ABSTRACT
In modern, computer-based distributed automation systems, data communication between the individual system parts plays an important role. Transmission medium is the physical path between transmitters and receivers of a communication system. In a broadband system, to each communication channel two distinct carrier frequencies are allotted, one for each transmission direction; usually, a high-frequency for the forward transmission and a lower frequency for the reversed one. The central communication part of a distributed computer system is its system bus along which data is exchanged between the stations at the same or at different hierarchical levels. Data, collected in the field, can be transfered to the central computer at a transfer rate of 150 kbps. In modern distributed computer control systems, and especially in those applied as integrated information systems, local area network is definitely a central system part. It is generally accepted that data communication links represent the mandatory elements of distributed computers control systems.
