Abstract: A heat pipe roller includes a rotatable outer tube having a primary internal chamber for containing a fluid, a heater operable to heat the fluid and hence the tube, and a sensor. The sensor has a movable member which communicates with the primary chamber and is mounted on the tube for rotation therewith, and a fixed member situated in the region of the axis of rotation of the tube and so mounted relative to the tube that rotation of the tube does not rotate the fixed member. The fixed member is adapted to be connected to equipment for measuring an electrical characteristic of the sensor. The arrangement is such that, in use, the movable member moves in response to a temperature change or temperature related physical change in the primary chamber, thereby causing a corresponding change in the electrical characteristic of the sensor.

Abstract: The invention provides for deciding whether a recording dot is to be printed for the reproduction of scan dots. The scan dots being considered are complied in an input switching network into groups, for which an arithmetic processor determines the tonal value sum. The arithmetic processor emits a signal, if the tonal value sum exceeds a certain figure. The recording dot to be printed is determined by the presence of the signal in an output switching network. This process is performed successively for increasingly larger areas of the original, that is, for increasingly larger quantities of scan dots.

Abstract: The invention provides for deciding whether a recording dot is to be printed for the reproduction of scan dots. The scan dots being considered are compiled in an input switching network into groups, for which an arithmetic processor determines the tonal value sum. The arithmetic processor emits a signal, if the tonal value sum exceeds a certain figure. The recording dot to be printed is determined by the presence of the signal in an output switching network. This process is performed successively for increasingly larger areas of the original, that is, for increasingly larger quantities of scan dots.

Abstract: A process involving scanning an original linewise and determining the tonal value of each scan dot. Multiple scan dots are collected into a scan field. The average tonal value of each scan field is determined by averaging the tonal values of the scan dots of that scan field. The original is reproduced on a recording medium by individual recording dots that can take the tone value "print" or "no-print". Several recording dots correspond to a scan field of the original. The tone value of the scan field can be reproduced almost exactly on the average by printing a specific number of recording dots. The distribution of recording dots to be printed for a scan field is determined by subdivision of the scan field into the smallest subfields.