Abstract: A low-noise bass-control device, which is digitally controllable in a simple manner, comprises an amplifier having an output connected to the series arrangement of a capacitor and a tapped resistor chain. The taps on said resistor chain are connected to an inverting input of the amplifier via a first switch and to the output of the control device via a second switch.

Abstract: A step-controlled attenuator circuit which, in order to avoid audible switching clicks in audio equipment, employs current-controlled switches. A switch is switched on by means of a gradually increasing control current and a switch to be switched off is turned off by means of a gradually decreasing control current.

Abstract: An electronic switch having an input and an output. Between the input and output a semiconductor junction is included which is switched by a transistor whose emitter electrode is connected to a terminal of the semiconductor junction which faces the input and whose base electrode is connected to a switching input. To reduce switching delays caused by stray capacitances on the inputs, a resistor is included between the connecting point of the emitter of the transistor and the semiconductor junction and the input, and the input is connected to a current source which is switched in synchronism with the transistor to provide a current such that the voltage swing produced across said resistor by said switched current source compensates for the voltage swing appearing on the emitter of the transistor during switching.

Abstract: The invention provides an improved class-B push-pull output stage comprising a first and a second output transistor of a first conductivity type, which stage is provided with a control loop for driving the second transistor in phase opposition as a function of the drive of the first transistor. Said control loop is adapted so that a stable quiescent-current setting is obtained and that the effect of poor high-frequency properties of a third transistor of a conductivity type opposite to the first conductivity type, which transistor is necessarily included in the control loop, is eliminated, so that a wide frequency range is obtained.

Abstract: An arrangement for the transmission of audio signals, comprising a delay line (1) provided with 5, 7 or 9 tappings situated at equal time intervals along the delay line. The tappings are each connected to a common adding circuit (16) via an amplitude control device (9 to 13). The ratios between the amplitudes of the output signals of the amplitude control devices, viewed from one end of the delay line (1) to the other end are 1:2n:2n.sup.2 :-2n:1 for five tappings, 1:2n:2n.sup.2 :n.sup.3 -n:-2n.sup.2 :2n:-1 for seven tappings, and 1:2n:2n.sup.2 :n.sup.3 -n:1/4(n.sup.4 -1)-2n.sup.2 :-(n.sup.3 -n):2n.sup.2 :-2n:1 for nine tappings. This yields an arrangement having a flat frequency response from the input (2) to the output (15). The invention also relates to a plurality of delay lines (for example 31 to 35) connected in series and to a reverberation unit provided with such a transmission arrangement.

Abstract: For the automatic calibration of an analog-to-digital converter an analog calibration quantity is measured and the digital signal is compared with a digital calibration signal associated with the calibration quantity. A digital difference signal is applied to a register for influencing its counting capacity, while the register contents of pulses counted during the measurement also represents one of the parameters involved in the analog-to-digital conversion. Because of the fully digital character of the calibration, this calibration can be performed very rapidly and accurately.

Abstract: An artificial reverberation device comprising first, second, third and fourth delay lines and first and second adder circuits with at least a part of said first, second, third and fourth delay lines connected in a cascade arrangement with the first and second adder circuits. First and second feedback circuits and first and second transmission paths are coupled to the cascade arrangement so as to produce a multiple reverberation effect with a minimum number of components.

Abstract: Artificial reverberation apparatus comprising a delay device (1) provided with a feedback circuit (5) and a feed-forward circuit (6) having a gain equal and opposite to that of the feedback circuit if the gain in the delay device is unity. In order to simulate a second echo having a different delay time using a minimum number of circuit components, the foregoing reverberation circuit is included in cascade with a second delay device (11) and the resulting combination is provided with its own feedback circuit (15) and feed-forward circuit (16). In order to simulate a third echo having yet another delay time, the resulting circuit may be included in cascade with a third delay device (21) with the resulting combination having its own feedback circuit (25 ) and feed forward circuit (26).

Abstract: A hybrid circuit comprising a current amplifier connected between the receive path and the transmission path of a four-wire transmission path, the common output of the current amplifier being connected to a two-way transmission path and the balancing impedance and an impedance transformer being provided between the other end of either the balancing impedance or the two-way transmission path, which results in a simple hybrid circuit.

Abstract: A Darlington transistor switch with a first and a second transistor, in which the base electrode of the first transistor is connected to the emitter electrode of the second transistor. In order to increase the switching speed of the device, the base-emitter capacitance of the second transistor relative to the base-emitter capacitance of the first transistor is increased so that voltage variations on the base of the second transistor with respect to the emitter of the first transistor are uniformly distributed over the base-emitter junctions of the two transistors.

Abstract: Attenuation arrangement comprising a step attenuator arranged in cascade with a controllable voltage divider via first and second voltage terminals, the step attenuator comprising a series arrangement of attenuation elements for dividing a voltage applied across said series arrangement into a plurality of voltage increments, which voltage increments are individually switchable between the two voltage terminals for varying the output voltage of the controllable voltage divider for the voltage range of the relevant voltage element, the direction of the polarity of the voltage between the two voltage terminals changing at a switch-over from one voltage increment to an adjacent voltage increment.

Abstract: Arrangement for protecting telephone lines and electronic circuits connected thereto from overvoltages. A first pair of diodes clamp the voltage of each wire versus the supply voltages in cooperation with a current limiting impedance. A second pair of (Zener-) diodes, separated from the first diode pair by means of a current limiting impedance, clamp the forward "transient" produced across the first diode pair versus the same or slightly different supply voltages.

Abstract: A supply circuit for a telephone subscriber's line circuit that includes a voltage source and a supply impedance connected in series with the line to the voltage source for limiting the line current upon short circuit of the line. The supply circuit includes an AC voltage generator, an AC/DC converter, and a circuit for coupling the AC voltage generator to the line via the supply impedance and the AC converter.

Abstract: A bridge circuit comprising an isolation transformer having six primary windings which are connected so that the voice currents do and the supply currents do not generate, for either direction of current flow, a resulting flux in the core of the transformer. The bridge comprises two transistor circuits which prevent the voice currents from flowing through a supply source connected to the bridge and also balance the bridge circuit so that the influence of longitudinal noise signals which are produced in a transmission line connected to the bridge circuit are suppressed. The direction of the feed current in the transmission line can be reversed by means of the transistor circuits.

Abstract: Delta modulation decoder comprising an integrating network provided with a first integrating capacitor which is on the one hand connected to an input terminal of the integrating network and on the other hand to ground potential through a second integrating capacitor. The 1-pulses and the 0-pulses of the delta modulation signal, applied to the decoder, are applied to a current source circuit generating a positive charging quantum in response to each 1-pulse and a negative charging quantum in response to each 0-pulse. Said charging quanta are applied to the input terminal of the integrating network through a correction network. This correction network is controlled by the voltage V.sub.C3 across the second integrating capacitor, so that, if V.sub.C3 is positive, the positive charging quanta are reduced and/or the negative charging quanta increased and that, if V.sub.C3 is negative, the positive charging quanta are increased and/or the negative charging quanta reduced.

Abstract: The line condition of a subscriber's line circuit supplied by an A.C. signal generator and an AC/DC converter is measured by means of a measuring resistor. The measuring resistor is inductively coupled to the supply circuit, which simplifies the measuring circuit.

Abstract: An analog-to-digital conversion circuit having a number of series-connected stages, each stage determining the difference between a signal current input and a reference current input, and at positive values of said difference transferring a current proportional to said difference to the succeeding stage. In each successive stage, the reference current is subtracted from the signal current until the residual current is smaller than the reference current. The number of successive stages in which this subtraction takes place can be detected to indicate the level of the input current.

Abstract: Interference insensitive line supervision circuit for subscriber's line having a given working range for the line potentials. A call can be simulated by the occurrence of overvoltages. Means are applied which supervise the occurrence of overvoltages. In the case of overvoltages these means produce control signals which result in that the state of a line state store cannot be affected by the line supervision circuit.

Abstract: A bridge circuit provided with an isolation transformer having four primary windings which are connected such that the voice currents do and the supply currents do not generate a resulting flux in the core of the transformer and which comprises two transistor circuits. These circuits on the one hand prevent the flow of voice currents via a supply source connected to the bridge and on the other hand balance the bridge circuit so that the influence of longitudinal noise signals which are produced in a transmission line connected to the bridge circuit are suppressed.