Abstract: A digital system is provided for synthesizing individual voices of musical instruments, which may then be combined into a musical composition. The system for a single voice is comprised of means for solving a system of simultaneous finite difference equations, where time is represented by real time in the computations. Musical sounds of the voice can then be produced by repetitiously solving the difference equations that model the instrument in real time, using an array of elemental means named "universal processing elements" (UPEs) interconnected by a matrix to each other and to external input and output terminals, and varying the sounds by varying the parameters. Each UPE is capable of computing Y=A+(B.times.M) from pipelined bit-serial inputs. The difference equations model a general linear filter, a second-order linear filter, a nonlinear polynomial function, and a random number (noise) generating function.

Abstract: A detection system having sending units for sending data signals representative of a condition, such as fire, smoke, intrusion, battery condition, or an emergency, to a central receiving unit. The sending units include a microcomputer which generates a pseudo-random number, waits for a number of cycle periods equal to the pseudo-random number, then activates a transmitter to send a data signal to the receiving unit. The randomized transmission prevents the synchronized clashing of transmitters.

Abstract: A frequency-stabilized oscillator is frequency modulated by band-limited random varying signals used to drive a suitable transducer randomly to and artificially perturb fluid jets in an electrostatic fluid jet applicator. Such random artificial pertubation is desirable (especially with longer cross-machine orifice plates) so as to obscure printing irregularities caused by standing wave or other phenomena. However, such random variations are best made with respect to a highly stabilized center frequency.

Abstract: This invention is a circuit for generating a framing pattern consisting of a pseudo random shift register sequence. This circuit utilizes an extremely long framing pattern without either a large amount of memory or the need to receive a large number of bits in order to recognize the framing pattern. The use of lengthy framing patterns minimizes the chance of false framing caused by patterns in bit positions other than the framing bit position.

Abstract: A pseudorandom noise generator (10) is disclosed which includes a maximum length sequence generator (13) for providing a digital signal having a pseudorandom sequence, modulating circuitry (17,20, 25, 27, 33) responsive to the digital signal for providing a constantly changing modulation signal which changes linearly. In one embodiment, the modulation circuitry provides a sequence of linear ramps which remain within predetermined limits, and a voltage controlled oscillator (29) responsive to the modulation signal for providing a pseudorandom noise output VCOUT. The modulating circuitry causes inversion of the slope of the ramps when they reach the predetermined limits.

Abstract: Method and apparatus for varying the output signal frequency of a controlled oscillator. The oscillator control signal is formed by filtering the output of a random number generator in such a way that the oscillatory output signal has a random frequency walk phase characteristic having predetermined, controlled characteristics.

Abstract: A digital noise generator for use in aeroengine noise testing can accurately and repeatably reproduce a standard noise spectrum so that differing noise analysis systems can be calibrated to a common standard. The noise generator comprises a pseudo-random binary sequence generator which is fed with a low clock frequency derived from a high frequency crystal oscillator. The generator produces a pseudo-random noise single bit signal which is fed to the most significant bit input of a digital to analogue converter, whose other inputs are fed with simulated tone data residing within an EPROM, the pseudo-random and tone noise thereby being digitally summed before conversion to an output analogue signal of desired spectral characteristics.

Abstract: A small battery operated nuclear spectrum simulator having a noise source nerates pulses with a Gaussian distribution of amplitudes. A switched dc bias circuit cooperating therewith generates several nominal amplitudes of such pulses and a spectral distribution of pulses that closely simulates the spectrum produced by a radiation source such as Americium 241.

Abstract: Method and apparatus for varying the output signal frequency of a controlled oscillator. The oscillator control signal is formed by filtering the output of a random number generator in such a way that the oscillatory output signal has a random frequency walk phase characteristic having predetermined, controlled characteristics.

Abstract: Randomly generated artificial perturbation signals are acoustically coupled to fluid jets to artificially stimulate droplet formation at a rate which varies. Such changes minimize the discernible effects of anomalies in droplet formation (e.g. along the cross-machine dimension of an extended orifice array) caused by standing acoustic waves or other phenomena. A relatively low frequency bandwidth-limited square wave with randomly occurring transitions has a controlled amplitude related to a desired magnitude of deviation in the rate of droplet stimulation. This first random signal is used, in the exemplary embodiment, to control the frequency of a frequency modulated oscillator having a relatively higher mean frequency related to the naturally expected rate of droplet formation. As a result, piezoelectric crystal drive furnished by the oscillator randomly varies between upper and lower frequency limits.

Abstract: A pseudorandom noise generator which operates in different modes is disclosed. The pseudorandom noise generator (10) includes circuitry (11,13) for providing a digital signal having a pseudorandom sequence at a selected clock rate; a modulation control circuit (15, 17, 20, 23) for selectively providing a modulation control signal that corresponds to either a non-filtered or filtered version of the digital signal, and for controlling the mode of operation of the noise generator; a modulation circuit (27, 29, 31, 33) responsive to the modulation control signal for providing a modulation signal; and a voltage controlled oscillator (VCO) (35) responsive to the modulation signal for providing a VCO output having a relatively constant output spectrum and high spectral containment for each mode of operation pursuant to control by the modulation control circuit and the modulation circuit.

Abstract: A random number generator (RNG) uses an edge-triggered D-type flip-flop with a high frequency square wave having an approximately 50 percent duty cycle connected to a data input terminal and a low frequency square wave connected to a clock input terminal, a five-state counter, five two-input AND gates, five exclusive-OR gates, and five shift registers. An essentially truly random number is generated at the RNG output terminals. Probability biases due to both variations in the 50 percent duty cycle of the data waveform and small amounts of cycle-to-cycle jitter of the clock waveform are effectively removed.

Abstract: A circuit for generating a noise signal for use in a jet engine noise simtor which utilizes two component pseudo-random noise (PSN) generators and a combination field effect transistor (FET) and resistor circuit to which the outputs of the PSN generators are connected such that the signal from one PSN generator is modulated by the signal from the other PSN generator.

Abstract: A portable low-output-level generator producing simultaneous audio, ultrasonic and RF noise for the test and demonstration of instruments designed to locate electrical interference, for demonstration of the broad frequency spectrum of electrical noise radiation, for antenna tests, to test the EMI susceptibility of electronic equipment, and to illustrate the effects of said noise on TV and radio receivers. This generator is enclosed in a housing and communicates audio and ultrasonic sounds to the observer via a vibrating diaphragm mounted on the face of the housing, with means provided to attenuate the audio sounds relative to the ultrasonic, and this generator radiates RF from a retractable antenna mounted on and extending outward from the housing.

Abstract: An apparatus and method is disclosed that provides a random data generator that is less susceptible to error sources resulting from negative feedback biasing. This invention utilizes a shift register and a multiplexer, controlled by the shift register, to provide the feedback to an amplifier. This improves the correlation between the present data output bit and the following bit.

Abstract: This invention is a circuit for detecting a framing pattern consisting of a pseudo random shift register sequence. This circuit utilizes an extremely long framing pattern without either a large amount of memory or the need to receive a large number of bits in order to recognize the framing pattern. The use of lengthy framing patterns minimizes the chance of false framing caused by patterns in bit positions other than the framing bit position. In addition, the incoming data stream may be connected directly to the shift register mechanism.

Abstract: Rhythm sound data which represents a rhythm sound such as a percussion sound, is synthesized with envelope data by a gate circuit which functions as a multiplier. The synthesized data is supplied to a D/A converter and converted to an analog signal. A percussion sound with a rhythm pattern corresponding to the analog signal is produced at a speaker.

Abstract: A random pulse generator which includes a voltage-to-frequency converter coupled to a voltage source providing a random voltage sequence, produces a train of logic pulses that can be randomized in a multi-mode manner on either a pulse rate or period basis with control over the percent variability. The durations of the on-off portions of the pulse train are separately adjustable.

Abstract: A Gaussian noise generator having a sample and hold circuit connected to the output thereof for providing random voltage samples, a voltage controlled oscillator controlled by the random voltage samples and providing a linear 10 sawtooth output having a frequency dependent upon the amplitude of the random voltage samples, and a second sample and hold circuit connected to the oscillator to provide random voltage output samples with substantially uniform distribution between predetermined limits.

Abstract: A randomized-clock circuit produces a random pulse train of predetermined sequence length and truncated exponential distribution of the gaps between pulses by multiplying a periodic clock signal with the output signal of a maximal length pseudorandom sequence generator which is clocked by the periodic clock signal. Control circuits monitor the maximal length pseudorandom pulse generator to start or stop random pulse sequences; random sequences are repeatable and a circuit to preset their starting point is provided. Cascading or connecting randomized-clock circuits in XOR, OR or AND gates is used to change the parameters of the exponential distribution function of the gaps. Pulse width and amplitude adjusting circuits allow interfacing of the randomized-clock circuit (a) with trigger inputs of medical and scientific pulse generators and (b) with electrodes connected to primates when the randomized-clock circuit is used as a nerve and/or muscle stimulator.

Abstract: A digital random error generator for generating burst errors comprises a first digital random error generator arrangement including a first pseudo random generator and a static random number generator for generating burst start signals at random times, a second digital random error generator arrangement including a second pseudo random generator and a second static random number generator for generating burst errors of random duration, and a flip-flop circuit receiving the outputs of the digital random error generator arrangements whereby the output of the second digital random error generator arrangement is enabled in dependence on the output of the first digital random error generator arrangement, so that the digital random error generator supplies a burst error of random duration starting at each above-mentioned random time.

Abstract: A digital processor (16) is disclosed for improving the statistical characteristics of nondeterministic random-like binary sequence. The basic elements of the digital processor are a feedback loop comprising a delay (17) and a signal combiner (18) and a subsampler (19). Maximum performance of the digital processor is achieved when a relatively prime relationship exists between number of cells in the delay (17) and ratio of the original signaling rate to the output signaling rate of the subsampler (19). Mathematical analysis is presented for showing that the digital processor improves both the equidistribution of the binary variable and autocorrelation statistic of output signal over the nondeterministic random-like binary signal. A further improvement in statistical properties is obtained by using two digital processors (116 and 121) in serial fashion.

Abstract: The timer generates a selected number of control pulses per hour, at unpredictable (pseudo-random) intervals, for use with a time lapse video tape recorder used for time studies. The hour is divided into equal intervals to provide the number of samples required per hour, and one trigger pulse is generated randomly timed within each interval. A noise generator drives a counter whose outputs are loaded every Nth clock pulse into an N-stage shift register. The contents of the shift register are shifted out serially at the clock frequency.

Abstract: Liquid jet printer apparatus and method includes the purposeful addition of random acoustic vibrations to the system so as to reduce adverse printing effects otherwise caused by standing acoustic waves along the length of an orifice array. As a result, a longer cross-machine dimension for the printer orifice array is made practical as may be required, for example, for some textile applications.

Abstract: An event selector includes a random number generator for randomly generating 2.sup.N N bit words, first and second memories each having 2.sup.N/2 storage locations with each storage location containing a predetermined stored word and each responsive to selected N/2 bit portions of each of the 2.sup.N N bit words to output the contents of the storage locations accessed by the selected N/2 bit portions, and an output terminal. Also provided in gating logic for gating only the outputted contents of all but X selected storage locations of the first memory to the output terminal and to gate only the outputted contents of the second memory to the output terminals when any of the contents of the X selected storage locations are outputted.

Abstract: A printer having greatly reduced radio frequency interference from the system clock signal therein is provided by angle modulating the system clock signal in accordance with a desired modulation signal. The modulation signal is chosen so as to spread and thereby reduce the energy level of the system clock signal at the carrier and at the harmonics without interfering with proper detection of the system clock signal by the electronic circuits within the printer requiring the clock signal for proper timing. In a first embodiment the angle modulation is provided by an FM modulator responsive to a modulating signal which is either sinusoidal or randomly varying in nature. In a second embodiment the angle modulation is provided by an arrangement which combines a modulated subcarrier with the basic clock frequency in a phase locked loop.

Abstract: In order to test coding rule infraction test units for AMI code which are employed for surveillance of digital transmission circuits, an arrangement is provided which generates quasi-random sequences in the AMI code without employing a spur line short-circuited at its end. Previously, no coding rule infractions could be mixed into the generated signals with such a spur line usually employed for generating signals in the AMI code. With the disclosed arrangement a generator for binary quasi-random sequences is provided to whose output one input of a differential amplifier arrangement is directly connected. Another input of the differential amplifier arrangement is connected via a series connection of an exclusive OR element and a time-delay element. Noise pulses which lead to coding rule infractions in the generated output signals can be mixed in via the other input of the exclusive OR element.

Abstract: A noise source is coupled through a first bandpass filter to a first mixer to which a first local oscillator signal is applied. The output of the first mixer is coupled through a second bandpass filter to a second mixer to which a second local oscillator signal is applied. At the output of the second mixer is obtained a noise signal having a bandwidth that can be varied by varying the frequency of the first local oscillator, and having a center frequency that can be varied by varying the frequency of the second local oscillator.

Abstract: A reliable, repeatable and stable VLF/LF atmospheric noise generator is cble of producing noise with known or given amplitude probability distributions and temporal characteristics such as pulse duration, pulse spacing, pulses per unit time and the discharge fine structure between pulses. A pseudo random noise carrier signal is multiplied in a plurality of digital-to-analog converters with the discharge envelopes created in a plurality of interconnected discharge envelope generators. The discharges are representative of cloud-to-ground discharges, intercloud discharges, the discharge rate, strokes per discharge and the discharge fine structure. All of the discharges are readily modifiable by suitably reprogramming operatively coupled memories and microprocessors in accordance with selected loading instructions.

Abstract: A Rayleigh fader for use with signals such as single-sideband and AM radio signals applies those signals to a 90-degree power divider. Each of the outputs of the power divider is taken to a separate double balanced mixer. Each separate double balanced mixer receives a mixing input from a noise source that includes a voltage-to-current converter. Mixed outputs of the two double balanced mixers are re-combined in a power combiner to produce a Rayleigh faded output.

Abstract: A test signal generator for pseudo-simulated non-intelligible speech. The generator comprises first and second ROM's controlled by first and second address counters driven by a single clock. The first ROM generates digital samples which when decoded produce a random signal having a gaussian amplitude distribution. The second ROM also generates digital samples which when decoded produce a modulating signal having a power spectrum substantially equal to that of the modulation envelope of speech and a wave shape that results in a gamma amplitude distribution of a gaussian amplitude distributed signal. Each cycle of the modulating signal has an identical wave shape but a randomly varying wave period.

Abstract: Compression and synthesis techniques and related apparatus for time domain signals, particularly signals whose information content resides in the power spectrum such as speech and more particularly signals whose amplitude is aperiodic, such as unvoiced speech sounds. Compression techniques include eliminating serially redundant segments of information. Synthesis, particularly of unvoiced sounds which are sensitive to injected artificial periodicity, involves repeating sequentially portions of the same segmentrepresentative of the source signal, including commencing and terminating at different points each repetition, varying the length of the portion and reproducing the portion forwards and backwards in time. The invention finds application in speech compression and compact speech synthesis devices.

Abstract: Compression and synthesis techniques and related apparatus for time domain signals, particularly signals whose information content resides in the power spectrum such as speech. Compression techniques include adjusting the phase of harmonic components of a signal unit to obtain an equivalent power spectrum signal of a minimum number of discrete levels. The invention finds application in speech compression and compact speech synthesis devices.

Abstract: A simulated-noise signal is injected in the power line of equipment under test without loss of AC power by the use of a series resonance circuit having a resonance frequency equal to the frequency of the AC power supply. The series resonance circuit is connected in the power line in parallel with the equipment, and a capacitor is connected to the power line in parallel with the series resonance circuit and the equipment. A switching element is used to short-circuit the resonance circuit when noise simulation is not carried out. For the simulation of lightening strikes the circuit further comprises a simulated-noise signal generator including a capacitor charged by a DC power supply, a first switching element to discharge the charge of the capacitor to the equipment, and a second switching element for establishing a by-pass of the discharging current. By closing the second switching element after the first switching element is closed, a square-wave signal is fed to the equipment.

Abstract: A pseudo random number generator for generating a succession of numbers manifesting solely three values at random from two-bits.

Abstract: A digital noise generator, wherein pseudo-random rapidly changing analog input voltages to a voltage controlled oscillator are used to generate corresponding rapidly changing discrete frequency outputs, is disclosed. Means are provided to delay the oscillator output by an amount at least equal to the rise time between each frequency change. The delayed and non-delayed oscillator outputs are electrically coupled through a switch that operates at times and at a rate to eliminate the rise time between frequency changes and thus improve the frequency spectrum.

Abstract: A precision digital random data generator comprising a matched pair of D-type flip-flops, a differential amplifier for comparing integrated outputs of the flip-flops, provisions for a noisy analog input of the general type (n)t feeding one input of the comparator with the output of the comparator feeding a D input of one of the D type flip-flops which generates an output which statistically correlates with the analog input and is also fed to the other input of the comparator.

Abstract: A piezoelectric audible sound generator having a feedback type piezoelectric transducer, an amplifier, and a phase compensator for adjusting the phase shift due to the combination of a bias resistance of the amplifier and equivalent capacitance of the piezoelectric transducer.

Abstract: A test instrument for generating controlled bursts of electrical noise for use in testing the response of electronic equipment to such noise. A high voltage induction coil has its primary winding connected in circuit with a semiconductor switching means across a source of DC potential whereby when the current flow through the primary winding is interrupted, a relatively high voltage is developed across spark electrodes connected in the secondary winding of the coil and a spark discharge results. The spark discharge is, of course, rich in high frequency noise components which radiate therefrom to the system under test. The test instrument includes controls for causing the spark discharge to be generated either when triggered by a signal from the system under test, or by the manual operation of a push button switch, or at rates which may be varied by the operator.

Abstract: An improved pseudo-atmospheric noise generator includes the capability for roducing noise in the VLF/LF spectrum with known amplitude probability distributions while controlling the temporal characteristics of the simulated impulses. The outputs from a number of pseudo-random bit generators are selected by a microprocessor in accordance with expected or anticipated atmospheric disturbances from a number of geographical regions. The microprocessor selected outputs are fed to a digital-to-analog converter which feeds the converted signals to a summer. An independent Gaussian noise source is coupled to the summer and the outputs from the Gaussian noise source and the digital-to-analog converter are combined to create a composite pseudo-atmospheric noise signal. The improvement also includes capability for self-testing and set up.

Abstract: A random number generator that provides bits at its output that are neither biased nor periodic. The generator includes a noise generator and sampling register that provide serial, randomly varying bits. A circuit within the generator for reducing auto-correlation or periodicity discards certain ones of the randomly varying bits, and includes a first shift register for receiving and storing the randomly varying bits and a second register for receiving in parallel and storing only a portion of the randomly varying bits from the first register. In order to eliminate bias, EXCLUSIVE OR gates are connected between the first and second registers in order to logically combine the randomly varying bits received by the second register with previous bits stored in the second register.

Abstract: A pseudorandom binary sequence generator employing a conditional feedback path between several individual outputs and the input of a clocked shift register. Enhanced reistance to a latchup condition is brought about by way of a delay of one of the outputs, relative to the other outputs, as coupled to the feedback path.

Abstract: A waveform capable of jamming some or all of the channels of a multiple channel receiver is developed by a multi-tone jammer that uses a digital counter and a digital/analog converter to generate a ramp voltage for a voltage controlled oscillator (VCO). The output of the VCO is modulated by a pin diode attenuator. The attenuator is controlled by a pattern generator synchronized with the digital counter to blank the retrace and any portion of the sweep to provide a partial band tone jamming spectrum. The digital counter is driven by a MHz reference signal generator and the sweep repetition rate is greater than the circuit bandwidth.

Abstract: A signal generator for testing the dynamic headroom characteristic of audio amplifiers. The signal generator provides a signal comprising 20 cycles of a 1000 Hz sinewave followed by 480 cycles of a sinewave at the same frequency and having a level of -20 dB relative to the 20 cycle burst. The dynamic headroom test generator signal processing provides a test signal amplitude HI/LO ratio of 10 to 1, and a HI/LO timing ratio not subject to change from 20/500 cycles, whatever audio frequency is utilized.

Abstract: A logic system for implementation of a feed-forward non-linear generator for producing a plurality of programmable complex sequences from an input bit stream.

Abstract: An electric circuit, in particular for devices and systems operating on an SSMA basis, for the production of a number of different codes according to a linear law of formation and having practically negligible values of cross correlation coefficients and autocorrelation coefficients during a shifting time and characterized by the provision of two basic code generators respectively consisting of a sequential network, at least one-half adder and at least one delay network, the half adder representing the output circuit, wherein one of the two codes is respectively given at both outputs of the half adder and the delay network is arranged in the connection path which extends between one of the two basic code generators and the half adder.

Abstract: The frequency of a reference oscillator is controlled by a reference voltage which is altered at the beginning of an output cycle to equal the instantaneous value of the averaged outputs of a first oscillator and a second oscillator. In a preferred embodiment, the outputs from the reference oscillator and the second oscillator are summed, and this voltage is used to control the power output to a load.

Abstract: A noise generator in which a random pulse output is produced by a random pulse generator in synchronism with a predetermined clock and is stored in a latch circuit by a clock obtained by frequency dividing the predetermined clock to produce random pulses of a harmonic composition different from the abovesaid random pulse output, thus providing noises of two or more desired harmonic compositions from the random pulse generator.

Abstract: An apparatus for testing digital logic circuits without a computer and associated software employs a psuedorandom stream of input data to produce an unstructured output data stream which is analyzed by an efficient data collector and analyzer. Test signal generation is implemented by a pseudorandom number generator and a pseudorandom clock/reset generator while the resulting test data at the output terminals of the device under test is analyzed by a cycle redundancy code checker. Fault localization is realized, with selectable localization and manual probe modes and circuitry is provided for an efficient self-test mode.

Abstract: Apparatus for generating noise is described incorporating means for generating a noise frequency spectrum, a plurality of voltage controlled oscillators and means for coupling the voltage controlled oscillators to an output.The invention overcomes the problem of a single voltage controlled oscillator which could not slue and settle at an appropriate frequency prior to being coupled to an output which resulted in undesired frequencies being generated during this slueing and settling time.