Abstract: A variable-frequency main oscillator of digitally tunable high output frequency f.sub.A is controlled by the integrated output voltage of a phase discriminator receiving on the one hand a relatively low comparison frequency and on the other hand a matching feedback frequency stepped down from output frequency f.sub.A by frequency division or by heterodyning with an auxiliary frequency f.sub.H of the same order of magnitude from an ancillary oscillator, a difference frequency f.sub.D =f.sub.A -f.sub.H is fed to a frequency discriminator delivering a corrective voltage, independent of that emitted by the phase discriminator through a filter network, to the control input of the main oscillator. A pair of frequency selectors varying the feedback frequency and/or the comparison frequency enable the output frequency f.sub.A to be adjusted in coarse and fine tuning steps, the coarse adjustments being also applied to the auxiliary frequency f.sub.H to limit the excursions of the difference frequency f.sub.D.

Abstract: A test object, such as a communication path used for data transmission, is examined by applying to its input a measuring signal M consisting of several simultaneously or sequentially generated test frequencies which may be harmonically interrelated, extracting from the output of the test object a distorted version E of the measuring signal, locally generating a compensation signal K with frequency components matching respective test frequencies, and subtracting the two signals E and K from each other to obtain a residual signal R=E-K. The compensation signal K is produced by one or more local oscillators and as many frequency converters under the control of regenerating circuitry which locks each of its components in phase and amplitude to the corresponding test frequency. Regeneration takes place in a different frequency range to which the residual signal R is transposed and from which the compensation signal K is retransposed with the aid of a locally generated carrier.

Abstract: A manually operated direct-current generator, with an output voltage whose polarity and magnitude depend on the direction and speed of rotation of a control knob, charges a storage capacitor in an input circuit of an operational amplifier which works into two comparators respectively responsive to positive and negative voltages exceeding selected thresholds. A triggerable pulse source, upon actuation by either comparator, feeds back one or more discharge pulses to the storage capacitor and also steps a reversible pulse counter in either a forward or a reverse sense.

Abstract: A frequency generator of the digitally settable type comprises several voltage-controlled oscillators, specifically a pair of pilot oscillators and a final oscillator, provided with respective phase-locking loops each including a phase discriminator. The loops of the pilot oscillators further include respective frequency dividers whose step-down ratios are controlled by setting commands stored in associated memories which can be reloaded, under the control of manually or automatically adjustable selectors, only in the presence of an enabling pulse generated by a coincidence circuit with inputs connected to the outputs of a source of reference frequency and of the several stages of a chain of binary dividers connected to that source, certain of these stage outputs delivering comparison frequencies to the phase discriminators fed by the frequency dividers of the pilot oscillators.

Abstract: The average amplitude of an incoming signal voltage of variable frequency is measured by half-wave rectification of that signal voltage to produce a pulsating current which is subtracted from a continuous current in the input of an integrating amplifier. The fluctuating output voltage of this amplifier is periodically sampled, once per cycle of the signal voltage, to provide a train of corrective pulses. These pulses are accumulated to provide a reference voltage fed to a differential amplifier which controls the continuous current in response to differences between this reference voltage and a feedback voltage proportional to that current to compensate for changes in average signal amplitude. The magnitude of the continuous current, read by a meter, is therefore a measure of the desired amplitude. The voltage samples may be weighted, in proportion to signal frequency, by a variable-gain amplifier or a sampling switch closed for different periods in the output of the integrating amplifier referred to.

Abstract: A digitally settable frequency generator comprises a master oscillator whose operating frequency f.sub.Q is variable between a normal value f.sub.Q " and a slightly lower value f.sub.Q ' = (1-p)f.sub.Q " with the aid of a normally disconnected tuning capacitor. The master oscillator works into a frequency divider of fixed step-down ratio m:1 (or 2m:1) to produce a reference frequency f.sub.B. A slave oscillator, generating an output frequency f.sub.A = gf.sub.B, is controlled by a phase-locking loop including a phase comparator to which the reference frequency f.sub.B is fed along with a like frequency obtained from output frequency f.sub.A with the aid of another divider having a digitally variable integral step-down ratio g:1. A fractional value i, which may range from 0 to 100%, is set with the aid of a numerical interpolation selector to determine the number n<m of cycles of operating frequency f.sub.Q within a cycle (or half-cycle) of reference frequency f.sub.

Abstract: Two (or more) periodically reproducible input signals V.sub.yI, V.sub.yII, possibly including a constant reference signal, are visually displayed on an oscilloscope screen with the aid of a normally suppressed electron beam under the control of a horizontal-sweep generator and a vertical-sweep generator producing a sinusoidal x-deflection and y-deflection signals V.sub.xR and V.sub.yR, respectively. The x-deflection signal V.sub.xR is continuously compared with two (or more) ramp signals V.sub.xI and V.sub.xII, of different periodicities substantially lower than the frequencies of the deflection signals, respectively assigned to the input signals V.sub.yI, V.sub.yII to be displayed; upon the occurrence of a coincidence with one of these ramp signals, the horizontal sweep is halted or slowed down -- preferably to the slope of the coincident ramp signal -- for a display interval equaling one cycle of the y-deflection signal V.sub.