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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      your name and postal mailing address.  Please mention that you are
      requesting figures 5 and 6 from RFC 809.


      OR: You can obtain these two figures online from the files

          <NETINFO>RFC809a.FAX   and   <NETINFO>RFC809b.FAX

      from the SRI-NIC online library.  These files are in the format
      described in RFC 769.


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



                              - 1 -

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.






                              - 2 -

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




                              - 3 -

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
     attach the facsimile machine to a computer.

       The facsimile machine is not like a standard piece of
     computer  equipment.  We  required  a  special 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