Developed and manufactured a fibre optic modem for high speed data transmission with dual redundant fibre interfaces. The modem featured extensive self testing mechanisms to detect a possible optical fibre or electronic failure before it occurs thereby preventing plant down time. The product needed to be extremely rugged, protected against dust ingress and capable of operating at elevated temperatures. Fifty units were manufactured for critical plant control applications in a steel mill.


  • Intel 80C196 based microprocessor hardware and firmware (in C and assembler).
  • Frequency division multiplexed FSK data + FM video modulation onto amplitude modulated light carriers.
  • HDLC synchronous data communications protocol.
  • RS232, 485, 422 data comms.
  • High speed USART design.
  • Extensive data error checking to ensure no lost data bytes.
  • FO emitter power control.
  • FO receiver signal level measurement.
  • ADC and DAC conversions.
  • Development of Cauer parameter LCR filters.
  • Measurement, calibration and display of temperature, power supply voltage, signal strengths.
  • Wide input voltage range power supply design.
  • Text based LCD display and keypad.
  • Design of custom aluminium extrusion and sand castings.