Abstract: The invention relates to a method and arrangement for reducing to a minimum the electrical alternating fields generated in the surroundings of a visual display unit (1). The visual display unit includes a voltage connected part (5), on which undesirable voltage variations occur. A smoothing high voltage capacitor (C3) of high capacitance is connected to the voltage connected part (5). Connected between the high voltage capacitor (C3) and earth is a compensating circuit (20) which functions as a negative capacitor whose capacitance is greater than the capacitance of the high voltage capacitor (C3) by a given factor.

Abstract: A cathode ray tube (3) (CRT) has a deflecting coil (1) surrounded by a funnel-like casing (4) of magnetic material. The deflecting coil generates a magnetic deflecting field (B) for the electron beam and a magnetic leakage field (BL) in the CRT environment. The leakage field is composed of a dipole field and a quadrupole field. To reduce the magnetic field strength in the CRT environment a magnetic compensation field which is counterdirected to the leakage field is generated. The compensation field is composed of a dipole field which is generated by a first compensation loop (7) and a quadrupole field which is generated by a second compensation loop (9). The first compensation loop (7) is substantially flat and at right angles to the magnetic deflecting field (B). The second compensation loop (9) is flat and at right angles to the longitudinal symmetrical axis (z) of the CRT and has an upper (9a) and a lower (9b) part which generate two mutually opposing dipole fields (DK2,DK3).

Abstract: A focus alignment system for X-ray photography devices is provided for use with such devices where the film holder is independent of the X-ray source. The X-ray source has associated therewith two light beam projectors. The beam of one light projector is aligned with the X-ray beam while the beam of the other projector is at an angle thereto. The X-ray beam focus to film distance is correctly set when the light beams intersect on the surface of the film holder. Markings on the film holder indicate central positioning of the X-ray beam when the one light beam is aligned with the markings.