Abstract: A fast slew rate automatic gain control circuit (10) includes a variable gain amplifier (14) which is responsive to a gain control signal and an amplitude detector (18) which produces an amplitude signal corresponding to the amplitude of the received signal transmitted through amplifier (14). The amplitude signal is provided to the input node of a loop filter (24) and to the inputs of threshold detectors (30, 32). Positive and negative slew threshold circuits (34, 38) provide threshold signals respectively for the threshold detector circuits (30, 32). When the amplitude signal is within the range of the threshold signals the loop filter produces the gain control as the function of the amplitude signal. When the amplitude signal is less than the positive slew threshold signal the threshold detector (32) produces a drive signal which is provided to the loop filter (24) and causes the generation of the gain control signal to have an accelerated positive slew rate which increases the gain.

Abstract: An A.G.C. circuit is disclosed having two modulators connected in series to modulate an input signal and an amplifier for amplifying the output of the second modulator and applying it to an output terminal. A detector detects the output of the amplifier and an integrator compares the detected level with a reference so as to produce a control signal dependent on the error. The control signal is applied to the first modulator through an impedance path having an impedance which decreases with increasing frequency, and is applied to the same modulator through an impedance path having an impedance which increases with increasing frequency. In this way, the first modulator performs modulation primarily dependent on the A.C. component of the control signal and a second modulator performs modulation primarily dependent on its D.C. components of the control signal.

Abstract: A circuit which allows for the simultaneous control of the bias voltages applied to the screen grids and control grids of output tubes while maintaining the ratio of said voltages, thereby providing a method for selectively varying a single plate characteristic (Power Output) of a tetrode/pentode vacuum tube.In the case of musical instrument amplifiers, it is a desirable effect to drive the power amplifier (output stage) beyond the point that said power amplifier is able to reproduce its input signal accurately, hence causing output distortion. Said point is known as the "Clipping Point".A clipping point is most usually achieved at high sound pressure levels which are uncomfortable and difficult to work under. By varying said voltages in the previously stated manner, one varies the clipping point accordingly, and therefore is able to obtain output distortion at variable sound pressure levels.

Abstract: A delayed AGC circuit in which an AGC detection output is divided into two portions, one of them is applied through buffer means to an IF amplification stage to thereby control the gain thereof, and the other portion is applied to a tuner through a threshold circuit to thereby control the gain thereof. A variable resistor or potentiometer for AGC delay adjustment and a high-frequency bypass device are connected at a point in the AGC signal path from the output of the buffer means to the IF amplification stage.

Abstract: An amplifier is disclosed for electrical signals which consists of a plurality of series-connected amplification stages each of which has at least one voltage-controlled amplifier element whose control characteristic can be adjusted by means of a control signal. An amplification is desirable for all individual stages which is equally great over an arbitrarily preselectable dynamic range. According to the invention, the amplifier has at least one control signal forming element for each of the amplifier elements of each amplification stage which exhibit different control characteristics compared to one another. This control signal forming element forms a secondary control voltage U.sub.ST2 from a primary control voltage U.sub.ST1 according to the equation U.sub.ST2 =m.multidot.U.sub.

Abstract: Apparatus for controlling the gains of a pair of gain-matched amplifiers includes means for applying to each amplifier a pilot tone in the form of an exponentially-decaying periodic signal. The apparatus also includes three control loops, one for comparing the output of one amplifier with a reference signal to derive an error signal used to control the amplifier gains when the pilot tone is absent, and a second for controlling the gains when the pilot tone is present. The third loop subtracts the outputs of the two amplifiers and uses the resulting error signal in conjunction with one or other of the signals from the other two loops to control the gain of one of the two amplifiers.

Abstract: An automatic gain control circuit having a coarse analog gain adjustment section producing discrete increments of db gain and a fine digital gain adjustment section. The digital section provides for adjustment of gain through a final increment of db gain to achieve precise gain setting. The output of the digital section is squared and compared to a reference signal to derive an error signal whose value is fed to an apparatus which iteratively determines the precise coarse increment and fine digital settings to achieve the final desired gain setting.

Abstract: An amplifier having a gain control terminal amplifies an input signal to produce an output signal of a desired magnitude. A gain control circuit coupled between the input and output signals and to the control terminal includes detectors of the input and output signal amplitudes. The control circuit further includes a first impedance network connected to the control terminal and a feedback circuit connected in series therewith, the feedback circuit including a second impedance network complementary to the first impedance network. A feedback signal of the feedback circuit is multiplied by the amplitude of the input signal and combined with the amplitude of the output signal and a reference signal at a summing point of the feedback circuit to maintain a response time of the control circuit which is essentially invariant with respect to the amplitude of the input signal.

Abstract: A circuit determines whether the signal transmitted by a variable-gain amplifier comprises information or not. If it comprises information, its level is regulated, by comparison with a first reference signal, in order to give a predetermined correct listening level at the output of the receiver. If it does not comprise any, its level is regulated, by comparison with a second reference signal, in order to give at the output of the receiver the listening level corresponding to the hearing threshold.

Abstract: An R.F. signal generator is arranged to provide an output signal having a controlled level, by means of a feedback loop into which an additional frequency dependent control signal is injected. This additional control signal is derived from a resistor network in which particular resistors, or combinations thereof, are selected in dependence on the output frequency of the signal generator.

Abstract: Complementary outputs of a differential amplifier are individually peak detected and the resulting signals are applied to the amplifier differential input in a manner to cause the output peak excursions to have substantially the same direct current levels. This causes the crossover of the two outputs to occur at the midpoint of the signal swing regardless of the input signal peak-to-peak swing, at whatever level.

Abstract: An adaptive signal weighting filter for use in a compander performs a frequency response weighting function so that during the encoding process the spectral region of dominant signal energy of the program signal is preemphasized with respect to other spectral regions and during the decoding process the corresponding spectral regions of the encoded signal are deemphasized with respect to one another in a complementary manner.

Abstract: A sensitivity control circuit is described for use with a sound movie camera having an automatic sound level control circuit. In one embodiment, the automatic sound level control circuit includes a pair of cascaded amplifiers whose overall gain is controlled by the conduction of an active control element. The active control element has an input terminal which receives a control signal representative of the amplitude of the signal output of the cascaded amplifiers. To desensitize the automatic sound level control circuit to background noise, a voltage source and a variable impedance element are serially coupled to the control terminal of the active control element to provide a control current for selectably varying the conduction of the active control element. The gain of the cascaded amplifiers is thereby selectively controlled and the sensitivity of the automatic sound level control circuit is reduced.

Abstract: In an environment of acoustic noise, such as a car radio playing in traffic or engine noise, both the volume (AGC) and dynamic range (Compression) of the audio amplifier are controlled by a local ambient acoustic noise sensor, such that gain is increased and dynamic range decreased simultaneously with increased ambient noise.

Abstract: A circuit arrangement for combining high frequency power components with the same frequency which come from amplifiers or generators and are fed to a 90.degree. parallel circuit bridge having two substantially decoupled inputs with the input resistance values of these inputs depending on the output load. The operating voltage supplies of the amplifiers or generators are separately controllable and are controlled so that the output powers of these amplifiers or generators, respectively, remain substantially constant even with mismatching.

Abstract: A directional power detector mounted between the power amplifier and antenna which supplies audio frequency output signals indicative of forward and reflected power, circuitry for summing and converting the output signals from the power detector means to a DC potential proportional to the magnitude thereof and a transistor connected in shunt at the input of the power amplifier and controlled by the DC potential for controlling the peak envelope power at the antenna.

Abstract: An echoscope for examination of objects with the aid of ultrasonic pulses, comprising at least one electroacoustic element for transmitting and receiving ultrasonic pulses during a transmission-reception period divided into n consecutive time intervals. The ultrasonic pulses are sent to the objects to be examined and are reflected therefrom. The echo signals supplied by the receiving element are amplified by an amplifier with time-dependent gain control. The gain control is brought about by a control voltage generator which supplies a control voltage to said amplifier for determining its signal gain as a function of time. Adjusting means for the control voltage generator are provided to make it possible to change the magnitude of the control voltage in the time intervals as a function of time. The apparatus also comprises a device for visually displaying the echo signals received during each transmission-reception period.

Abstract: A broadband automatic gain control amplifier is described incorporating a plurality of gain control loops, each responsive to signal levels at the output of the amplifier at different frequencies for developing a control signal to correct the output signal level simultaneously at that frequency and at other frequencies. Each of the gain control loops providing unique gain-frequency characteristic with respect to the other gain control loops.

Abstract: In a color television receiver, first and second amplifiers are respectively included in the luminance and chrominance channels to permit control of contrast and saturation. The amplifiers have gain versus control voltage characteristics including linear portions extrapolated to cut off at predetermined voltages which may or may not be the same. A first potentiometer is coupled between a source of fixed voltage equal to the extrapolated cut off voltage of the first amplifier and a gain controlling voltage source. The gain controlling voltage may be produced by a circuit including an element responsive to ambient light. The wiper of the first potentiometer is coupled to the first amplifier to couple a voltage developed at a predetermined point of the first potentiometer to the first amplifier to control its gain.

Abstract: A distortion measurement system for measuring distortion as low as 0.002% includes an ultra low distortion oscillator having a relatively fast response which is achieved by switching the time constant of the control loops of the oscillator during settling. The analyzer section included in the distortion system has a unique notch filter which provides low distortion. This is achieved by adding together two 90.degree. all pass phase shifters. In addition, automatic tuning is provided by two feedback control loops; one is responsive to out-of-phase signals which controls the RC filter circuits of the phase shifters and the other responds to the in-phase signals which controls the output summing junction of the notch filter. Finally, a feedforward type of simultaneous tuning is accomplished by ganging the oscillator frequency adjustment with the analyzer.