A variable attenuator includes active elements for providing the desired attenuation with good pulse response. Each of the transistors in the circuit is included in a current-splitting network which assures that the power dissipation remains the same, regardless of the attenuation setting.

Device for measuring frequencies, comprising a frequencymeter having a memory and digital outputs which programs an iterative frequency synthesizer. The latter comprises an interpolation oscillator switchable to a plurality of the decade units of the synthesizer. Means are provided for effecting a subtractive mixing of the synthesized frequency and the frequency to be measured and means are provided for controlling the frequency variation of the interpolation oscillator from the output of the mi...

An active memory for use in data processing apparatus for storing information data relating to a system defined by several parameters, each capable of taking a finite number of values, called situations. Each of these situations may be changed in value by a finite number of variations, called actions. For each parameter, a recording center is provided consisting of a matrix having two dimensions, one of which is allocated to the situations (i.e., the values of the parameters) and the other to th...

An active filter circuit. Two cascaded phase shift networks are in circuit with the non-inverting input terminal of an operational amplifier. A resistive feedback network couples the amplifier output back to the first of the phase shift networks. When an external input signal is applied to both phase shift networks and the inverting input terminal of the amplifier, the filter circuit has a pass band and a stop band. Inputs to any single one of these points selectably provide high-pass, low-pass ...

An improved high-pass or low-pass active filter section is provided by taking a standard active high-pass or low-pass filter section including an amplifier and adding thereto a single impedance between the input to the amplifier and the filter input. The addition of the single component increases the attenuation capabilities of the active filter section.

An active filtration system is described which may be particularly useful for filtering undesired harmonics of the fundamental AC frequency produced by AC to DC or DC to AC conversion. The filtration system of the invention produces currents of a phase, frequency and magnitude for injection into the AC system such that the undesired harmonic currents to be filtered sum with the injected currents giving a net zero current at the undesired harmonic frequency. The system can incorporate existing pa...

In an active equalizer for selectively boosting or attenuating predetermined frequencies of audio or other electrical signals, and which comprises an inverting amplifier having an inverting input which receives the input signal through an input resistance and an output connected with the inverting input through a feedback resistance and at which the equalized output is derived, and an active filter for determining the frequencies to be boosted or attenuated; there is further provided a change-ov...

An active aerial for use in car radios and aerial "arrays" comprising an aerial element and an aerial connected thereto. In order to obtain a low distortion and a good signal-to-noise ratio in spite of the presence of protection diodes to prevent overloading of the amplifier by atmospherics and in spite of contamination of the aerial etc, the input of the active portion of the amplifier is virtually grounded. To this end, the amplifier is preferably an operational amplifier having a high gain fa...

An active filter includes two differential amplifiers. The first amplifier has its inverting input connected to an input terminal of the active filter, its non-inverting input connected to ground through a resistor. A resistor and a capacitor are connected in parallel between the inverting input and output of the first amplifier. The second amplifier has its non-inverting input connected through a resistor to the output of the first differential amplifier and also through a capacitor to ground, ...

A liquid reactant comprising an amalgam of sodium, potassium or lithium w a small amount of water in a thin layer is provided over or in steel and like armor plate as a protection. It operates to effect embrittlement of the forward portions of projectiles which strike the armor through the layer, and thus to reduce penetration.