A filter system for use in a three-phase slurry reactor is provided. Each heat pipe is configured to have a predetermined boiling point temperature selected according to design criteria. Further, it is preferred that the amount of the fatty acid monoester contained in the insulation liquid is in the range of 5 to 50 wt %. The track control module creates an object for each read document. Fine-tuning means responds to temporally consecutive first data patterns present in the data stream with a higher accuracy in order to perform a fine tuning of the oscillator on the basis of the temporal length between the two first data patterns and on the basis of the number of clock cycles of the controllable oscillator occurring in this temporal length.