facsimile
Click on the red underlined text to get to the source
...
The object of a facsimile system is to reproduce
faithfully a document or image from one piece of paper
...
... onto another piece of paper sited remotely from the
first one. Up to now, the main method of facsimile
communication has been via the telephone network. Most
...
... communication has been via the telephone network. Most
facsimile machines permit neither the storage of image
page nor their modification before transmission. With
...
... page nor their modification before transmission. With
such machines, it is almost impossible to communicate
between different makes of facsimile machines. In this
respect, facsimile machines fall behind other
...
... between different makes of facsimile machines. In this
respect, facsimile machines fall behind other
electronic communication services.
...
... services.
Integration of a facsimile service with computer
communication techniques can bring great improvements
...
... improved but, more important, the system can be
integrated with other forms of data communication.
Moreover, the computer enables the facsimile machine to
fit into a complete message and information processing
environment. The storage facilities provided by the
...
... environment. The storage facilities provided by the
computer system make it possible to store large amounts
of facsimile data and retrieve them rapidly. Data
conversion allows facsimile machines of different types
...
... of facsimile data and retrieve them rapidly. Data
conversion allows facsimile machines of different types
to communicate with each other. Furthermore, the
facsimile ...
... facsimile machines of different types
to communicate with each other. Furthermore, the
facsimile image is edited and/or combined with other
forms of data, such as text, voice ...
... In the Department of Computer Science at UCL, a
computerised facsimile system has been developed in
order to fully apply computer technology, especially
communication, to the facsimile ...
... facsimile system has been developed in
order to fully apply computer technology, especially
communication, to the facsimile field. Some work has
been done to improve the facsimile service ...
... communication, to the facsimile field. Some work has
been done to improve the facsimile service in several
areas.
...
... areas.
(1) Adaptation of the facsimile machine for use with
computer networks. This permits more reliable and
...
... point-to-point transfers.
(2) Storage of facsimile pages. This permits the
queueing of pages, so saving operator time. Also,
standard documents can be kept permanently and
...
...
(3) Interworking with other facsimile machines. This
permits different makes of facsimile machines to
...
... Interworking with other facsimile machines. This
permits different makes of facsimile machines to
exchange images.
...
...
(4) Compression of the facsimile images. This allows
more efficient transmission to be achieved.
...
... (6) Improvement of the images. The ability to 'clean'
the facsimile images not only allows for even
higher compression ratio ...
... destination.
(7) Editing of facsimile pages. This includes the
ability to change pictures, alter the size of
images ...
... electronically.
(8) Integration of the facsimile service with other
data types. For the time being, coded character
...
... service with other
data types. For the time being, coded character
text can be converted into facsimile format and
mixed pages containing pictures and text can be
manipulated.
...
...
This note first considers the functions of the
facsimile system, the related experimental work being
reported. Then the discipline for the system design ...
... system design is
discussed. Finally, the implementation of the UCL
facsimile system is described. As appendices, detailed
description of the system are given, namely
...
...
The computerised facsimile system we have developed
is composed of an LSI-11 micro-computer running the MOS
...
... [17], a Grinnell colour display [18], a DACOM facsimile
machine [16], and a VDU as the system console. This
...
... Network Interface
Fig. 1 Schematic of UCL facsimile system
In this system, a page is read on the facsimile ...
... facsimile system
In this system, a page is read on the facsimile
machine and the image data produced is stored on the
...
... remote site, the image data may be processed and
printed on a facsimile machine.
On the other hand, we can receive image ...
...
Section 2.1 dicusses the problems concerned with
transmission of facsimile image data over a network,
...
... image data.
In order to interwork with other facsimile machine,
we have to convert the image data from one
...
... image may be improved and more efficient
storage and transmission can be achieved. Secondly, a
facsimile editing system can be supported whereby a
picture can be changed and/or combined with other
pictures. This is described in section 2.4.
...
... into its bit-map representation format so that it can
be handled as a facsimile image and merged with
pictures. This provides an environment where multi-type
information ...
...
The first goal of our computerised facsimile system
is to use a computer network to transmit data between
...
... is to use a computer network to transmit data between
facsimile machines which are geographically separated.
Normally, facsimile ...
... facsimile machines which are geographically separated.
Normally, facsimile machines are used in association
with telephone ...
... telephone equipment, the data being sent along
telephone lines. Placing the facsimile machines on a
computer network presents a problem as the facsimile ...
... facsimile machines on a
computer network presents a problem as the facsimile
machine does not have the ability to use a computer
network ...
... network tasks a
computer is required, and so the first phase was to
attach the facsimile machine to a computer.
The facsimile ...
... facsimile machine to a computer.
The facsimile machine is not like a standard piece of
computer equipment. We required a special hardware
...
... hardware
interface to enable communication between the facsimile
machine and a small computer. This interface was made
...
... to appear exactly like the telephone system to the
facsimile machine. Furthermore, the computer was
programmed to act exactly as if it were another
facsimile ...
... facsimile machine. Furthermore, the computer was
programmed to act exactly as if it were another
facsimile machine on the end of a telephone line. Thus
the local facsimile ...
... facsimile machine on the end of a telephone line. Thus
the local facsimile machine could transmit data to the
computer quite happily, believing that it was actually
talking to a remote facsimile ...
... facsimile machine could transmit data to the
computer quite happily, believing that it was actually
talking to a remote facsimile machine on the other end
of a telephone wire. Because of the property of the
...
... At the other side of the computer network there was a
similar computer with an identical facsimile machine.
The problem of transmitting a facsimile ...
... facsimile machine.
The problem of transmitting a facsimile picture now
appeared simple: data was taken from the facsimile
...
... transmitting a facsimile picture now
appeared simple: data was taken from the facsimile
machine into the computer, transmitted over the network
...
... network
as if it was normal computer data, and then sent from
the computer to the facsimile machine at the remote
end. The data being sent over the network appears
...
... exactly as any other computer data; there is nothing
special about it to signify that it came from a
facsimile machine. The schematic of such facsimile
transfer system is shown in Fig. 2.
...
... special about it to signify that it came from a
facsimile machine. The schematic of such facsimile
transfer system is shown in Fig. 2.
...
... +-----+ +--+ +---+
Fig. 2 Facsimile transfer system
The experimental ...
... transmission is the quantity of data. Even with data
compression, a single page of facsimile data can
produce as much computer data as would normally be
sufficient for sending over 20,000 alphabetic
...
... network
we were using was often unable to keep up with the
speed of the facsimile machine. When this happened the
US UK
...
... +---+
Fig. 3. The three participants of the facsimile experiments
computer tried to slow down the facsimile ...
... facsimile experiments
computer tried to slow down the facsimile machine. The
facsimile machine would detect this 'slowness' as a
...
... computer tried to slow down the facsimile machine. The
facsimile machine would detect this 'slowness' as a
communication problem (as a telephone line would never
...
... mid-way through the page.
This is because the the facsimile machine we were
using was never intended for use on a computer; it was
designed and built for use on telephone ...
... telephone lines. Indeed,
being unaware that it was connected to a computer, the
facsimile machine transmitted data at a constant rate,
which exceeded the limit that the network could accept.
...
... to use over it.
Both these problems are surmountable. Facsimile
machines are coming on the market that are designed for
direct communication with a computer. These machines do
...
... tolerant of the stops and re-starts. On the other hand,
if there were a serious use of facsimile machines on a
computer network, the network ...
... computer where the data could be held prior to
transmission. The transfer of a page is now done in
three stages. First, the facsimile data is read from
the facsimile machine and stored on a local disk. This
...
... three stages. First, the facsimile data is read from
the facsimile machine and stored on a local disk. This
takes place at high speed as this is just a local
operation. When this is complete, the data is sent
...
... network to a disk on the remote computer.
Finally, the data from that disk is output to the
remote facsimile machine. This improved system is
shown in Fig. 4.
...
... The idea behind this method is to decouple the
facsimile machine from the network communications. The
data is read from the facsimile ...
... facsimile machine from the network communications. The
data is read from the facsimile machine at full speed,
without the delays caused by the computer network.
...
... place at whatever speed the network can sustain. This
does not affect the facsimile machines at all; they are
not involved in the sending or receiving. Only when all
...
... receiving. Only when all
the data has been received at the remote disk is the
remote facsimile machine told that the data is ready.
The facsimile ...
... facsimile machine told that the data is ready.
The facsimile machine is then given the data as fast as
it will accept it.
...
... telephone system where
the operator has to keep re-dialing the remote
facsimile machine until the call is answered.
...
... Facsimile machines ...
...
As was mentioned earlier, facsimile machines produce
a large amount of data per page due to the way in which
the pages are encoded. To reduce the data that has to
...
... be transmitted, various compression techniques are
employed. The manufacturers of facsimile machines have
developed proprietary ways in which the data is
compressed and encoded. Unfortunately this has meant
...
... compressed and encoded. Unfortunately this has meant
that interworking of different facsimile machines has
been impossible. In the system described in the last
section, exchange of pictures was only possible between
...
... been impossible. In the system described in the last
section, exchange of pictures was only possible between
sites that had identical facsimile machines. The new
set of CCITT recommendations will reduce the extent to
which differences in equipment persist.
...
... opportunity to manipulate data in any way we wish. In
particular we could convert the data from the form used
in one facsimile machine to that required by another.
This means that interworking between different types of
...
... This means that interworking between different types of
facsimile machines can be achieved.
The development of this system took place in two
...
...
The development of this system took place in two
stages: the decompression of the facsimile data from
the coded form used in our machine into an internal
data form and the recompression of the data in the
...
... techniques. In particular, we developed programs to
handle the recently approved CCITT recommendation for
facsimile compression [15]. The CCITT came up with two
...
... being used.
Unfortunately there were no facsimile machines on the
network that use the CCITT compression ...
... described in more detail in [13]. Essentially, these
show that the DACOM technique used by our facsimile
machine is comparatively poor, and that considerably
less data need be transmitted if some other method ...
...
One area that we have explored is the use of devices
other than facsimile machines for outputting the data.
Facsimile machines are both expensive to buy and
...
... other than facsimile machines for outputting the data.
Facsimile machines are both expensive to buy and
relatively slow to operate. We have investigated the
use of a TV-like screen to display the data, just as
...
... considerable effort.
The problems arise in the way that the facsimile
image is encoded. Raw facsimile ...
... facsimile
image is encoded. Raw facsimile images consist of rows
of small dots, each dot recorded as a black or white
...
... up a picture in a similar manner to the way in which a
newspaper picture is made up. Unfortunately the number
of dots used in a facsimile page is not the same as the
number used on most screens. For instance, the DACOM
facsimile ...
... facsimile page is not the same as the
number used on most screens. For instance, the DACOM
facsimile machine uses 1726 dots across each page, but
across a screen there are usually just 512 dots. Thus
to show the picture on the screen the 1726 dots must be
...
... elements that
the problem arises. We could just every third dot or
so from the facsimile page and just display those.
Alternatively, we could take three or more at a time
and try to convert the group ...
... black or white dot. Unfortunately, in both these
cases, data can get lost that is necessary to the
picture. For instance, a facsimile encoding of an
architect drawing could easily end up with a complete
...
... image on
a screen as well as output the image on a facsimile
machine. To a user of a computerised facsimile system
...
... image on a facsimile
machine. To a user of a computerised facsimile system
this could be a very useful feature: images can be
...
... this could be a very useful feature: images can be
displayed on screen much faster than on a facsimile
machine, and displays are significantly cheaper than
the facsimile ...
... facsimile
machine, and displays are significantly cheaper than
the facsimile machines as well. It is possible that an
installation could have many screen displays where the
image ...
... installation could have many screen displays where the
image could be viewed, but perhaps only one facsimile
machine would be available for hard copy. This would be
similar to many computer configurations today where the
...
... edges were very rough,
unexpected notches and excrescences being caused by the
facsimile scanner. They not only degrade the image
quality but also decrease the compression ...
... easier processing by the computer. As described
earlier, the image from the facsimile machine is
compressed in order to reduce the amount of data. The
cleaning allows a higher compression ...
... readability. In the end, we found that improving the
readability was very difficult, especially because the
facsimile image was so poor. Instead we found that the
effect of reducing the compressed output was more
...
...
By editing we mean that the facsimile picture can be
changed, or combined with other pictures, while it is
stored inside the computer. In previous sections it
...
... stored inside the computer. In previous sections it
was mentioned that we could change the size and shape
of a facsimile image. This technique was later combined
with an overlaying method ...
... in succession on the left, and areas selected and moved
to the right. Finally, the right-hand screen could be
printed on the facsimile machine.
The selection of an area of the picture was done by
...
... keep another scaled copy for display. This is due to
the fact that the screen had a different dimension to
that of the facsimile machine. The editing operations,
e.g. chopping and merging, were performed on the
original image ...
... facsimile machine can be viewed in a wider
context than merely a facsimile input/output device. It
can work as a printer for other data representation
...
... graphics. At present, text can be converted into
facsimile format and printed on the facsimile machine.
Moreover, mixed pages containing pictures and text can
...
... graphics. At present, text can be converted into
facsimile format and printed on the facsimile machine.
Moreover, mixed pages containing pictures and text can
be manipulated by our system. The integration of
...
... Moreover, mixed pages containing pictures and text can
be manipulated by our system. The integration of
facsimile images with geometric graphics is a topic of
...
...
In order to convert a character string into its
facsimile format, the system maintains a translation
table whereby the patterns of the characters available
in the system can be retrieved. The input character
...
...
This allows for more interesting applications of the
facsimile machine. For example, it could serve as a
Teletex printer, provided that the Teletex character
font is included in our system. In this case, the text
...
... type information can be
transmitted over a network. So far as this facsimile
system is concerned, a mixed page containing text and
pictures can be sent only when it has been represented
...
...
Now let us discuss the general disciplines for design
and implementation of a computerised facsimile system
which carries out the functions described in the
previous sections. Having discussed the requirements ...
...
In a computerised facsimile system, the images are
represented in a digital form. To carry out this
...
... represented in a digital form. To carry out this
conversion, a page is scanned by the optical scanner of
the facsimile machine, a digital number being produced
to represent the darkness of each pixel. As high
resolution has to be adopted to keep the detail of the
...
... high
resolution has to be adopted to keep the detail of the
image, the facsimile data files are usually rather
large. In order to achieve efficient storage and
transmission, the facsimile ...
... facsimile data files are usually rather
large. In order to achieve efficient storage and
transmission, the facsimile data must be compressed as
much as possible.
...
... much as possible.
Currently, the facsimile machines made by different
manufacturers h different properties, such as
different compression methods ...
... compression methods and different resolution.
There are also some international standards for
facsimile data compression, which are employed for the
facsimile ...
... facsimile data compression, which are employed for the
facsimile data to be transferred over the public data
network. These require that the facsimile ...
... facsimile data to be transferred over the public data
network. These require that the facsimile data be
converted from one representation form to another, so
that users who are separated geographically and use
...
... request processing facilities of the system as well.
When being processed, the facsimile image should be
represented in a common format or internal data
structure ...
... I/O activities of the physical devices, such as
facsimile machine, display and floppy disk. This
layer frees the task modules of upper layer ...
... and recompression routines convert data structures
of facsimile image information so that the
facsimile ...
... facsimile image information so that the
facsimile machines can communicate with the rest
of the system. Processing primitives, e.g.
chopping, merging, scaling, are implemented as
...
... different networks to which the UCL system is attached.
In our computerised facsimile system, these task
modules are implemented as separate processes. The
operation of the system relies on the communication
...
... Another important aspect of the multi-process
architecture of the UCL facsimile system, is the need
to systematise the control and organisation of the
tasks. This activity is the function of the task
...
...
In a modular, multi-process system such as the UCL
facsimile system, the structure of the interface
routines is very important. The CSI of section 3.3 is
...
... UCL FACSIMILE SYSTEM ...
...
Now we discuss the implementation of the computerised
facsimile system developed in the Department of
Computer Science at UCL.
...
... 24], and the Cambridge Ring. The form of network
connection is discussed further in section 4.3. The
system must transfer data between the facsimile devices
and the disks, and between the networks and the disks.
...
... As mentioned in section 2, apart from the general
purpose system console, there are three devices in the
system to support the facsimile service. These are:
...
...
(1) AED62 Floppy Disk, which is used as the secondary
memory storing the facsimile image data. Above its
driver, a file system ...
... image data has to buffered on a temporary file
lest time-out occurs on the facsimile machine.
(2) DACOM Facsimile ...
... facsimile machine.
(2) DACOM Facsimile Machine, which is used to input
and output image data. It reads an image ...
... image. Above its driver, there is a
interface task to fit the facsimile machine into
the system, the Clean and Simple interface being
...
... Grinnell Display grinnell() grinnell(device)
Note that the DCTs for the facsimile machine and
Grinnell display have been included in the
corresponding interface ...
... network.
For the time being, the UCL facsimile system is
directly attached to the various networks at the point
...
...
Let us consider an example. If a document is to be
read on the facsimile machine and the data stream
created ...
... created using a high-
resolution raster scanner, so that the original picture
can be reproduced faithfully. The facsimile data
represents binary images, in monochrome, with two
...
... unrealistic for storage or transmission.
Facsimile image data should therefore be compressed
to reduce its redundancy ...
... compression rate. CCITT 2-dimensional
compression and the DACOM facsimile machine use this
method.
...
... method.
It is desirable to integrate facsimile images with
other data types, such as text and geometric graphics ...
... graphics is a topic for the further study.
In the facsimile system, the following data
structures are supported. The corresponding
descriptions, if any, are listed as well and they can
...
... If a vector file is to be printed on the DACOM
facsimile machine, the image data should be re-
compressed into the DACOM-block format, the required
...
... vector.
For example, a facsimile page can be cleaned and then
printed on the facsimile machine. Note that the image ...
... For example, a facsimile page can be cleaned and then
printed on the facsimile machine. Note that the image
data must be recompressed before being sent to the
...
... image
data must be recompressed before being sent to the
facsimile machine. If the original data is the form of
DACOM block, it has to be decompressed as the
processing tasks only accept line vectors ...
... facsimile machine
w - print an image on facsimile machine
The descriptions of these processing tasks can be
...
... Suppose that an image file stored in a remote file
system is to be printed on the local facsimile machine.
Assume that the data is transmitted via the ARPANET
...
... before, since the delay caused by the network may
result in a time-out on the local facsimile machine,
the job should be divided into two subjobs.
...
... (1) The remote file is transmitted by using NIFTP
module. However, instead of being put on the
facsimile machine directly, the received data is
store in a temporary file.
...
... (2) The temporary file is read and the image is sent
to the facsimile machine for printing. Here it is
assumed the data received is in the form of DACOM
block so that no conversion is needed.
...
... COMSAT. At present DACOM block is the only format that
can be used as all the three participants in this
experiment possess DACOM facsimile machines and no
other data format is available in both ISI and COMSAT.
...
... data format is available in both ISI and COMSAT.
However, it is the intention of the ARPA-Facsimile
community to adopt the CCITT standard for future work.
As mentioned earlier, UCL already has this facility.
...
...
Above NIFTP, a simple protocol was used to control
the transmission of facsimile data. In this protocol,
the format of a facsimile data file was defined as
...
... the transmission of facsimile data. In this protocol,
the format of a facsimile data file was defined as
follows: Each DACOM block was recorded with a 2-byte
...
... header with the length-byte set to 2 and the code-byte
undefined. A facsimile data file could contain several
pages, which were separated by EOP blocks.
...
...
Though techniques for facsimile transmission were
invented in 1843, it was not until the recent years
that integration with computer communication systems
...
... in this note incarnates the compatibility and
flexibility of computerised facsimile systems.
In this system, facsimile ...
... facsimile systems.
In this system, facsimile no longer refers simply to
the transmission device, but rather to the function of
transferring hard copy from one place to another. Not
...
... Image is converted from one representation format to
another, so that different makes of facsimile machines
can communicate with each other. It is possible for a
picture to be presented on different bit ...
... Geometric graphics could also be included in the
system. Thus, the facsimile machine may serve as a
printer for multi-type documents. It is clear that
facsimile ...
... facsimile machine may serve as a
printer for multi-type documents. It is clear that
facsimile will play an important role in future
information processing system.
...
... following advantages can be recognised. Though our
discussion is concentrated on the facsimile system,
many features developed here apply equally well to
other information-processing systems.
...
... transmission. The data transfer is so slow that a
time-out may be caused on the facsimile machine. Though
this problem was solved by means of local buffering and
...
... required.
The facsimile system can be connected only to the
local network, the Cambridge Ring, while the foreign
...
... LSI MOS ever can or will.
(2) The facsimile service can be enhanced to be able
to support many users at a time.
...
... In fact the 44s and the LSI-11, to which the
facsimile machine and Grinnell display are attached,
are all connected to the UCL Cambridge Ring. A
distributed processing environment can be built up
...
... distributed system, the LSI-11 micro-
computer, together with the facsimile machine,
constitutes a totally passive facsimile ...
... facsimile machine,
constitutes a totally passive facsimile server
controlled by a UNIX user. A page is read on the
...
... controlled by a UNIX user. A page is read on the
facsimile machine and the image data stream produced is
...
... UNIX file and may be processed if
necessary. It can also be sent via the ring to the
facsimile server where it will be reprinted on the
facsimile machine.
...
... facsimile server where it will be reprinted on the
facsimile machine.
In order to build up such a distributed environment,
...
... UNIX, a set of high-level command is provided, while
the command strings for the facsimile station are
arranged automatically and they are totally hidden from
a UNIX ...
... higher-level, more sophisticated system which supports
a multi-type environment. In such a system, not only
does the facsimile machine work as an facsimile
input/output device ...
... a multi-type environment. In such a system, not only
does the facsimile machine work as an facsimile
input/output device, but it should also play the role ...
... In a future system, different services should be
supported, including viewdata, Teletex, facsimile,
graphics, slow-scan TV and speech. The techniques
...
... graphics, slow-scan TV and speech. The techniques
developed for facsimile will be generalised for use of
other bit-mapped image ...
...
To improve the performance of the facsimile system,
we are investigating how we could use an auxiliary
special purpose processor ...
... P. T. Kirstein, "The Role of Facsimile in Business Communication", INDRA Note 1047, Jan. 1981. ...
... T. Chang, "A Proposed Configuration of the Facsimile station", INDRA Note 922, May, 1980. ...
... T. Chang, "Data Structure and Procedures for Facsimile Signal Processing", INDRA Note 923, May, 1980. ...
... M. G. B. Ismail and R. J. Clarke, "A New Pre- Processing Techniques for Digital Facsimile Transmission", Dept. of Electronic Engineering, University of Technology, Loughborough. ...
... T. Chang, "Facsimile Data Compression by Predictive Encoding", INDRA Note No 978, May. 1980. ...
... T. Chang, "The Design and Implementation of a Computerised Facsimile System", INDRA Note No. 1184, Apr. 1981. ...
... T. Chang, "The Facsimile Editor", INDRA Note 1085, Apr. 1981. ...
... K. Jackson, "Facsimile Compression", Project Report, Dept. of Computer Science, UCL, June, 1981. ...
... CCITT, "Recommendation T.4, Standardisation of Group 3 Facsimile Apparatus for Document Transmission", Geneva, 1980. ...
... NAME
dacom - facsimile machine
SYNOPSIS
...
... DESCRIPTION
The DACOM facsimile machine can read a document, creating
the corresponding image data blocks. It can also accept the
...
... In this case, 74 byte DACOM blocks contaning correct CRC
fields are expected. On the other hand, character r is for
reading. In this case, a document is read on the facsimile
machine, the DACOM blocks being created.
...
...
This implementation of NIFTP is just a subset of the proto-
col as its main purpose is to provided the facsimile system
with a data transmission mechanism. For the sake of simpli-
city, only the necessary facilities are included in the
...
... special code (000000000001), known as EOL (End of Line),
follows each line of data. This code starts the facsimile
message phase, while the control phase is restored by a com-
bination of six contiguous EOLs (RTC). The data format ...
... bination of six contiguous EOLs (RTC). The data format of a
facsimile message is shown below.
start ...
... +---+------+---+------+-/
end of the facsimile data
|
v
...
... +----+--------+----+--------+-/
end of the facsimile data
|
v
...
... NAME
text - the text format for use in the facsimile system
DESCRIPTION
...
...
This is the representation structure for coded character
text. It is used in the facsimile system.
The text structure consists of a series of character
...