Abstract: A circuit measures the beam current of a cathode ray tube and derives a control signal from it to prevent overdriving and defocussing of the CRT. The circuit can measure both peak and average values and has an isolation circuit, such as an emitter follower, to prevent loading of the cathode circuit of the CRT.

Abstract: A circuit arrangement in a picture display apparatus including an integrator having a time constant which is of the same order as one field period and which integrates the control voltage generated by the line phase discriminator. The voltage thus integrated is applied by means of a switch to the output terminal of the discriminator during each field blanking period. As a result both the flickering effect and the shift which may occur at the upper edge of the screen of the picture display tube as a result of the broad field synchronizing pulses and the equalizing pulses disappear. The circuit arrangement also includes a circuit which separates the discriminator from the integrator and which may be constituted as a long-tailed pair arrangement.