The final controlling relay RKS-1 is meant for use in control, signalling and protection circuits as final controlling elements activated directly from a fibre-optic ST-type link. The relays are controlled with a ZP-6 software delivered along with our devices or may be controlled with software of other producers. A sample application of the relay may be steering of the acoustic signalisation panel used in MSA signalling system, placed away from the computer controlling stand.