Abstract: With a muting device according to this invention, an input signal is supplied to a changeover switch, which in turn is connected to an output terminal through an amplifier and muting switching circuit. A terminal from which a switching operation changeover signal is sent forth is connected to a changeover switch, and also to a muting control circuit through a differentiation circuit. The output terminal of the muting control circuit is connected to a muting switching circuit. The differentiation circuit is formed of a series circuit of a resistor and a capacitor. A junction between the differentiation circuit and muting control circuit is connected to a constant input terminal through a resistor. The muting control circuit is provided with a single input terminal.

Abstract: An automatic gain control circuit comprising a gain-controlled amplifier for receiving a variable amplitude, pulse-type input signal to produce a substantially constant amplitude, pulse-type output signal which is applied to a feedback circuit for comparison with a predetermined reference voltage to generate a control voltage to set the gain of the amplifier. A voltage limiter included in the feedback circuit clips the pulse peaks of the output signal whenever the peaks exceed a predetermined amplitude so that the gain of the amplifier is reduced in a prescribed manner to preclude output signal dropout. A peak detector and a filter included in the feedback circuit are capable of operating in fast and slow modes. When operating in the fast mode, the peak detector responds essentially to each pulse peak of the output signal and the filter has a wide bandwidth so that the automatic gain control circuit operates with a prescribed fast time response.

Abstract: An audio processing system for maximizing the efficiency of transferring audio frequency signals. Signals to be processed are supplied to a bandpass input filter, then to a primary active frequency control. Its output drives a primary voltage compressor selectively limiting audio dynamics to a predetermined window, the latter being controllably preset and driven with different audio bands of amplitude determined by the primary frequency control to maximum compression levels indicated by a visual indicator. The output of the primary compressor is presented to a secondary active frequency control driving a secondary dynamic compressor with different audio bands. A second visual indicator indicates maximum compression levels of the latter. An automatic gain control (AGC) tied to the secondary compressor supplies feedback to the primary voltage compressor via AGC circuitry to control primary compression as a function of average, overall dynamic compression of the system.

Abstract: An AC coupled amplifier system is protected from overloading input signals by means of a "bootstrap" circuit which provides a compensation signal substantially matching the overscale portion of such input signal and applies that compensation signal to the coupling capacitor as an offset in order to prevent excessive charge accumulation on that capacitor. A voltage controlled current source serves as a signal range limiter in the circuit and responds to overscale input signals by causing a circuit loop opening and forcing loop closure in a secondary feedback circuit from which the extent of input signal overscale is determined. The matching compensation signal is then derived from such determination. The protection circuit further provides a reset function to account for extended overscale input signal levels.

Abstract: An amplifier system with automatic distortion control including an amplifier provided with a detector between the amplifier output and feedback ports for detecting a nonlinear condition with a balanced differential circuit connected to the detector and feeding a full wave threshold detector which charges a storage capacitor proportionally to the percent clipping of the output signal of the amplifier. The storage capacitor is discharged into an input variable gain amplifier in the amplifier input circuit to reduce the gain for minimizing clipping.

Abstract: In a circuit for the generation of a direct control voltage dependent upon an alternating voltage the changing of the control voltage is delayed after a rapid decrease in the alternating voltage amplitude. This delay time is controllable in dependence upon the time difference between an increase and a rapid decrease of the alternating voltage amplitude.

Abstract: In an automatic gain control circuit specifically adapted to control the gain of an amplifier for operating a noise cancelling circuit, a detector is provided for detecting a detector input signal, such as detected noise pulses. The detector includes a differential amplifier comprising a transistor pair connected to a constant current source. According to the detector input signal level, the constant current is switched between the transistor pair. The normally off transistor of the pair is connected to a third transistor, through which a substantially invariant current flows to relatively slowly charge a capacitor in a time constant circuit when the input signal level exceeds a reference level given by the difference between a pair of bias voltages for the transistor pair. The voltage accumulated across the capacitor serves as an automatic gain control signal, which rapidly disappears when the input signal level decreases below the reference level.

Abstract: An automatic gain control circuit includes a VCA, an AGC detector and an AGC time constant circuit which form an AGC loop. The AGC circuit further includes a level detector and a time constant designator. When the level detector detects an excess level of a signal derived from the VCA, the designator changes the time constant of the time constant circuit.

Abstract: In a circuit which matches the speaker input signal in a car radio to the then-present noise level, an additional RC circuit is interconnected between the speaker input terminal and the input of the volume control element. Sudden increases in the speaker input voltage following a modulation pause which cause a high increase in the gain of the volume control circuit will counteract this gain, thereby preventing the excessive increase in speaker sound output following such a modulation pause which took place in the known circuits. Zener diodes to limit the voltage at the volume control elements in dependence upon the battery output voltage and to a value such that the output stage driving the speaker will not be overdriven are also provided.

Abstract: To minimize overmodulation in an active window antenna and radio receiver system, an amplification control voltage is produced in the active antenna, i.e., directly behind the antenna pre-amplifier, and is used to control the amplification of the pre-amplifier.

Abstract: A circuit which provides a control signal to dynamically adjust the level of clipping for an audio signal is described. The criterion for allowable clipping employed by the circuit is whether the clipper induced distortion is noticeable; the clipper induced distortion may be audible, however, remain unnoticeable. A frequency weighted correlation is performed on the audio signal to evaluate the waveform and establish an unnoticeable level of clipping.

Abstract: Signals carried over a multiplexed transmission medium between first and second stations suffer transmission losses such that the signal one station generates has a substantially greater magnitude than the signal it receives from the other station. A differential amplifier is utilized to extract and amplify the weaker signal thereby establishing signal balance. Following the differential amplifier is an automatic gain control stage which includes novel sample and hold and activity checker circuitry. The activity checker responds to the frequency of input signals to either allow variable gain control action or, when the frequency is representative of noise, to hold the gain control at its instantaneous value prior to the onset of noise.

Abstract: A regulation device for controlling the level of a signal having a controllable amplification, the signal fluctuating in amplitude, includes a signal control device, first and second threshold stages postcoupled to the signal control device having first and second thresholds, respectively, which thresholds define a predetermined signal range, and an element chargeable and dischargeable to first and second potentials, respectively, postcoupled to the threshold device, and connected by feedback to the signal control device for controlling its amplification within the predetermined range.

Abstract: An improved signal expansion system and technique is disclosed. The system comprises a detector for sensing an input signal and for producing responsively thereto a D.C. control signal having an amplitude as a function of the input signal, and a gain control amplifier for amplifying the input signal, the amplifier including means for controlling the gain of the amplifier as a function of the amplitude of the control signal. The improvement comprises means for varying the amplitude of the D.C. signal at least in part as a function of the time derivative of that amplitude.

Abstract: The invention relates to a circuit arrangement for adjusting the volume of an automobile radio receiver in dependence on road noise, comprising a microphone which picks up the noise and emits an electric signal which is conducted by way of an amplifier, a rectifier and a time-controlled circuit, to a control-adjustment member contained in the low frequency channel of the receiver.

Abstract: An AC input signal and a DC supply voltage are applied to a tapped coil having end points from which differential input signals are coupled to a differential variolosser that controls the gain of cascaded differential amplifiers. The two output terminals of the cascaded amplifiers are electrically connected together through a pair of equal valued resistors to provide a DC reference voltage at the junction of the two resistors, where the AC signals cancel. The reference voltage is coupled to one side of a high-gain differential control amplifier and to both sides of a differential half-wave rectifier circuit. One side of the rectifier is also connected to one output of the cascaded amplifiers for detecting an amplified signal there. The detected signal is integrated and coupled to the other side of the control amplifier to produce the control signal which regulates the drive current to and loss presented by the variolosser, and thus the level of the input signals to the cascaded amplifiers.

Abstract: A sound motion picture camera with sound recording equipment rendering it possible to record sound accompaniments by way of a magnetic track on the picture film and provided with an automatic gain control circuit operating with attack and recovery times automatically controlled in accordance with variation of the dynamic range of the sound accompaniment.

Abstract: An automatic gain control amplifier having a controlled recovery of gain is disclosed and includes a peak detector for generating an output when the amplifier output exceeds a predetermined level, a memory setting circuit responsive to the peak detector output, a memory controlled by the memory setting circuit, and a memory adjust circuit responsive to information derived from the amplifier output. The output of the memory controls an attenuator of the automatic gain control amplifier. Amplifier output level change detection circuitry is also disclosed and accepts the output of the amplifier for producing an output indicating amplifier output level changes exceeding a predetermined magnitude. The level change detection output controls the memory adjust circuit.

Abstract: A circuit for providing adaptive level control in a sound-recording device. A feed-back signal drives a variable attenuator which controls the input level to the audio amplifier stage. Means are provided for preventing voltage spikes at turn-on from adversely affecting the operation of the attenuator and which provide stable sensitivity control.

Abstract: An improved circuit for producing a signal indicative of an input signal floor level is disclosed for use in determining the noise level of an audio signal in a receiver voting system. An input audio signal which contains noise is amplified by variable gain amplifier circuitry consisting of a constant gain amplifier and a variable attenuator. Detector circuitry then develops a signal which is indicative of the noise level, this signal substantially corresponding to the minimum peak magnitude of the amplified input audio signal. During pauses between audio tones in the input audio signal, this minimum signal magnitude coincides the residual background noise level of the input audio signal. Control circuitry couples the noise level indicative signal to the variable attenuator and constitutes a negative feedback loop for inversely and nonlinearly varying the amplification of the input signal in response to the magnitude of the noise indicative signal.

Abstract: A gain control circuit is connected between an output terminal of a transistor detector circuit for audio-frequency or voice signal and an audio amplifier circuit. The gain control circuit comprises a control transistor having an output electrode at which an output potential is produced which is lowered correspondingly as the potential at the output electrode of the detection transistor is decreased, and is utilized for controlling the gain of the audio amplifier circuit. The gain control circuit further comprises time constant circuit, for controlling the control time and the restoring time of the potentials at the output electrodes of the above two transistors and a switching circuit.