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BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to an electronic conference system for
conducting a remote conference among a plurality of offices, and more
particularly, to a remote conference system employing electronic board
units, in which the supervision, update and control of picture data are
improved.
(2) Description of the Prior Art
In recent years, as a device to allow a conference between conference
members remote from each other, an electronic board unit has been
developed as an alternative to a conference telephone or a conference
integrated television/telephone system.
The conference telephone or the conference integrated television/telephone
system achieve their object of enabling a remote conference to be held.
However, the conference telephone system can transmit only audio signals
and, therefore, has a disadvantage in that it cannot supply the conference
members with sketches or other handwritten material during the conference.
On the other hand, the conference integrated television/telephone system
can pick up handwritten materials and transmit them in the form of visual
signals, i.e., pictures, greatly assisting the members of a remote
conference. However, to transmit the picked up hand-written materials, the
transmission line must have a wide bandwidth. Also, the television camera
viewing area at the transmission side that can be picked and transmitted
up is relatively small. Therefore, the conference integrated
television/telephone system has a disadvantage in that it is difficult to
transmit materials written on a wide board. Thus, an electronic board
unit, which can transmit the data for material handwritten on a board
having a wide area and display the transmitted pictures at a receiving
station, has been provided
In an electronic conference system employing the electronic board units,
material is handwritten, by means of, for example, a felt pen or a marker
pen, on an input board, e.g., a tablet or a digitizer, so that the
handwritten input data is input and stored at one station or office
(hereinafter referred to as a station). The handwritten input data is
transferred through a telephone line to a remote station and the received
pictures are displayed there on a display unit such as a CRT monitor or a
projector. Since the handwritten input data can be transmitted along with
audio signals, the use of an electronic board unit is of great assistance
to the members of a remote conference.
In the electronic conference system employing the electronic board units,
by including color data in the handwritten input data, color pictures also
can be displayed on a color picture display unit. In addition, the
displayed materials can be recorded as hard copies.
Generally, in a remote conference, the members of the conference each use
respective picture display units, during the conference for displaying
pictures, which receive picture data from respective storage units (for
example, floppy disks). In this case, it is often necessary, in view of
the object of the conference, to display the same picture simultaneously
on all of the picture display units. The picture data for constructing
such a picture is usually previously formed by a member of the conference,
and is recorded in the storage unit at his or her station. The picture
data is also transferred through transmission lines to the respective
picture display units and recorded in their respective storage units.
During a conference, it is desired that, when one of the members of the
conference designates a common picture number for the picture being
displayed on the picture display unit, the same picture can be displayed
at the other respective picture display units. When a correction is added
to previously formed and/or recorded picture data, a new picture number
must be provided and registered. In this situation, it would be desireable
to record (duplicate) the same picture data in respective storage units in
a plurality of offices remote from each other, and to provide a picture
number (an absolute number) common to the respective picture display units
to the same picture data. However, such an electronic conference system
for use in this case is not known.
In a conventional electronic conference system employing electronic board
units, picture data of a picture written at a first station is provided
with a picture number which can only be used in that first station. When
the picture data formed at the first station is transferred to a second
station and stored in the storage unit in the second station, the picture
data is, conventionally, provided with another picture number, usually
different from the picture number provided at the first station.
Therefore, the same picture data has different picture numbers at each
respective station. Accordingly, it is difficult to simultaneously display
the same picture at different stations. To simultaneously display the same
picture at different stations, the picture data of the picture being
displayed at the first station is transferred to the other stations. This,
however, requires transmission lines with a high transmission capacity or
otherwise limits the transmission speed and, as a consequence, the display
speed.
Even if a common absolute number is assigned to the same picture data
stored in individual storage units of the stations remote from each other,
so that the same picture data is commonly controlled in each respective
station, a further disadvantage occurs when an addition or a correction is
made to an existing picture data which has been numbered with a common
absolute number. That is, in this case, the added or corrected picture
data has an absolute number different from that of the original picture
data. Therefore, when the added and corrected part of the picture data is
to be transmitted to a remote station, the entire set of picture data must
be transmitted even when the added and corrected part is very small.
This also causes a requirement for transmission lines with a high
transmission capacity or again limits the transmission speed.
Further, even when the same picture can be simultaneously displayed at
different stations, it is often necessary for a different picture to be
displayed at one of the stations.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide an electronic
conference system for a remote conference among a plurality of stations,
in which, when the same picture data is stored in respective storage units
of stations remote from each other, the same picture can be simultaneously
displayed at the different stations by providing, to the same picture
data, an absolute number common to all of the stations, without further
transmitting the same picture data from one station to another.
Another object of the present invention is to provide a system such as the
above, in which, when a correction or an addition is made to the same
picture data at one station, only the corrected or added part of the
picture data is transmitted, as a differential or correction data, from
one station to another, wherein the corrected or added part of the picture
data is added to the same picture data in the other station without
retransmitting the entire set of original picture data.
Still another object of the present invention is to provide a system such
as the above, in which each of the stations has two modes of operation,
i.e., a common mode and an individual mode, which modes are automatically
or manually switched over, and, when one station is in the common mode of
operation, the same picture as that displayed at the other stations in the
common mode is displayed at that station, whereas, when one station is in
the individual mode of operation, a picture individually specified at that
station is displayed independently from the picture displayed at the other
stations in the common mode.
A still further object of the present invention is to improve the
coordination supervision and control of the picture data by providing a
system such as the above.
A further object of the present invention is to reduce the needed
transmission capacity of a transmission line between remote stations by
providing a system such as the above.
A further object of the present invention is to increase the data
transmission speed by providing a system such as the above.
A further object of the present invention is to provide a system such as
the above in which a convenient system for assigning identification
numbers to individual storage units is provided.
To attain the above objects, an electronic conference system is provided
for a remote conference among a plurality of stations, in which each of
the stations has a data input unit for inputting picture data, a storage
unit for storing picture data of plural pictures and a display unit for
displaying each of the pictures one at a time. Also included is a control
unit connected to the data input unit, the storage unit, and the display
unit, for controlling the storing of picture data input from the data
input unit or transferred from another station, for controlling the
display on the display unit, for controlling the transmitting of picture
data stored in the storage unit to the other station, and for controlling
the receiving of picture data transferred from the other station. In these
stations, the control unit includes: absolute number providing means for
providing a first absolute number for picture data when the picture data
of the picture is input from the data input unit in one of the stations
and absolute number transmission means for transmitting the first absolute
number to the other station of the stations. Also included in the control
units are picture data transmitting means for transmitting the picture
data provided with the first absolute number to the other station only
when the other station does not have the number equal to the first
absolute number and absolute number receiving means for receiving a second
absolute number from the other station when picture data is formed in the
other station. Further included are discriminating means for
discriminating whether or not the storage unit stores the number equal to
the second absolute number from the other station and discriminating
result transmission means for transmitting the result of the
discrimination by the discriminating means to the other station. Picture
data receiving means for receiving a picture data is also provided, in the
other station, with the second absolute number, the other station being
adapted to transmit the picture data with the second absolute number in
response to the information received from the discriminating result
transmission means, this information indicating that the storage unit has
not stored the number equal to the second absolute number; so that, the
same picture data of the same pictures stored in respective storage units
in respective stations is supervised or coordinated by the same absolute
number at connected stations.
The control unit in the station further includes a write control means for
writing an absolute number, provided in the station or transferred from
the other station, into the storage unit in the station, absolute number
specifying means for specifying an absolute number corresponding to a
picture to be displayed, and read control means for reading picture data
of a picture to be displayed, by searching using an address of the picture
data in the storage unit, this address corresponding to the absolute
number specified by the absolute number specifying means.
The storage unit in each of the stations includes a first area for storing
the absolute numbers and a second area for storing the picture data of the
plural pictures corresponding to the absolute numbers in a one by one
correspondence. Each of the absolute numbers includes a first number for
indentifying a storage unit in which the absolute number is originally
stored, and a second number for specifying the address in the storage unit
of picture data of a picture to be displayed.
Each of the absolute numbers further includes a third number, the third
number representing the number of additions to the picture corresponding
to the absolute number including the third number. When an addition is
made, by means of the data input unit, to a picture being displayed at the
first station, the absolute number providing means forms a new absolute
number corresponding to the added part of the new picture data. The
absolute number transmission means transmits the new absolute number to
the second station, and the picture data transmitting means transmits the
added part of the new picture data to the other station.
The electronic conference system further includes switching means for
switching the operation of the first station between a common mode of
operation for displaying, in the station, a picture which is the same as
the picture displayed in the another station when the other station is in
the common mode of operation, and an individual mode of operation for
displaying, in the station, a picture corresponding to an absolute number
specified, independently from the other station, by the absolute number
specifying means in the station.
The storage unit stores a plurality of location numbers, each of the
absolute numbers stored in the storage unit corresponding to one of the
location numbers, and, by specifying a desired one of the location numbers
in the absolute number specifying means, a desired picture is displayed.
The storage unit stores a plurality of location numbers, each of the
location numbers corresponding to one group of absolute numbers having the
same first and, second numbers and different third numbers, and by
specifying a desired one of the location numbers in the absolute number
specifying means, a desired picture including additions or corrections is
displayed.
The electronic conference system also includes first number determining
means for determining the first number for identifying a storage unit,
including initialization means for initializing the storage unit, the
first number being determined based on the time necessary for the
initialization.
The first number is determined based on a predetermined lower bits obtained
from the time necessary for the initialization.
BRIEF DESCRIPTION OF THE DRAWINGS
The above objects, features, and advantages of the present invention will
be more apparent from the following description of the preferred
embodiments with reference to the accompanying drawings, in which:
FIG. 1 is a schematic block diagram of a picture data transfer in an
electronic conference system according to the present invention;
FIG. 2 is a schematic block diagram of an absolute number transfer in an
electronic conference system according to the present invention;
FIG. 3 is a schematic block diagram of an individual mode of operation in
an electronic conference system according to the present invention;
FIGS. 4A and 4B are schematic block diagrams of a conventional electronic
conference system, to explain the problems therein;
FIGS. 5A and 5B are schematic block diagrams of an electronic conference
system according to the present invention, in which two stations have or
do not have common picture data provided with a common absolute number;
FIG. 6 is a schematic block diagram of an electronic conference system
according to the present invention, in which only an added part of picture
data is transferred from one station to another;
FIG. 7 is a schematic block diagram of an electronic conference system
according to the present invention, in which one station is in the
individual mode of operation;
FIG. 8 is a block diagram illustrating the general composition of an
electronic conference system according to the present invention;
FIG. 9 is a table illustrating the relationship between the location number
in a storage unit, the absolute number, and the picture data;
FIG. 10 is a block diagram illustrating an embodiment of the control unit
in the system shown in FIG. 8;
FIG. 11 is a block diagram illustrating another embodiment of the control
unit in the system shown in FIG. 10;
FIG. 12 is a diagram of the structure of the storage unit according to an
embodiment of the present invention;
FIGS. 13A and 13B together form a flowchart illustrating a sequence of
processes when a new picture data is formed according to an embodiment of
the present invention;
FIG. 14 is a diagram of the structure of the storage unit according to
another embodiment of the present invention;
FIG. 15 is a diagram illustrating four storage units, to explain a problem
when additions or corrections are effected on original data;
FIGS. 16A and 16B together form a flowchart illustrating a sequence of
processes when an addition or correction is effected on an existing
picture data; FIG. 17 shows respective states of the storage unit 7 during
the processes shown in FIGS. 13A, 13B, 16A, and 16B;
FIG. 18 is a block diagram illustrating the composition of an
identification number determining system according to an embodiment of the
present invention;
FIG. 19 is a block diagram illustrating an absolute number providing unit
according to an embodiment of the present invention; and
FIG. 20 is a table showing the contents of the absolute number/supervising
memory in the unit shown in FIG. 19.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Before describing the preferred embodiments of the present invention, the
fundamental functions of a remote conference system according to the
present invention will be described with reference to FIGS. 1 through 9.
FIG. 1 is a schematic block diagram of picture data transmission in an
electronic conference system according to the present invention. In FIG.
1, three offices or, in other words, stations A, B, and C remote from each
other are illustrated. All of the stations are provided with display units
D.sub.A, D.sub.B, and D.sub.C, respectively displaying the same picture,
illustrated by a symbol XXX. After the picture XXX is originally formed in
station A, station A transmits the picture data of the picture XXX to
stations B and C. Stations B and C then display on their display units
D.sub.B and D.sub.C the same picture XXX. This is the basic and
fundamental function needed for carrying out a remote conference, and is
achieved according to the present invention as described later in more
detail.
FIG. 2 is a schematic block diagram of an absolute number transfer in an
electronic conference system according to the present invention. In FIG.
2, the three remote stations A, B, and C have storage units S.sub.A,
S.sub.B, and S.sub.C in addition to the display units D.sub.A, D.sub.B,
and D.sub.C. The storage units S.sub.A, S.sub.B, S.sub.C are, for example,
floppy disks. The data stored in these storage units S.sub.A, S.sub.B, and
S.sub.C are as indicated by reference symbols C.sub.A, C.sub.B, and
C.sub.C, respectively. In station A, the storage unit S.sub.A stores
picture data for a picture illustrated by a symbol XX. In station C, the
storage unit S.sub.C also stores the picture data for the same picture as
that illustrated by the symbol XX. However, in station B, the storage unit
S.sub.B does not at first store the same picture data of the picture XX.
The picture data of the picture XX in each of the stations A and C is
provided with an absolute number A-1. The absolute number is a page
identification number associated with a particular page at all times and
throughout the conference network. When the theme of the conference
relates to the picture XX, and the picture XX is to be displayed at all of
the stations, station A transmits the absolute number A-1 to stations B
and C. Station C can identify that it has the same absolute number as the
absolute number A-1 transmitted from station A. However, station B does
not have the absolute number A-1 and informs station A that station B does
not have the absolute number A-1. Station A then transmits the picture
data of the picture XX only to station B, which then displays, based on
the transmitted picture data from station A, the picture XX on its display
unit D.sub.B. Station C displays the picture XX on its display unit
D.sub.C, based on the picture data from its storage unit S.sub.C. Thus, by
labelling the picture data with an absolute number common to all of the
stations, the picture data need not be transferred to the other station
when it has the same absolute number as the number transmitted from the
other station.
FIG. 3 is a schematic block diagram of an individual mode of operation in
the electronic conference system according to the present invention. In
FIG. 2, the next main theme of the conference relates to a picture YY, the
picture data of which is labelled with an absolute number A-2. The picture
data of the picture YY, in this case, is stored only in the location
number 2 of the storage unit S.sub.A. The display unit D.sub.A displays
the picture YY based on the picture data in the storage unit S.sub.A.
Station A transmits the picture data of the picture YY to stations B and
C. In station C, the picture data transmitted from station A is input into
the display unit D.sub.C and the picture YY is displayed thereon. Also,
the picture data is input to the storage unit S.sub.C and is stored
therein. However, in station B, the picture data transmitted from station
A is input only to the storage unit S.sub.B, and is stored therein. The
display unit D.sub.B displays the picture XX labeled with the absolute
number A-1 and does not display the picture YY labeled with the absolute
number A-2. That is, in this case, station B selects an individual mode of
operation, and station C selects a common mode of operation. Since the
storage unit S.sub.B in station B now stores the picture data of the
picture YY, the contents of the storage unit S.sub.B coincide with the
progress of the conference. Thus, any one of the stations can select an
individual mode in which any desired picture stored in its storage unit
can be specified to be displayed, or a common mode in which a picture
common to all of the stations is displayed.
FIGS. 4A and 4B are schematic block diagrams of a conventional electronic
conference system, to explain the problems therein. In the prior art, no
absolute number is labeled is provided for the picture data of one
picture. Only a number of contents, or a location number in the storage
unit, is provided for each set of the picture data. The numbers of
contents, i.e., the location numbers, are sequentially provided in each of
the storage units. In FIG. 4A, stations A and B are associated by a
communication line l. Station A includes a display unit D.sub.A and a
floppy disk F.sub.a. Station B includes a display unit D.sub.B and a
floppy disk F.sub.b. The floppy disk F.sub.a stores picture data for a
picture XX in the location number "1". The floppy disk F.sub.b stores the
same picture data for the picture XX as above in its location number "1".
In this state, by designating the location number "1" at both station A
and B, the same picture XX is displayed on both the display units D.sub.A
and D.sub.B. However, assume that the floppy disk F.sub.a is replaced by
another floppy disk F.sub.c, as illustrated in FIG. 4B, the display unit
D.sub.A then may display another picture ZZ different from the original
picture XX. Because, in this case, the floppy disk stores, in its location
number "1", the picture data of the picture ZZ. Thus, in the prior art,
even when the same content number is designated at different stations, the
displayed pictures are not necessarily the same.
FIGS. 5A and 5B are schematic block diagrams of an electronic conference
system according to the present invention, in which two stations have or
do not have common picture data provided with a common absolute number.
According to the present invention, each set of picture data for one
picture is labeled with an absolute number, e.g., b-1-1 or c-1-1. As
illustrated, each of the absolute numbers consists of three symbols, i.e.,
a first symbol such as b or c, a second symbol following the first symbol,
in FIGS. 5A and 5B, equal to "1", and a third symbol following the second
symbol, in FIGS. 5A and 5B, is equal to "1". The first symbol identifies a
floppy disk in which the corresponding picture data is originally formed
and stored; the second symbol indicates a content number in the identified
floppy disk; and the third symbol indicates the number of corrections
effected on the original picture data. The third symbol thus may be
referred to as an editing symbol.
In FIG. 5A, the only difference from FIG. 4B is that each set of picture
data stored in respective storage units F.sub.B and F.sub.C is labelled
with an absolute number consisting of three symbols. In operation, the
picture data for the picture XX is formed first in station B and is stored
in the floppy disk F.sub.b with the absolute number b-1-1. The first
symbol "b" indicates that this picture data is originally stored in the
floppy disk F.sub.b. The second symbol "1" indicates that this picture
data is stored in the location "1" in the floppy disk F.sub.b. The third
symbol "1" indicates that this picture data is the first addition, or no
correction has been made to this picture data. By specifying the second
symbol on a keyboard (not shown) in station B, the picture data with the
absolute number b-1-1 is input to the display unit D.sub.B and the picture
XX is displayed thereon. The absolute number b-1-1 is also transmitted
through the transmission line l to station A. In station A, a search is
conducted for the absolute number equal to the number b-1-1 transmitted
from station B. If the same absolute number is not found in the floppy
disk F.sub.c, as in the case of FIG. 5A, then station B transfers the
picture data corresponding to the absolute number b-1-1 to station A.
Station A displays the picture based on the picture data transmitted from
station B, and, simultaneously, stores the picture data with the
corresponding absolute number b-1-1 into an appropriate vacant location
(in FIG. 5A, into location number 2) in the storage unit F.sub.c.
If the floppy disk F.sub.c has already stored therein the picture data with
the absolute number b-1-1, as shown in FIG. 5B, the absolute number equal
to the number b-1-1 transmitted from station B is found. In this case,
station A informs station B that station A has the picture data with the
absolute number b-1-1. Station B then, in response to the information from
station A, does not transmit the picture data.
In FIGS. 5A and 5B, the third symbol in the absolute number is not used.
The effective use of the third symbol is described with reference to FIGS.
6 and 7.
FIG. 6 is a schematic block diagram of an electronic conference system
according to the present invention, in which only added picture data is
transmitted from one station to another. In FIG. 6, the floppy disk
F.sub.c in station A previously stores the picture data with the absolute
number c-1-1 and the picture data with the absolute number b-1-1. The
floppy disk F.sub.b in station B previously stores the picture data with
the absolute number b-1-1. Initially, the picture XX is displayed on both
the display units D.sub.A and D.sub.B based on the picture data with the
absolute number b-1-1 stored in the floppy disks F.sub.c and F.sub.b.
In this state, assume that a new picture Z must be added to the displayed
picture XX in, for example, station B. Picture data of the picture Z is
then formed in station B and is stored with a new absolute number b-1-2 in
a vacant area in the area of the location number "1" for the original
absolute number b-1-1 in the floppy disk F.sub.b. Note that, to express
that the new picture is the part added to the original picture XX, the
third symbol of the new picture data is revised to "2", and the first and
the second symbols "b" and "1" remain as originally designated. The added
part of the picture data with the absolute number b-1-2 is then
transmitted to station A. In station A, when the added part of the picture
data is received, it is stored in a vacant area in the area of the
location number "2" with the original absolute number b-1-1 in the floppy
disk F.sub.c. Thus, by designating the absolute numbers b-1-1 and b-1-2, a
revised picture XXZ is displayed on both the display units D.sub.A and
D.sub.B. The absolute numbers b-1-1 and b-1-2 can be designated by
specifying the location number "1" in station B or the location number "2"
in station A.
FIG. 7 is a schematic block diagram of an electronic conference system in
which one station is under the individual mode of operation. In FIG. 7,
the stored contents of the floppy disks F.sub.c and F.sub.b are initially
the same as the stored contents of the final stage of the floppy disks
F.sub.c and F.sub.b, as illustrated in FIG. 6. That is, the floppy disk
F.sub.c previously stores the picture data with the absolute numbers
c-1-1, b-1-1, and b-1-2. Also, the floppy disk F.sub.b previously stores
the picture data with the absolute numbers b-1-1 and b-1-2.
In this state, when the theme of the conference is changed so that the
picture YY must be displayed, the display unit D.sub.A fetches the picture
data with the absolute number c-1-1 and displays the picture YY. Further,
the picture data with the absolute number c-1-1 is transferred to station
B and is stored in an area of a location number 2, for example, of the
floppy disk F.sub.b. Station B, however, selects the individual mode of
operation requiring that the picture XXZ being displayed should be
maintained on the display unit D.sub.B. Thus, even when the new picture
data with the absolute number c-1-1 is transmitted from station A, the
picture YY is not displayed in station B under the individual mode of
operation. The picture data with the absolute number c-1-1 is merely
stored in the floppy disk F.sub.b.
Embodiments of the present invention will now be described in detail in the
following.
FIG. 8 illustrates the general construction of an electronic conference
system according to the present invention. In FIG. 8, a first station 1 on
one side is connected through a communication line l such as a telephone
line, etc., to a second station 1'. The first station 1 is provided with a
digitizer unit 2 for inputting handwritten data, a document input unit 3,
which is a scanner unit for inputting existing documents, a display unit 4
such as a CRT monitor or a projector for displaying the handwritten data
or the documents, a keyboard unit 5 for inputting operating instructions,
etc., a control unit 6, and a storage unit 7, such as a floppy magnetic
disk unit for filing or storing picture data. The digitizer unit 2 is
provided with a tablet i.e., an electronic board.
In operation, assume that picture data X is first formed in the first
station 1 by an input from the digitizer unit 2 or the document unit 3.
Then, an absolute number F is assigned to the picture data X, as described
in detail later. The picture data X and its absolute number F are stored
in a location number n in the storage unit 7. As described before, the
absolute number F consists of three symbols, i.e., the first symbol for
identifying the storage unit 7 in which the picture data is first stored,
the second symbol indicating the location of the stored picture data in
the storage unit 7, and the third symbol indicating the number of
corrections made to the original picture data X. Therefore, the location
number n of the storage unit 7, into which the picture data is first
stored, is the same as the second symbol.
FIG. 9 is a table illustrating the relationship between the location number
L, the absolute number Ab, and the picture data PD. As shown in FIG. 9,
the area of the location number 1 stores an absolute number F.sub.a and
its corresponding picture data A; the area of the location number 2 stores
an absolute number F.sub.b and its corresponding picture data B; the area
of the location number n stores the absolute number F and its
corresponding picture data X; and so forth. The location numbers 1, 2, . .
. , n, . . . are sequentially assigned in accordance with the sequence of
the formation of the picture data.
Referring back to FIG. 8, to simultaneously display the picture for the
picture data X on both the display units 4 and 4', an operator inputs, by
means of the keyboard unit 5, the second number n which is, in the station
where the picture data X is originally formed, the same as the location
number n. In response to the input in the keyboard 5, the control unit 6
reads the picture data X and its corresponding absolute number F. The
picture data X is then input into the display unit 7, which then displays
the picture for the picture data X. The control unit 6 simultaneously
transmits the absolute number F through a communication line l to the
second station 1'. The second station 1' then searches its storage unit 7'
for the number equal to the absolute number F.
If the absolute number F is found in the storage unit 7', the control unit
6' in the second station 1' informs the control unit 6 in the first
station that the storage unit 6' has already stored the absolute number F.
In this case, the storage unit 6' reads the picture data X corresponding
to the absolute number F and inputs it to the display unit 4'. Thus, the
same picture of the picture data X is displayed on both the display units
4 and 4'.
If the absolute number F is not found in the storage unit 7', the control
unit 6' informs the control unit 6 that the storage unit 6' has not stored
the absolute number F. In this case, the control unit 6 automatically
transmits the picture data X corresponding to the absolute number F to the
control unit 6'. The control unit 6' then assigns the absolute number F to
the picture data X and stores the assigned absolute number F and the
transmitted picture data X in the storage unit 7', and also displays the
picture for the picture data on the display unit 4'. Thus, the same
picture for the picture data X is displayed on both the display units 4
and 4'. By previously establishing a relationship between a location
number n' in the storage unit 7' and the absolute number F, an operator at
the second station 1' can designate the picture for the picture data X to
be displayed on both the display units by inputting the number n' from the
keyboard unit 5'.
Thus, the picture data having the common absolute picture number F is
simultaneously displayed on the display units 4 and 4' by means of the
control units 6 and 6'.
Also, in the electronic conference system shown in FIG. 8, during the
display of the picture stored in the storage units 7 and 7', additions or
corrections can be carried out to the picture being displayed by means of
the digitizer unit 2 or 2'. In this case, the original picture a is
defined to have an absolute picture number X having a third number 1. The
added or corrected part of the picture is assumed to be designated as b.
The new picture is then given as a+b. The absolute number for the picture
b is given as X' and is stored in the storage unit 7 or 7' in the station
at which the additions or corrections to the original picture a are
carried out. In the new absolute number, the first and the second numbers
are respectively equal to those in the original absolute numnber. The
third number, i.e., 2, in the new absolute number X', however, is
different from the third number; i.e., 1, in the original absolute number.
When additions or corrections are made to an existing picture at the first
station 1, this results in the second station 1' not having the picture
data provided with the new absolute nu | | |
