Data and text communication today and tomorrow

Abstract

The qualitative development of the telecommunication technology may overtake its quantitative progress due to the fact that the growth and diversification of telecommunication services can be observed primarily in data and text communication, shortly in nonvoice communication areas. The major conditions of this kind of progress are proper technical level of service providers, reception capability of users and marketing actions to match the previous two. Traditional text communication service, the telex (see paper by Troll. J.) does have some innovative reserves in it for an environment where they can be utilized optimally. It is fast and highly effective (especially if its restrictions do not cause additional problems), and its interactive capabitities can be some-limes well exploited. A stored-program-controlled and computer-device-equlpped telex system supple-mented with message recording and other special services and, where appropriate, co-operating with other telematics systems described below, wiil be for long a primary element of telecommunication services in Hungary, especially in the category of cheap terminal equipment.
The first data transmission applications in Hungary were also based on switched-line and leased-line telephone networks. They provide for the majority of data transmission even today (see paper by Verebélyi, A.). There existed a line-switched network in Hungary for data transmission of only 200 baud rate in the period of 1971 - 1980. Since 1981, our national line-switched network is available at rates of 300 baud, but also at 2400 and 4800 bit/s. Recently, in 1991, the 9600 bit/s category was added, and all can be used as direct leased-line network in non-switched mode. In the switched-line mode, the proper dialing procedure should be selected from existing options accordlng to the given network, to the desired application and to the mode of dialing. In analogue circuits, digital signals can be transmitted effectively via modems, many of them operate under microprocessor control for simple use and reliable operation, and for superior performance. Until the analogue circuits exist, modems will be needed for data transmission, and the quallty enhancement and convenience-oriented services of modems provide a good development prospect for data transmission using line-switched telephone networks. In the more distant future, however, the integration following signal digitalization (ISDN services) will cause digital line-switched network services to take the role of analogue networks.
The history of packet-switched data services in Hungary is very short. Its element and tools are described in the paper by Gonda, L., coverlng dial-in and dial-out gateway functions needed for the full exploltation of the advantages of packet switching (rate adaptation, packetizing and depacketizing for non-packet-switched terminal communication etc). The most important element of dial-in to packet-switched network through line-switched circuit is the identification as prescribed in the CCITT X.32 recommendation. The use of public packet-switched networks in Hungary started with the Information Infrastructure Development project called IIF. Alter its introduction, X.25 type data transmission services have been established in several private networks, too. Therefore, access conditions, call numbering system, tarifs are presented to some details. Telematics services have grown rapidly in Hungary (see papers by Szabó. K. and Balogh. S.). The most popular of them is telefacsimile. Its worldwide use has been reflected also in Hungary, despite the deficlences of our telephone network. The flexibility and capabilities of the telefax have developed continuously. Earller, systems based in scanning only were used, but now many computer-controlled systems exist with error correction and data compresslon capabilities. Telefax stations have been connected to the telephone network rather than establishing its own network. Therefore, the new component of telephone sets is a selector device sensing wether an incoming call is telephone or fax call.
The telematics services for the most extensive utilization are expected to be message handling and bulletin board systems. The first realization of such services in Hungary is the MINITEX (see paper by Berkes, J) which is capable both for message handling and for cooperation management of telex and teletex. However, as the base service, it could con-nect only minitex type devices to the telephone network. Its major benefit is the portability. Presently the most complex device in the telematics field is the teletex (Berkes, J.) because it can be adapted readily to international protocols for Open Systems Interconnection architecture. Standard terms of message handling (Berkes, J.) have been specified by common ISO and CCITT specifications (using MOTIS and MHS marking, and for CCITT, in the series of recommendations X- 400). Because of the complexity of their description and realization programs, the presentation here gives only a brief overview.
The most interesting and "colourful" representative of telematics services is the videotex. It needs a special extensive marketing or, to become an economically reasonable service, a management similar to that of the French approach. The paper by Jurenka, 0. presents the main characteristics, components and procedures of videotex operations. Several videotex systems are now operational in Hungary but partly under technical conditions and parameters which are not compatible with each other. The role of the public network operators can be to establish a common platform for videotex compatiblllty or cooperative regime as well as to make videotex systems or other countries available for Hungarian users. For such a perspective, however, Hungarian systems are unappropriate presently but the possibility of the development toward this purpose might be feasible.