rfc809.txt
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INDRA Note 1185 INDRA
Feb. 1982 Working
Paper
RFC 809
UCL FACSIMILE SYSTEM
Tawei Chang
ABSTRACT: This note describes the features of
the computerised facsimile system
developed in the Department of
Computer Science at UCL. First its
functions are considered and the
related experimental work are
reported. Then the disciplines for
system design are discussed.
Finally, the implementation of the
system are described, while detailed
description are given as appendices.
Department of Computer Science
University College, London
NOTE: Figures 5 and 6 may be obtained by sending a request to
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UCL FACSIMILE SYSTEM INDRA Note 1185
Contents
1. INTRODUCTION...........................................1
2. SYSTEM FUNCTIONS.......................................2
2.1 Communication......................................4
2.2 Interworking with Other Equipment..................8
2.2.1 Facsimile machines............................8
2.2.2 Output Devices................................9
2.3 Image Enhancement..................................11
2.4 Image Editing......................................15
2.5 Integration with Other Data Types..................16
3. SYSTEM ARCHITECTURE....................................17
3.1 System Requirements................................17
3.2 Hierarchical Model.................................19
3.3 Clean and Simple Interface.........................20
3.3.1 Principles....................................21
3.3.2 Synchronisation and Desynchronisation.........21
3.3.3 Data Transfer.................................22
3.4 Control and Organisation of the Tasks..............22
3.4.1 Command Language..............................23
3.4.2 Task Controller...............................23
3.5 Interface Routines.................................26
3.5.1 Sharable Control Structure....................26
3.5.2 Buffer Management.............................27
4. UCL FACSIMILE SYSTEM...................................28
4.1 Multi-Task Structure...............................29
4.2 The Devices........................................29
4.3 The Networks.......................................30
4.4 File System........................................31
4.5 Data Structure.....................................32
4.6 Data Conversion....................................34
4.7 Image Manipulation.................................35
4.8 Data Transmission..................................39
5. CONCLUSION.............................................41
5.1 Summary............................................41
5.2 Problems...........................................42
5.3 Future Study.......................................46
UCL FACSIMILE SYSTEM INDRA Note 1185
Appendix I: Devices
Appendix II: Task Controller and Task Processes
Appendix III: Utility and Data Formats
Reference
1. INTRODUCTION
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
facsimile machines permit neither the storage of image
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
electronic communication services.
Integration of a facsimile service with computer
communication techniques can bring great improvements
in service. Not only is the reliability and efficiency
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
computer system make it possible to store large amounts
of facsimile data and retrieve them rapidly. Data
conversion allows 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 and graphics, to
construct a multi-media message, which can be widely
distributed over computer networks.
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 field. Some work has
been done to improve the facsimile service in several
areas.
(1) Adaptation of the facsimile machine for use with
computer networks. This permits more reliable and
accurate document transmission, as well as
improving the normal 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
transmitted at any time.
(3) Interworking with other facsimile machines. This
permits different makes of facsimile machines to
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UCL FACSIMILE SYSTEM INDRA Note 1185
exchange images.
(4) Compression of the facsimile images. This allows
more efficient transmission to be achieved.
Different compression schemes are investigated.
(5) Display of images on other devices. A colour
display is used so that the result of image
processing can be shown very vividly.
(6) Improvement of the images. The ability to 'clean'
the facsimile images not only allows for even
higher compression ratio, but also provide a
better result at the destination.
(7) Editing of facsimile pages. This includes the
ability to change pictures, alter the size of
images and merge two or more images, all
electronically.
(8) Integration of the facsimile 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 is
discussed. Finally, the implementation of the UCL
facsimile system is described. As appendices, detailed
description of the system are given, namely
I. Devices
II. Task controller and task processes
III. Utility routines and Data format
2. SYSTEM FUNCTIONS
The computerised facsimile system we have developed
is composed of an LSI-11 micro-computer running the MOS
operating system [14] with two AED62 floppy disk drives
[17], a Grinnell colour display [18], a DACOM facsimile
machine [16], and a VDU as the system console. This
LSI-11 is also attached to several networks, including
the ARPANET/SATNET [21], [22] and the UCL Cambridge
Ring. A schematic of the system is shown in Fig. 1.
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UCL FACSIMILE SYSTEM INDRA Note 1185
facsimile machine bit-map display
+------+ +------+
! ! ! !
+------+ +------+
+------+ \ / VDU
! disk ! +----------+ +-----+
+------+ ---- ! LSI-11 ! -- ! !
! disk ! +----------+ +-----+
+------+ |
+------+
! NI !
+------+
Network Interface
Fig. 1 Schematic of UCL facsimile system
In this system, a page is read on the facsimile
machine and the image data produced is stored on the
floppy disk. This data can be processed locally in the
micro-computer and then sent to a file store of a
remote computer across the computer network. At the
remote site, the image data may be processed and
printed on a facsimile machine.
On the other hand, we can receive image data which is
sent by a remote host on the network. This data can be
manipulated in the same way, including being printed on
the local machine.
Section 2.1 dicusses the problems concerned with
transmission of facsimile image data over a network,
while the following sections deal with those of local
manipulation of image data.
In order to interwork with other facsimile machine,
we have to convert the image data from one
representation format to another. Interworking with
other output devices requires that the image be scaled
to fit the dimension of the destination device. These
are described in section 2.2.
Being able to process the image by computer opens the
door to many possibilities. First, as considered in
section 2.3, an image can be enhanced, so that the
quality of the 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
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UCL FACSIMILE SYSTEM INDRA Note 1185
pictures. This is described in section 2.4.
In our system, coded character text can be converted
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 can be dealt with. This is discussed in
section 2.5.
2.1 Communication
The first goal of our computerised facsimile system
is to use a computer network to transmit data between
facsimile machines which are geographically separated.
Normally, facsimile machines are used in association
with telephone equipment, the data being sent along
telephone lines. Placing the facsimile machines on a
computer network presents a problem as the facsimile
machine does not have the ability to use a computer
network directly. To perform the network tasks a
computer is required, and so the first phase was to
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