Abstract: The invention relates to a circuit arrangement for a video playback apparatus, comprising a band-pass filter arranged after the video heads in the luminance-signal playback channel. The frequency characteristic of the band-pass filter is variable in order to influence the amplitude characteristic of the FM sideband spectrum. The band-pass filter is followed by an FM demodulator and a crispening circuit. The frequency characteristic of the band-pass filter is controlled automatically depending on the level of the high-frequency components in the demodulated luminance signal in that the frequency characteristic of the band-pass filter is varied by means of a pre-emphasised luminance signal taken from the crispening circuit in such a way that a luminance signal whose FM spectrum in substantially amplitude-symmetrical relative to the FM carrier frequency is produced on the output of the band-pass filter.

Abstract: A circuit arrangement of input stages for a television tuner for the UHF, VHF and hyperband frequency bands in a continuous frequency range having primary bandpass filters for the UHF and VHF bands arranged in parallel, and connected to a signal input aerial (7). The input of the VHF primary bandpass filter is coupled to at least one grounded first inductance (27), series-arranged second and third inductances (29 and 31) between the output and the first inductance (27) and a grounded variable capacitor (33) arranged at the output and a first switch (35) which shunts the second inductance (29) and switches between the BI and the BIII ranges of the VHF band.

Abstract: The invention relates to a circuit arrangement for a tuner, particularly a television tuner, for a change over switching between two frequency bands with the aid of a switching diode, said frequency bands, particularly the VHF band and the hyperband, being filtered out by means of bandpass filters (1,7). The bandpass filters have at their inputs and outputs capacitance diodes for the purpose of tuning. The filtered signals are applied to a common tunable circuit (15) on the secondary side of the bandpass filters. The bandpass filter for the hyperband is constructed and dimensioned such that the signal is switched through by means of a switching diode (83) arranged at the low end of the bandpass filter (1). When this diode (83) is conducting a smaller output reactance, whereas in the case of a blocking switching diode (83), this bandpass filter (1) cuts off the signal and has a larger output reactance.

Abstract: The disclosed invention relates to a circuit arrangement for a tuner, particularly a television tuner, for changing over several frequency ranges filtered out by bandpass filters, particularly the hyperband and UHF band, by means of diodes connected to a common IF circuit which also serve as mixer diodes for mixing signals passed by the bandpass filters with signals generated by associated RF oscillators. The desired frequency range is switched on by switching on the associated RF oscillator so that the otherwise cut-off diode of this frequency range becomes periodically conducting.

Abstract: The invention relates to an automatic gain control circuit, preferably in magnetic recording and/or reproducing equipment, having a first input (1) and a second input (3). The impedance at output (5) of the automatic gain control circuit, when activated, is reduced to control the levels of the signals applied to the first input (1) and the second input (3), which impedance reduction in the case of actuation in response to signals applied to the first input is effected with a smaller time constant than in the case of actuation in response to signals applied to the second input. An audio signal without high frequency pre-emphasis is applied to the first input (1) and the same signal with high-frequency pre-emphasis is applied to the second input.

Abstract: A circuit is provided for frequency drift compensation of a tuning diode in tunable RF-circuits, and comprises a temperature-responsive voltage divider coupled between an independent voltage supply source and a reference potential, the tuning diode being coupled to a tap of the voltage divider. In this circuit the separate tuning voltage source is not loaded down and may thus produce a tuning voltage which is independent of the variation of the voltage from the temperature compensation portion of the circuit.