A circuit for linearizing the oscillator sweep output frequency signal of a oltage controlled oscillator is disclosed. The voltage controlled oscillator is driven by the output of an op amp, which amplifies and filters the output of a D/A converter. The D/A converter responds to preselected 8-bit words, stored in an EPROM, so as to produce a desired output frequency at each memory address. The addresses, in turn, are provided by a combination of gates, counters, input signals and a clock.
The damaging effects caused by an abrupt rise of the supply voltage on particularly sensitive circuits when power is returned to the distribution network after a blackout, are prevented by providing the power supply with means for controlling a gradual rise of the output voltage thereof in accordance with a pre-established ramp when the power supply is switched-on. These means utilize a microprocessor driving at least one low-to-high type level shifter having a load formed by a network of resistors with scaled values, for generating an output analog voltage signal corresponding to a digital value presented by the microprocessor at the logic gate driving the level shifter circuit. The analog voltage signal, properly buffered, is applied to a control terminal of the power supply.
A tone-pip signal generator for use in systems employed in the identification and diagnosis of hearing defects, the generator including a counter for counting cycles of a clock signal which occur following the time marked by a reset signal, a gate circuit for coupling the clock signal to the counter until a predetermined count is accumulated, a memory addressed by the counter, the memory for retrieving in succession stored numbers representing respective time samples of the tone-pip signal and a digital-to-analog converter driven by the memory. Additionally, the generator includes an exclusive-OR-gate array for selectively inverting the tone-pip signal.
In a clock generator circuit, a zero hold circuit produces from a fixed clock signal a zero hold clock signal which is in phase with an external sync signal. A phase comparator circuit produces phase difference data indicating the phase difference between the external sync signal and an internal sync signal. A counter cleared by the external sync signal counts pulses of the zero hold clock signal to obtain count data. A memory receiving the phase difference data and the count data as its address input produces the internal sync signal when the count data is smaller than the number of pulses in one cycle of the external sync signal having no time-base variations, and a phase control signal determined by the phase difference data and the count data. A phase shifter shifts the phase of the zero hold clock according to the phase control signal to obtain a modified clock signal synchronized with the external sync signal.
Existing auditory warning systems are in general too loud and it is often difficult to distinguish between a number of different warnings. Further under different conditions warnings may change character due to masking by varying noise. A warning system is disclosed which is based on a microprocessor and waveforms for each warning sound stored in a ROM. The waveforms are read out to DACs and used to drive a loudspeaker by way of programmable attenuators. Each waveform is devised to have at least four quasi-harmonically related frequency components at a power level in the range 15 to 30 dB above threshold. In this way the sounds are distinctive and do not change character with varying noise levels below threshold.
Disclosed is a real time interference signal rejection circuit which utils a conventional chirp-Z analyzer to generate a critical number and stop a counter circuit. The critical number is then read by a microprocessor which calculates new tap values from a set of predetermined tap values to reprogram a programmable filter.
