Abstract: Method and apparatus for processing compressed, stored analog signals, such as audio signals, from a storage medium, including first converting the signals to digital signals and thereafter expanding the signals.To realize a large volume range in the conversion of compressed recorded signals to expand digital signals, the compressed analog signals picked up from a storage medium are initially analog/digital converted and only then digitally expanded.

Abstract: To correct temperature caused changes in symmetry and gain in a voltage controlled amplifier including a logarithm circuit and an antilog circuit, an auxiliary voltage proportional to the absolute temperature is provided to control the antilog circuit; this auxiliary voltage is also contained as a factor in a voltage which controls both the logarithm and the antilog circuits.

Abstract: An amplifier for ground symmetrical signals includes a compressor at the input and an expander at the output, with the slope of at least one of its expansion or compression characteristics being adjustable for at least one half-wave polarity with the aid of an adjustment voltage. In order to reduce second order distortions at the amplifier output, a circuit is provided for determining the arithmetic mean value of the voltage across the amplifier output. A control value is produced from the determined mean value and the slope of the expansion or compression characteristic is regulated with this control value in the opposite direction so that the distortions are reduced.

Abstract: A circuit arrangement for coupling alternating voltage signals having frequencies within the audio frequency range between a low noise audio frequency source and a zero ohm amplifier, wherein the audio frequency source has a known source impedance. The circuit arrangement includes an output connected to the zero ohm amplifier and a highly resistant input for receiving the alternating voltage signals from the audio frequency source. The input is more resistant by at least one power of ten than the source impedance of the audio frequency source and the arrangement has a voltage amplification factor which is so low that no overshooting of the output signal will happen at the maximum occcurring voltage of the signals received at its input. The output of the arrangement is configured as a short-circuit resistant alternating current source which furnishes a maximum effective current of at least 10 mA.

Abstract: In a circuit for the automatic dynamic compression or expansion of a signal, the circuit presenting a useful signal path containing a first variable gain member which is electronically controllable for varying the transmission factor between the circuit input and output, a branch path connected at one point to the useful signal path and containing a control voltage generator for generating a control voltage from the signal at such point in the useful signal path, and a second variable gain member which is connected in the branch path and which is electronically controllable for varying the transmission factor exhibited by the branch path, with the transmission factor of the useful signal path being controlled to have a value dependent on the value of the control voltage and a counterregulation of the transmission factor of the branch path being effected relative to the transmission factor variation imparted to the useful signal path, the useful signal path includes a device causing the signal at one point alo

Abstract: In a circuit system for the generation of a direct control voltage dependent upon an alternating voltage for a dynamic compander device, the system including a charging capacitor, a charging circuit connected to charge the capacitor, and a circuit connected to discharge the capacitor, a comparator unit is connected to effect comparison between the alternating voltage and a reference voltage and to produce an output voltage representative of the amount by which the alternating voltage exceeds the reference voltage, and at least one of the circuits is formed of a current source and an electronically controllable current path connected between the source and the capacitor and having a control input connected to the comparator unit for varying the conductance of the current path as a function of the output voltage of the comparator unit.

Abstract: In a circuit for automatic dynamic compression or expansion the control voltage generator generates a control voltage which is linear against the logarithm of the input amplitude. This characteristic is achieved by a transfer member consisting of several transistors which are subject to different reference voltages and the series resistances of which are staggered.

Abstract: A variable gain alternating voltage amplifier having a d.c. negative feedback loop for setting the operating point of the amplifier wherein a change in gain of the amplifier is effected by a variable resistance feedback loop which is connected in parallel with the d.c. negative feedback loop and includes the series connection of a controllable resistor and a capacitor.

Abstract: A compander system is described, in which the `compression` and `expansion` modes are established by the selective use of a compression or expansion circuit as such or as a negative feed-back branch for a back-coupled amplifier.

Abstract: An amplifier circuit whose gain bears a desired relation to a control voltage, including a differential amplifier, a plurality of impedances interconnected between the amplifier terminals and switches interconnected with the impedances and switchable between two states which create two impedance configurations that give the circuit mutually complementary gain vs. control voltage control characteristics.

Abstract: In a circuit for the automatic dynamic compression or expansion of a signal between its input and its output, the circuit presenting a useful signal path connected between its input and its output and containing a setting member which is electronically controllable for varying the transmission factor between the circuit input and output, the circuit also presenting a branch path connected at one point to the useful signal path and containing a control voltage generator for generating, from the signal in the useful signal path, a control voltage applied to control the setting member, there is also provided a second setting member connected in the branch path and arranged to be electronically controllable for varying the transmission factor exhibited by the branch path, and means connecting the output of the control voltage generator to the second setting member for effecting a counterregulation of the transmission factor of the branch path, relative to the transmission factor variation imparted to the useful s