Software requirements for automating a radiotelephone system

Abstract

Sentech is the common carrier signal distributor in South Africa for Television and Radio programs. This radio telephone system is used by the company as a communications link for voice and data between remote transmitter sites and the Transmitter Control Centre. The system was installed in 1986 and consists of a mixture of fixed bases and mobile units. The location of these transmitting sites is mainly on top of mountains in remote, sparsely populated areas. The use of cellular telephones for communication is impossible, as 80% of the sites fall outside the coverage area of the cells. Telkom infrastructure in these areas is most of the time not available or consists of shared farm lines. Only in the big metropolitan centres can data lines be considered at the main sites. It is not cost effective to consider it for the small sites. When the new system was installed, it replaced a single repeater system that relayed VHF radio signals from as far as 200 Km. The new system was a major improvement over the old system. Within a year it became apparent that it did not fulfill in all the needs of the company. A telephone-patch and two-tone cell call was added to increase the functionality. Data transfer and call-out systems were added to implement the new telemetry system to the sites. When the old handhelds became unreliable and the new units only use DTMF signalling, it became apparent that the system had to be upgraded.