Abstract: There is provided a magnetic bearing drive circuit driven from a pair of Direct Current (DC) link voltage rails, said magnetic bearing drive circuit having at least one amplifier providing an output PWM drive signal for driving a magnetic bearing winding, said output PWM drive signal being provided to the magnetic bearing winding through a plurality of drive signal rails, said magnetic bearing drive circuit comprising a pair of voltage offset devices coupled to the DC link voltage rails and arranged to provide a pair of offset catcher voltage rails from the DC link voltage rails, and primary clamping means coupled between each offset catcher voltage rail and a respective one of the drive signal rails.

Abstract: There is provided a magnetic bearing drive circuit driven from a pair of Direct Current (DC) link voltage rails, said magnetic bearing drive circuit having at least one amplifier providing an output PWM drive signal for driving a magnetic bearing winding, said output PWM drive signal being provided to the magnetic bearing winding through a plurality of drive signal rails, said magnetic bearing drive circuit comprising a pair of voltage offset devices coupled to the DC link voltage rails and arranged to provide a pair of offset catcher voltage rails from the DC link voltage rails, and primary clamping means coupled between each off-set catcher voltage rail and a respective one of the drive signal rails.

Abstract: A receiver for orthogonal frequency division multiplexed signals includes means (14) for calculating the (discrete) Fourier Transform of the received signal, and means (20) for calculating the phase error due to local oscillator errors.

Abstract: Sequential/interlace scan conversion of NTSC or PAL color television signals is effected by an encoder the output of which is connected to the input of scan conversion apparatus. Controllable phase shift means is included in either the color signal input or the subcarrier input of the encoder and is adapted to vary the phase of the modulated subcarrier for each line of the received color signal by an essentially integral number of quarter cycles in dependence upon the line number. The control is such that the conversion apparatus provides an encoded output signal with the color subcarrier in PAL or NTSC format. The invention can also be used in converting between different types of interlace systems.