Heparin and polysaccharide(s) purificn

In a telecine chain, the scanning raster is rotated by applying a magnetic field perpendicular to the axis of the electron beam, and the distortion introduced by such rotation is compensated for. A rotate coil is located about the scanning tube the coil formed so that current passing through it induces the magnetic field and thus effects the rotation of the raster. The degree of rotation is within limits dependent on the current, and the direction of rotation is dependent on the direction of current flow. There is pref. an Absolute Angle Generator which has an input common with the input which controls the current through the Rotate Coil and which provides outputs for the compensation functions. Focus compensation is effected by applying a stimulus to the focus system which is based on the degree of rotation being effected.