The single- or dual-channel devices of the FOC family transmit fieldbus protocols such as Profibus-DP or Modbus RTU as light pulses via fibre optic cables. Unique on the market are the two Ex variants of the FOC couplers, which can be mounted in zone 1 and transmit intrinsically safe signals according to RS485IS. With the FOC media converters, large transmission distances can be overcome; depending on the fibre optic cable used, distances of over 2,500 metres are possible. Fibre optics are also immune to electromagnetic interference. For high availability, users can map ring topologies as well as point-to-point with the devices. All units have a universal shielding concept that can be easily adapted to the respective method used. Detected faults are reported via the fault message output of the FOC converters, which speeds up troubleshooting enormously.