The controler of temperature and speed monitors the required operating condition of the fluid coupling contactlessly and requires no maintenance. Spraying and loss of operating fluid if the coupling overheats and the pollution of the environment associated with it can be avoided. In thecase of internal-gear drives the output speed (minimum value), in addition to the temperature, can be monitored. In this case the controler of temperature and speed cuts out immediately the output speed falls below its required value or the drive stops even before the coupling overheats. The controler of temperature and speed can be used on coupling and upward at peripheral speeds > 15 m/s. The transmitter is fitted to the coupling in place of the screw plug(fusible plug)