An improved switching means is provided in a loudspeaker system, which includes a power amplifier of direct coupled type having no output condensor to deliver an audio-frequency current to the loudspeaker, to eliminate undesirable effects by rapidly breaking an electrical connection between the power amplifier and the loudspeaker upon cutting off an a.c. power source. The switching means comprises circuitry having a remarkably short "time constant" compared with another circuitry provided outsid...

A logic gate circuit includes parallel drive of an output transistor and an inverter transistor by an input transistor. The inverter transistor then drives an active pull-up transistor which improves switching speed. The parallel drive of the invention allows the use of the active pull-up transistor without requiring a change in circuit voltage levels.

A D.C. tachometer circuit comprising a non-linear D.C. tachometer which produces an output voltage having an A.C. ripple, a first current path from the D.C. tachometer including means for removing the D.C. component of the output voltage of the tachometer, means for inverting and isolating the A.C. voltage ripple, and means for eliminating drift and the D.C. level of the inverted and isolated A.C. voltage-ripple, means for mixing the original output voltage of the D.C. tachometer including the A...

A zeroing circuit for use in conjunction with devices that produce output signals in response to input data signals feeds a compensating signal into such a device to produce a zero output signal when there is a zero input signal. The device being compensated is intermittently tested for the zero condition, and an aspect of the compensating signal is altered to produce the zero condition.

In an amplifying circuit having a plurality of amplifier stages which are DC-coupled, and in which an AGC voltage is applied to one of the earlier amplifier stages for providing an AGC operation; changes in the DC level of a later amplifier stage resulting from the AGC operation are detected, and such detected changes in the DC level are cancelled at the DC-coupling between the earlier and later amplifier stages.

Amplifier circuit having an input differential stage which has a first current mirror as the collector load. The output signal from this differential stage, which is transformed into an unbalanced signal by means of said current mirror, is amplified by means of a current amplifier and is supplied to the sum terminal of the first current mirror. This current mirror is connected to the input of a second current mirror the output of which supplies the output current of the amplifier circuit. For hi...

Circuit breaker having a movable contact mounted on a contact carrier. The movable contact is rivet-shaped having a large section which includes a surface for making contact with a stationary contact and having a shank. The shank extends through an opening in the contact carrier so that the large section of the contact is on one side of the contact carrier and a portion of the shank extends to the other side of the contact carrier. A flexible copper conductor is welded directly to the portion of...

Amplifier circuit having a gain which is adjustable by means of a control quantity. The circuit comprises a differential transistor pair the tail current of which is supplied by an input amplifier. The collector of one of the transistors of the differential part is connected in a negative-feedback sense to an input of the input amplifier, and the control quantity is applied as a differential voltage to the bases of the transistors of the differential pair.

An improved circuit-interrupter is provided having an improved operating mechanism for operating the separable contacts of the circuit-interrupter unit including a novel reverse-current loop structure enabling the separable contacts to be magnetically closed under higher contact pressure during the existance of high-fault conditions, and, on the other hand, when it is desired to open the separable contacts of the improved circuit-interrupter under heavy-fault conditions with the contacts welded ...

The amplitude is detected of both the input and output signals of the circuit (such as an audio amplifier) it is desired to protect. When, for example, a short circuit occurs across the load being driven, there is a sudden change in the ratio of these amplitudes and in response to this change, the signal to the output driver stage of the circuit is shunted to ground.