Note: Descriptions are shown in the official language in which they were submitted.
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SYNCHRONIZATION OF A TIMEPIECE TO A REFERENCE TIME
BACKGROUND OF THE INVENTION
Field of the Invention
This invention relates to improvements in the synchronization of a timepiece to a
5 referel1ce time, and in particular, relates to an improved method and apparatus for
synchronizing a timepiece to such a time.
In this speciricalion, 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.
10 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
15 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 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
20 (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
25 clocks one hour ahead of the relevant Standard time for a period of some months
between spring and autumn each 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
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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. New South Wales has subsequently agreed to use the same dates as
Victoria and Tasmania for the end of Daylight Saving, however, there are still difficulties
5 for persons, particularly business persons, in the various States and Territories which are
normally in the one time zone.
Despite the problems caused by having between three and five time zones, and thetwice-yearly change of the time régime in all but three of the eight States and Territories,
most timepieces in Australia operate independently of each other, and require a manual
10 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 also has a representative
15 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
20 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.
Description of the Prior Art
25 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
21 ~1063
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 the correct time for the
time zone in which the timepiece is located.
AU-B-83677/91 (643824) by NEC Corporation, published on 12 March 1992, relates to
5 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. A powerful VLF transmitter broadcasts signals which are received by a large
10 number of clocks throughout Europe (much of which operates on Central European
Time), and which synchronizes those clocks, bringing each of them to the correct time.
There is clearly a need for a system in Australia and other countries which is able to
remotely synchronize and reset timepieces. For example, it is essential to be able to
maintain the correct time on timepieces - most of which have digital displays - which are
15 associated with personal computers, cash registers, fax machines, automated teller
machines (ATMs), debit and credit card terminals, and so on. 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 present clocks used in such applications drift alarmingly over
20 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.
BRIEF SUMMARY OF THE INVENTION
It is an object of this invention to provide an improved system for the synchronization of
25 a timepiece to a reference time.
The invention provides a method of synchronizing a timepiece to a reference time,
inciuding the steps of:
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generating a signal which includes information relating to said reference time;
transmitting said signal from a transmitter;
receiving 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.
The invention also provides 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;
means to extract from the decoded signal information relating to the correct time
for a preset time zone, locality or offset; and
means to display or to output said correct time.
The invention further provides a timepiece adapted to be synchronized to a reference
15 time, including:
receiver means adapted to receive a signal containing time zone data for a
plurality of time zones;
control circuitry for decoding said signal; and
locality switch means for selecting one of a number of predetermined time
régimes;
such that said circuitry sends to a display, or to other apparatus, a time signal
2 1 (~ /063
representative of the correct time for the selected predetermined time régimes.
The invention also provides a timepiece adapted to receive and decode a signal
containing time zone data for a number of time zones, and data on daylight saving
changes, including:
means to store said data on daylight saving changes so that the time alteration
consequent upon said changes may be effected for that timepiece on a stated timeand date, even if no further signal is received.
The invention further provides a method of setting a timepiece in accordance with a signal
containing data on daylight saving time changes, including:
transmitting said signal;
receiving said signal at or in the vicinity of a timepiece;
decoding said signal;
storing said data; and
setting, at a time and on a date contained in said data, said timepiece to a new1 5 time.
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;
transmitting said signal from a transmitter;
receiving said signal at or in the vicinity of said timepiece; and
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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.
The invention also provides apparatus for synchronizing a timepiece to a reference time,
5 including:
means to receive and decode a transmitted signal, said signal including information
relating to said reference time;
means to extract from the decoded signal information relating to the correct time
for a preset zone, locality or offset; and
means to display or to output said correct time.
The invention further 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;
transmitting said signal from a transmitter;
receiving said signal at or in the vicinity of said timepiece; and
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.
The invention also provides apparatus for synchronizing a timepiece to a reference time,
20 including:
means to receive and decode a transmitted signal, said signal including information
reiating to said reference time;
21 ~3/063
means to extract from the decoded signal information relating to the correct time
for a preset zone, locality or offset; and
means to display or to output said correct time.
The invention further provides a method of synchronizing a timepiece to a reference time,
5 including the steps of:
generating a first signal;
transmitting said first signal;
receiving said first signal;
composing a second signal consequent upon receipt of said first signal, said
second signal including information relating to the precise time of receipt of said
first signal; and
transmitting said second signal.
The invention also provides a system for synchronizing a timepiece to a reference
timepiece, said system including means connected to a transmitter, said transmitter being
15 adapted to transmit a first signal to a timepiece, said means being adapted to receive
said first signal and to compose a second signal including information on the precise time
of receipt of said first signal, said second signal being adapted to be transmitted by said
transmitter.
The invention further provides a system for synchronizing a timepiece to a reference time,
20 said system including:
means to generate a first signal;
transmission means to transmit said first signal;
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monitor means connected to said monitor means for receiving said first signal and
for composing a second signal related to said first signal, said signal thereafter
being transmitted by said transmission means; and
means associated with said timepiece for commencing a count and receipt of said
first signal, and for using the information from said count and from informationcontained in said second signal to generate accurate time.
The invention also provides, in a method of synchronizing a timepiece to a reference
time, where a signal is transmitted to said timepiece to enable to time kept or displayed
by said timepiece to be synchronized to a reference time, the step of including additional
10 information, when received by a timepiece, results in a predetermined message or the like
being displayed.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig 1. is a block diagram of one embodiment of a method and apparatus for
synchronization of a timepiece to a reference time;
Fig 2. is a block diagram of the signal generation and transmission aspect of the
arrangement of Fig. 1; and
Figs. 3a and 3b are two parts of a circuit diagram of one embodiment of
receiving/decoding apparatus.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
20 The block diagram of Fig. 1 represents an arrangement which utilises the Telstra Radio
Paging Network (RPN). The RPN is adapted to send messages to paging devices carried
by persons. Although at the present time the RPN does not service the entire area of
Australia, it can reach some 90% of the population, and Telstra is committed to an
expansion of the network. The network is currently operated by sending signals by
25 landiines to master transmitters, which relay signals to a larger number of slave
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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 Australia.
In networks such as the Telstra RPN, paging receivers (not shown) usually have an
individual address commonly called a Cap.Code (CC), which allows a specific message
5 to be sent to a particular paging receiver, which is the core business of such a network.
However, if a single message is to be sent to a group of paging receivers, a common
Cap.Code is used and a group call may be made that simultaneously conveys the
information concerned to all the receivers in the group, which have that common
Cap.Code.
10 Fig. 1 shows signal generating apparatus 10, which will be described in more detail in
relation to Fig. 2. A signal - preferably an encoded and/or encrypted 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
15 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 as a result transmitting capacity for the time signal is readily available. The
encoding/encryption of the signal is necessary to ensure that unlicensed or non-accredited timepieces are not able to decode the signal for time correction and other
20 operations. A decoding key may be incorporated as an integral part of electronic circuitry
in a timepiece, or may be in the form of software. It may also 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
25 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
30 are adapted to be received by paging devices (not shown). Timepieces 18 and 22 are
21 87363
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 preferably include a radio receiver and control circuitry (shown in
5 Fig. 3), 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). Alternatively, the output from the control
circuitry may consist of output means such as a digital signal, which may be directly or
10 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 result of receiving
15 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-ordinated Universal Time) time. As far as the latter
is concerned, there are regular agreed corrections to time, often by the addition of a
leap-second on a predetermined date. While UTC time - which is equivalent to
20 Greenwich Mean Time - is referred to throughout the specification and claims, local time,
which is in itself derived from UTC time, may well be substituted when accurate time is
being sourced, and any reference to UTC time may be seen to include local time.
In Fig. 1, timepiece 18 is, or is connected to, an analog clock whose display shows that
the time is 10:07 Western Standard Time. In the preceding twenty-four hours, a signal
25 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 time zone. Thus,
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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
5 time zone may include a number of countries.
However, the preferred approach would be 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
10 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
15 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 mechanism is located. However,
by setting the switch to another position, a display of the time in another zone may be
obtained. A permanent setting of the 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.
20 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 multi-position switch, a
25 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
30 in retard of that time. It may be possible to select such an alternative display by providing
~ 21 ~ J63
12
one or more settings on the locality switch.
Fig. 2 is a block diagram in more detail of the transmission part of the approach of Fig.
1. A source 26 of accurate time, for example an atomic clock or an on-line modem feed
of correct time, which is commercially available, provides an output to a modem interface
5 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.
The master time encoder 30 produces an encoded and encrypted real time message
containing, apart from the Cap.Code applicable, an identity code (ID), UTC time accurate
10 to within 100 milliseconds or better, 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, date of next (if any) leap-second update, and time zone data consisting of data
for a plurality of time zones, for example 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
15 (if any) of the next Daylight Saving change and the direction of that change for that time
zone. The 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
20 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,
25 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 change. Such Daylight Saving
information may be routinely transmitted as part of each signal transmission, and may be
30 stored by the timepiece and used by it to automatically effect the correct time adjustment
21 ~7063
13
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 time in the timepiece to or from the Daylight Saving time the signal format would be
reconfigured to routinely include information about the next correspondence between real
5 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
10 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.
The real time generated time code signal is fed via a real time handshake system to the
RPN 12 for broadcast through transmitter 14. The handshake takes the form of the15 master encoder requesting (A) the RPN for permission to feed data for transmission, an
acknowledgment (B) from the RPN 12, and the feeding of data (C) from the encoder 30
to the RPN 12.
The format of the real time message to be transmitted may be:
<ID>~Time></Time><Date><Leap-Second-Date><Time Zone Data>
20 The preferred manner in which it has been suggested that the time message signal is
transmitted is for it to be transmitted six times within a twenty-four hour period, with
intervals of about five minutes between each transmission. It is envisaged that the
preferred single signal, containing real time data on 16 time zones, would transmit in
about 4.5 seconds. Preferably, the first transmission would commence at around
25 02:00:30 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.
~! 87063
~ 14
The circuit of Fig. 3 is that of a "receiving clock mechanism" which may be regarded as
a variant of timepiece 18 or timepiece 22 of Fig. 1. The mechanism consists of aconventional 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
5 data to a microprocessor, microcomputer or similar processing unit. POCSAG is an
acronym for the Post Office Code Standardization Advisory Group.
An 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.
10 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 pulse, serial,
LCD, parallel bus, master or slave. The time processing unit also 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
15 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 time and
date, derived from the decoded radio pager received signal. Initially the real time clock
20 mechanism is set with the received time. For several days following, 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.
25 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 activity), power failure
30 at the transmitter, temporary location of a timepiece in a location where it cannot be
21 87~63
~ 15
reached by a signal, temporary location of a timepiece out of range of a transmiKer, 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 régime even if it has not received a
5 signal for some time.
Each timepiece, especially timepieces 22 having a digital display, may display, upon
selection, the date and time of the 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 simple "Out Of Range" message would
10 suffice. In addition, the display may also 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.
15 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.
20 Time and date for the time zone selected shall be displayed and/or outputted 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:
Pulses at one-second intervals for analog clocks. Such pulses may be temporarilyhalted 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.
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16
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, RS422, RS485,
infrared or optical means.
LCD display attached either directly or via LCD display driver electronics.
Parallel 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
15 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.
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
20 next transmission is due. If, however, the timepiece is manually set after initial power up,
it will then power off until the next signal 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
25 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
2 1 8 71~63
17
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 receive the group of signals. If a predetermined number of good
5 signals in a group is received (for example, two good signals in a group of three signals,
or three in a group of six signals) the front end will power off, not being required to deal
with any s~lhse~uently-transmitted signal. In general, electronics not in active use are
powered down.
The processor also maintains a watchdog timer. When the analog clock mode is not10 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
15 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 serially20 interfaced time for general use and connection to computers, and clock units on a RS485
bus. Apart from taking the 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 circuitry or included as an integral part of the PC circuit board design. Software may
25 also be installed on a PC for the purpose of having the PC internal clock slaved to the
time message signal to maintain correct time and date.
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
30 timepiece. The reference timepieces, which may be located in each transmitter head,
21 ~7063
~ 18
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 single signal adjustment.
5 Among the applications of the time synchronized timepiece of the present invention, one
may envisage a digital time display on a pager, in a motor vehicle, 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.
Modifications which have been envisaged include the use of single or multiple transmitters
10 in and around Australia, the use of TV and/or AM, FM and shortwave radio transmitters.
The time message signal may also be transmitted from a satellite.
Another embodiment of the present invention relates to the previously-described system
using the Telstra Radio Paging Network, or a similar network. It is also applicable to any
other suitable type of signal-transmitting infrastructure.
15 The approach has been to provide a 'real time' signal to enable timepieces to be
synchronized to a reference time. It has already been acknowledged that true real time
signalling is difficult if not impossible to achieve due to transmission delays, and for that
reason the provision of monitoring apparatus in, on or near transmitter heads issuggested as a way to adjust for factors such as the difference distances - and hence
20 signal transmission times - between a transmitter and a number of timepieces.
In addition, there can be problems in the transmission of signals from a paging network.
Generally, messages are sent to a network via a telephone system, and enter a queue.
Depending on the number of messages already in the queue, there could be quite adelay before a time synchronization signal is transmitted. In both Australia and in other
25 countries, it may not be technically feasible to 'queue-jump' with a time synchronization
signal. Even if it were possible, some paging network operators may not be prepared to
allow queue jumping. After all, their main business is the transmission of messages to
paging devices.
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One embodiment of this invention attempts to overcome such problems by providing a
monitor within transl"ission range of a transmitter which monitor is adapted to receive
signal transmissions from that transmitter head. The monitor is preferably connected in
some way to the transmitting network, and to be able to send a message on the network.
5 A monitor may be physically placed at the transmitter site, or alternatively, could be
connected via a link such as a modem, with a known fixed delay.
In its simplest form, the embodiment envisages transmitting a first signal, which may be
regarded as a start signal or 'mark'. That first signal or mark would be sent to the paging
network as generally described earlier in this specification, and may well wait in a queue
10 before being transmitted. A typical queue delay may be about five minutes.
The receipt of the mark signal by a timepiece would start an internal counter within the
timepiece. The signal is also noted by the monitor, which is in the transmitting coverage
area of the transmitter. The monitor notes the precise time the first signal (mark) was
received by it. The monitor would then compose a second signal which includes
15 information on the precise time of receipt of the first signal. That second signal would
then be sent to the transmitter for transmission. A timepiece, on receiving the second
signal would apply that precise or accurate time sent by the second signal to the elapsed
time on the counter, to provide an extremely accurate time or display on the timepiece
or in any other way already envisaged by this specification.
20 The second signal may be sent at any time after the first signal, the only limiting factor
being a desire to limit battery use in a timepiece. It is quite unlikely in any paging
network that a delay of more than five minutes would occur between the generation of
the first signal and its transmission. It is accordingly suggested that in this embodiment
each timepiece should be gated "on" for about ten minutes, each time a transmission is
25 expected.
By way of example, a first signal could be sent at four times in each 24-hour period,
including a preferred transmission around 2:00 am local time to cater for Daylight Saving
changes, as discussed earlier in this specification.
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Some, or each first signals could be a simple signal, or a mere mark, or could include all
of the information (and more) which signals, previously discussed in this specification,
have. Regardless of the content of the first signal, each second signal would have to
contain at least the precise time information referred to earlier.
5 A preferment could involve a first signal being a simple, short signal, with the
corresponding second signal containing all other necessary and/or desired information.
The second signal, each signal, or the first signal, could contain additional information.
Paging transmitters tend to be arranged in groups to cover various localities. For
example, the greater Melbourne area may have five transmitters. They may all send their
10 time synchronization signals at the same time. However, transmissions in the Gippsland
area of rural Victoria may be unrelated in time to those for the Melbourne area.
There may be a circumstance were a mobile timepiece moves between different areas
during the period between a first signal (mark) and a second signal. Such a timepiece
may receive a "Melbourne mark" and a "Gippsland second signal" or correction. The
15 timepiece would end up with an incorrect time. To avoid such a circumstance, each
group of transmitters may include an identification code with each transmission, so that
correct first signals may be correlated with correct second signal corrections/calibrations.
The use of such a "tag" in an ID code would prevent the mis-application of a correction
to the wrong area, and ensure that the applicable correction for the area in which the
20 timepiece is located, would be made. This also applies to a fixed timepiece which may
receive signals from a transmitter located in, or broadcasting to, a different area.
It is envisaged that with this non real time variant, Daylight Saving pre-alerts would still
be included in each group of transmissions so that even if a timepiece does not receive
its message at 2:00 am local time on the appropriate day it will still already correct the
25 time on the correct date.
As has been stated some or all and/or additional information, to that discussed in general
earlier in this specification, may be included in one or both signals. Such things as the
pre-alert Daylight Saving correction and the date are included in that information, as is
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the facility for time zone data for a plurality of time zones to be included in a signal
transmitted in one time zone.
In a method of transmitting a signal used to synchronize a timepiece to a reference time,
in accordance with this invention, particularly in relation to the embodiment in which the
5 signal is sent via a paging network, the signal may contain additional information, such
that that additional information, when received by a timepiece (18,22) or the like, results
in a message being displayed on the timepiece or elsewhere, or another function of or
associated with the timepiece may be controlled.
For example, the signal may contain information which enables a particular message to
10 be displayed on all timepieces (18, 22), or only on those in a particular time zone or a
particular grouping, or only on a specific timepiece. In that manner, a message
containing information which is of personal or general application, such messages as
advertisements, weather forecasts or warnings, news flashes - or birthday greetings -
could be sent via the system, and displayed on the timepiece display. Such a display
15 may utilise the existing alphanumeric display of a timepiece displaying digital time, or may
involve the adaption of, or addition to, any display to represent an alphanumeric
message. It may be that in any signal containing such a message, the informationrelating to the time may be omitted, although it would be advantageous in alwaysincluding time update information.
20 As has been stated, each timepiece may be individually addressable. This may be
achieved by the use of multiple Cap.Codes, typically four, for each timepiece, receiving
clock mechanism or the like, each of which would be individually addressable. In that
way, there would be a plurality of ways in which a given population or the like could be
signalled, including the individual addressing of each timepiece.
25 For example, a particular timepiece may have a second, unique, Cap.Code which could
be addressed with a message for its owner. Such a message could be a birthday
greeting, a reminder or the like, which would be displayed on the timepiece as previously
described.
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22
Alternatively, a signal sent in accordance with this invention may contain, in addition to
previously-described information, an internal address within the signal format, by way of
a sub-address beyond a common Cap.Code, so that even though all timepieces (18,22)
or the like with that CC receive the signal, only the group of timepieces, or an individual
5 timepiece, with the appropriate internal individual and/or group address will respond in
some predetermined manner. It may be considered convenient for the serial number of
a ti",epiece to be utilised in the creation of an individual address.
One application of the individual addressability of a timepiece (18,22) is to remotely
enable or disable a function of the timepiece. It is envisaged that in practice, timepieces
10 (18, 22) in accordance with the present invention will be subjected to service agreements
which involve a periodical fee being paid by a person in return for which service for the
timepiece will be provided for that period.
In order that such fees are paid, it may be necessary for the timepieces to be provided
with means to enable each one to be individually disabled and enabled. Accordingly, it
15 would be possible, should the fee not be paid for a particular timepiece, for a or the signal
to contain information which causes that timepiece to be disabled, such that it could no
longer receive (or display) time updates, and/or any additional messages or the like. In
the event that the fee is subsequently paid, the or a signal may include information which
results in the timepiece being enabled. The enabling and disabling may be effected by
20 the relevant part of the signal acting to set bits in a timepiece (18, 22) or the like.
The enable/disable facility may be utilised in relation to any service taken by the
timepiece or the like. For example, a person may subscribe to two services, such as time
updates and weather messages, but may be in default in relation to periodical payments
on only one service. The enable/disable facility may be used to switch off access to the
25 facility for which payment is in default. Similarly, a new subscriber to a service may have
the appropriate service enabled on the timepiece in question, subsequent to a first service
payment. The enable/disable facility may be used to switch on and off any service to a
timepiece or the like.
lt should also be noted that in the event that in any jurisdiction there was a change in
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time zone policy - such has been discussed in South Australia, with a suggested move
to Eastern Standard Time - it would be possible in accordance with this invention to
download a software set to a timepiece, to cater for such a policy change.
One desirable form of unit capable of rapid deployment in a particular area for the
5 provision of signals according to this invention transmitted via a paging network is a
"Paging Time Master Generating Unit". Such a unitl which could be located in a box or
in something like a suitcase, would preferably include a computer such as an IBM-
compatible PC, a modem which is adapted to communicate with the paging network and
with a telephone network for providing faxed error reports and the like, a monitor for
10 receiving signals broadc~.st from a paging network transmitter, and a source of accurate
time.
Such a unit may be easily located on or in the vicinity of a transmitter, and with minimal
connections may commence the transmission of timepiece-synchronizing signals in
accordance with this invention. The computer, which of course is run on proprietary
15 software, receives data from the transmitter, and also accurate time. The latter may be
obtained from an atomic clock which may also be included in the unit, but it is more
convenient to obtain accurate time via the modem from an on-line time service such as
Telstra's Compuline.
The unit carries out the method of this invention as described in this specificationl and
20 connects with the paging network, preferably through a dial-up connection using the
modem. With the Paging Time Master Generating Unit, and with some timepieces
adapted to be synchronized in accordance with the invention, it would be possible to go
to a particular time zone, and/or a particular country, and start a time synchronization
system virtually immediately.
25 Clearly, a system other than a paging network could be used. For example, signals could
be sent on a television or radio network. However, paging networks are more suitable,
as they are geared to be a telephone messaging service.
Preferably, timepiece hardware and/or software would be able to operate with both real
21 87063
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time signals and with the arrangement envisaged by the present invention.
Alternative embodiment is suggested to cope with the possibility, however unlikely it may
be, of data being inadvertently corrupted in the time transmitting means or encoding
means within the RPN, which may result in all timepieces receiving the corrupted signal
5 and accordingly displaying a corrupted and thus incorrect time.
One embodiment envisages the timepieces which receive the time signal mark and
update do not accept the data contained therein until a third, "confirmation" signal is
received. Such a third signal is sent out over the RPN after a master unit located in the
RPN coverage area, and having an accurate source of time such as an accurate real time
10 clock, receives the time update and determines that the updated time is correct. If the
tested time is cGr,ecl, a "confirm" signal is sent to all timepieces.
Alternatively, if the master unit determines that the updated time is incorrect, an "ignore"
signal is sent out over the RPN, as a result of which the timepieces do not accept the
time as correct. During a predetermined time period, for example 15 minutes, after
15 receipt of the update signal, the timepieces do not accept the time sent as correct, while
the "ignore" signal is being sent out over the RPN.
