An investigation of an SDLC-based remote monitoring and control system

There is a large and increasing demand for remote monitoring and control systems in such applications as pipelines, reservoir systems, sewerage systems and shopping centres, where there are numerous inputs and outputs spread over a large physical area. To monitor and control these inputs and outputs, at a local level, devices known as outstations are used. The outstations are, in turn, controlled by a centralised master station. The purpose of this paper is to investigate the use of the SDLC protocol for controlling the flow of data around such a system. The SDLC protocol is a modern bit-oriented protocol which offers an efficient method for ordering the flow of data around a communication system, As the SDLC protocol places no restrictions on the length or content of the messages sent over the communications link, it offers a very convenient method of communication. It also offers a comprehensive method of detecting any errors that may occur in the communication link, which is of vital importance in any control system. An SDLC software package is described which makes communication between stations extremely easy and reliable. Many applications of remote monitoring and control may now be envisaged, such as factory automation. To take advantage of these new applications, a cheap out-station with built-in modem was designed and constructed. The use of the SDLC software package in hostile environments has been made possible by the introduction of Hamming error-correcting codes. This also widens the number of possible applications for which the SDLC software package may be used,