains a time message P-nd information on Daylight Saving changes and corrections to UTC time, is transmitted a number of times in a twenty-four hour period, with brief intervals between each transmission. A timepiece (18,22) has a receiver and control circuitry (34) which receive and decode the signal. The decoded time information is used to automatically set the time of the timepiece (18,22) to the correct time for a predetermined time zone. A locality switch is provided on the timepiece (18,22) to determine which time zone time is to be displayed (20,24). 4: .1