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 Ann Westine at USC-Information Sciences Institute, 4676 Admiralty Way, Marina del Rey, California, 90291 (or WESTINE@ISIF) including 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 RFC809a.FAX and 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 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 machine on the other end of a telephone wire. Because of the property of the DACOM 6450 used in the experiment [16], the interface could be identical to one developed for connecting to an X25 network. The binary synchronous mode of the chip used (SMC COM5025) was appropriate to drive the DACOM machine. At the other side of the computer network there was a similar computer with an identical facsimile machine. The problem of transmitting a facsimile picture now appeared simple: data was taken from the facsimile machine into the computer, transmitted over the 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 - 4 - UCL FACSIMILE SYSTEM INDRA Note 1185 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. facsimile machine +---+ interface ! ! +--+ +-----+ ! ! == ! ! == ! ! computer +---+ +--+ +-----+ | - - - - - - computer / \ network \ / facsimile - - - - - - machine | interface +---+ +-----+ +--+ ! ! computer ! ! == ! ! == ! ! +-----+ +--+ +---+ Fig. 2 Facsimile transfer system The experimental system was used to perform a joint experiment between UCL and two groups in the United States. Pictures were exchanged via the ARPANET/SATNET [21], [22] between UCL in London, ISI in Los Angeles, and COMSAT in Washington D.C. (Fig. 3). This environment was chosen because no equivalent group was available in the UK. One problem concerned with such image data 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 characters - or over a dozen typed pages. Thus for a given number of pages put into the system, an immense amount of computer data is produced. This means that the transmission will be slower than for sending text, and that far more storage will be required to hold the data. Another problem was encountered which became only too apparent when we implemented this system. The network we were using was often unable to keep up with the speed of the facsimile machine. When this happened the - 5 - UCL FACSIMILE SYSTEM INDRA Note 1185 US UK satellite COMSAT __ +---+ +--+ / \ ! ! -- ! ! / \