Showing papers on "Signal published in 1984"

On the ability to inhibit simple and choice reaction time responses: a model and a method

Abstract: This article reports four experiments on the ability to inhibit responses in simple and choice reaction time (RT) tasks. Subjects responding to visually presented letters were occasionally presented with a stop signal (a tone) that told them not to respond on that trial. The major dependent variables were (a) the probability of inhibiting a response when the signal occurred, (b) mean and standard deviation (SD) of RT on no-signal trials, (c) mean RT on trials on which the signal occurred but subjects failed to inhibit, and (d) estimated RT to the stop signal. A model was proposed to estimated RT to the stop signal and to account for the relations among the variables. Its main assumption is that the RT process and the stopping process race, and response inhibition depends on which process finishes first. The model allows us to account for differences in response inhibition between tasks in terms of transformations of stop-signal delay that represent the relative finishing times of the RT process and the stopping process. The transformations specified by the model were successful in group data and in data from individual subjects, regardless of how delays were selected. The experiments also compared different methods of selecting stop-signal delays to equate the probability of inhibition in the two tasks.

Method and apparatus for marking the information content of an information carrying signal

Abstract: An information signal (INF) which is transmitted in coded form (CINF) from a signal source (RC) to a signal receiver (4, 5) is decoded at the receiver and at the same time marked (MINF) by the introduction of an identification information (ID) which is characteristic of the receiver or its possessor. The signal from a video disc (RC) carrying a coded programme is decoded and marked before it is supplied to a television set (6). Via said identification information of so-called pirate copy is directly traceable to its originator. Thereby a protection against such copying is obtained. A device for the playback of a video disc of this type comprises a decoding and modification unit to which the necessary decoding information and identification information may be supplied from a personal data carrier (ID).

Out-of-range personnel monitor and alarm

Abstract: An out-of-range monitor and alarm system that may be used by a convalescent home or the like to alert an attendant in the home that a supervised person has walked beyond a predetermined prescribed distance. The system includes a base unit that transmits a signal at a frequency F1 to a receiver in a mobile unit carried by the supervised person. The receiver includes a threshold circuit that is adjustable to correspond to the prescribed distance and produces a threshold output signal whenever the F1 signal detected by the receiver drops below the threshold level. In response to the threshold output signal, a transmitter in the mobile unit produces an F2 output signal to a receiver in the base unit, which in turn sounds an alarm indicating that the mobile unit has lost adequate F1 signal strength, as determined by the threshold adjustment, by exceeding the range prescribed for the supervised person.

Comparing Spectra of a Series of Point Events Particularly for Heart Rate Variability Data

Abstract: Different methods for spectral analysis of the heart rate signal?considered as series of point events?are used in studies on heart rate variability. This paper compares these methods, focusing on the two principal ones: the interval spectrum, i.e., the spectrum of the interval series, and the spectrum of counts, which is related to the representation of the event series as a series of spikes (delta functions). Both autospectra are estimated for experimental heart rate data and are shown to produce similar results. This similarity is proven analytically, and it is shown that for small variations in interval length, the ratio of these spectra is PI(f)/PC(f) = [sin(?f?)/(?f?)]2, with PI and PC the interval spectrum and the spectrum of counts, respectively, f the frequency, and ?the mean interval length. It is concluded that both autospectra are equivalent for the considered heart rate data, but that, when relating the heart rate signal to other signals (e.g., respiration, blood pressure) by means of cross spectra, the technique to be used depends on the characteristics of the second signal.

Modem for pseudo noise communication on A.C. lines

Abstract: A modem which may operate as a transmitter or receiver, is provided for use on a line carrying an A.C. signal. The modem comprises a pseudorandom code generator which produces a pseudorandom code signal of a frequency an integral multiple of the A.C. signal frequency. Synchronization means synchronizes the code signal with the A.C. signal. Preferably a coherent system is provided in which a data signal involved has a bit rate an integral multiple of the A.C. signal frequency and in which a carrier generator is additionally provided to produce a carrier signal of a frequency an integral multiple of the A.C. signal frequency. In such case, the synchronization means also synchronizes the data bit and carrier signals with the A.C. signal.

Electrosurgical generator with high-frequency pulse width modulated feedback power control

Abstract: A pulse width modulation technique regulates the output power of each cycle of a radio frequency surgical signal of an electrosurgical generator. The delivered power of the surgical signal is determined by multiplying the sensed current and the sensed voltage of the surgical signal. An error signal is established by the difference of the actual delivered power with respect to a selected desired output power. The error signal is operatively utilized to modulate the pulse width of each driving pulse which creates the cycles of the surgical signal. Limits on the sensed voltage and sensed current signals are established to limit the output characteristics of the surgical signal. A minimum current limit signal is utilized to limit the maximum output voltage into relatively high impedances. A minimum voltage limit signal is utilized to limit the maximum output current into relatively low impedances. Very rapid response times and very effective power regulation even into relatively high impedance tissues are possible with the pulse width modulation technique. The risks and problems associated with open circuit flashing, alternate path burns and closed circuit shorting are substantially reduced or eliminated.

Spread spectrum radio transmission system

Abstract: A communications system wherein an intelligence signal modulates the spacing of relatively narrow pulses of a fixed rate pulse train, and these pulses key on a transmitter which employs a pair of series connected avalanche mode operated transistors. These are repetitively powered via a charged coaxial delay line, and the output, appearing across a resistive load, is fed directly, or through a shaping filter, to a discone transmitting antenna. At a receiving location, the received signal is amplified by a wide band amplifier and fed through a reverse contoured filter (of the transmitting filter, if one is employed). The signal is detected via synchronous detection which locks onto the received pulse train, after which the modulation evidence by the pulse train is recovered by a low pass filter.

Signal processor for laser Doppler tissue flowmeters.

Abstract: Laser Doppler flowmeter for the assessment of tissue blood flow are generally equipped with a signal processor which generates the first moment of the unnormalised power spectral density as a continuous output signal. This signal is related to blood flow for low and moderate flow rates. At higher flow rates the interpretation of the output signal becomes ambiguous as a consequence of the multiple scattering in moving blood cells and the homodyne mixing of waves on the detector surface. The paper describes a new signal processor which takes these effects into account and establishes a linear relationship between the flowmeter output signal and blood flow for all flow rates. The performance of the signal processor was evaluated by an experimental fluid model which optically resembled the blood flow through the microvasculature. The transiently high blood flow in the initial phase of reactive hyperaemia, recorded from palmar skin, gave peak values which were almost double those recorded with the original signal processor of the flowmeter. In conjunction with these high peak values a high concentration of moving blood cells was recorded, indicating that the initially high flow rate is produced by an increased number of moving blood cells due to vasodulation rather than by a change in average velocity.

Phase and amplitude recovery from bispectra

Abstract: The bispectrum is the Fourier transform of the triple correlation, sometimes also referred to as triple product integral. We are concerned here with the bispectrum of the autotriple correlation. Bispectrum analysis can be used to solve phase problems in signal processing, since the knowledge of the bispectrum of a signal usually allows one to reconstruct both amplitude and phase of the Fourier transform signal. We present mathematical proof based on the theory of analytic functions and discuss the restrictions involved. A recursive algorithm is outlined for the reconstruction from sampled data. In addition, possibilities for noise reduction by averaging redundant information will be described. Examples are included for 1-D signals.

Key signal encryption and distribution system for controlling scrambling and selective, remote descrambling of television signals

Abstract: A system and method for scrambling and selectively descrambling television signals that are transmitted to subscribers' descramblers in a subscription television system. A working key signal is generated by processing an "initialization vector" signal in accordance with the DES algorithm upon the algorithm being keyed by either a common category key signal or a signal having a predetermined relationship to the common category key signal. A unique encryption keystream is generated by processing the initialization vector signal in accordance with the DES algorithm upon the algorithm being keyed by the working key signal. A television signal is scrambled in accordance with the unique encryption keystream to provide a scrambled television signal. A plurality of unique encrypted category key signals individually addressed to different selected subscribers' descramblers are generated by processing the initial common category key signal in accordance with the DES algorithm upon the algorithm being keyed by a plurality of different "unit key" signal unique to different selected descramblers. The scrambled television signal. the initialization vector signal, and the plurality of encrypted category key signals are broadcast to the descramblers. A corresponding tier of DES algorithms are employed at the descramblerto reproduce the encryption keystream; and the TV signal is descrambled in accordance therewith. Each descrambler has its unique unit key signal stored in a secure memory for use in reproducing the common category key signal when the descrambler is addressed by its unique encrypted category key signal.

Apparatus and method for a universal electronic locking system

Abstract: An apparatus and method for providing a universal electronic locking system (UELS) which controls an actuating device for a lock (86) The system is composed of two elements, a signal-transmitting unit (10) and a signal-receiving unit (40) The integrated circuit chip of the watch (12) is expanded to include a programmable memory unit such that various codes may be entered in the watch and the codes may be changed at any interval desired by the operator The signal-receiving unit comprises a photodetector (48) for receiving an optical signal (34) from the signal-transmitting unit (10) and contains a programmable memory unit (54) which is responsive to each and all codes contained in the signal-transmitting unit Upon changing the code signal in the signal-transmitting unit (10), the memory unit (54) of the signal-receiving unit (40) may be reprogrammed so as to be responsive to the newly encoded signal and allow the latching mechanism (60) of the lock system to be operated The system may be used alone or in combination with conventional key (122) operated locking mechanisms The UELS is contemplated for applications in the home, business, industry, recreation, defense and wherever locks and codes are used

Digital I2 T pickup, time bands and timing control circuits for static trip circuit breakers

Abstract: Digital implementation of the overcurrent determination and time delay before tripping in a static circuit breaker trip unit allows the trip unit circuit to be manufactured in a single chip configuration. The signal after A/D conversion is compared within a magnitude comparator to determine pickup. A pulse stream proportional to the square of the overcurrent signal is developed by multiplying the outputs of two magnitude comparators which compare the A/D level with a continuous binary count. The time delay determination is obtained by means of 3 cascade connected divide by two counters with their outputs connected to a data selector, or by a rate-limiter circuit which uses a fixed frequency to gate a pulse stream proportional to the overcurrent level squared.

Immunoassay using optical interference detection

Abstract: Apparatus and method for providing an optical detection of a binding reaction between a ligand and an antiligand, including, a pattern formed by a spatial array of microscopic dimensions of antiligand material, ligand material interacting with the antiligand material to produce a binding reaction between the ligand and the antiligand in the pattern, a source of optical radiation including energy at at least one wavelength directed to the pattern at a particular incidence angle to produce scattering of the energy from the pattern in accordance with the binding reaction and with a strong scattering intensity at one or more Bragg scattering angles, and at least one optical detector located relative to the pattern and aligned with a Bragg scattering angle to detect the strong scattering intensity at the Bragg scattering angle to produce a signal representative of the binding reaction.

Investigation of basic imaging properties in digital radiography. I. Modulation transfer function

Abstract: The effect of various digital parameters, such as the sampling aperture, sampling distance, and display aperture, on the modulation transfer function(MTF) of digital radiographicimagingsystems was investigated by means of theoretical simulation studies. The MTFs were also determined experimentally to confirm the relationship used in the simulation studies. The results indicate that the overall MTF of a digital system cannot specify the resolution properties in the same way as can the MTFs of analog systems. The MTF of a digital system may include a ‘‘false’’ response due to aliasing, which could lead to an incorrect interpretation of the resolution properties. The magnitude of aliasing that will occur in a digitized signal depends on the sampling parameters chosen and on the frequency content of the radiologic object being imaged. Thus, the type of object to be detected as well as various digital parameters must be considered in the design and evaluation of digital imagingsystems.

Brightness control system for crt video display

Abstract: A video brightness control system for high performance CRT displays including a buffer amplifier for receiving high speed video information and applying it to a gain control variable resistor serving as a contrast control. An ambient light sensor drives a nonlinear amplifier to provide an ambient light signal which is in proportion to the logarithm of the ambient light level over a wide range. A manual brightness control potentiometer is adjustable to provide a constant brightness signal. The video information signal, the ambient light signal, and the manual brightness control signal are added together by a summing device, with the resultant signal approximating a logarithmic characteristic. The output of the summing device is applied to a gamma correction amplifier which drives a video driver amplifier, the video amplifier, in turn, drives the CRT. The gamma correction amplifier and video driver in combination with the video transfer function of the CRT approximates an exponential transfer function, thereby creating CRT screen brightness which is an antilogarithmic function of the total video signal appearing at the gamma correction amplifier input. This results in automatic brightness control as a function of ambient light level, minimum interaction between brightness and contrast controls, and a gamma characteristic which provides a reasonable approximation to the variation of brightness difference threshold of the eye.

An Inexpensive Eye Movement Monitor Using the Scleral Search Coil Technique

Abstract: For the economical recording of eye movements using the scleral search-coil method, we developed a circuit using common components and costing only $300. The Helmholtz field coils are 51 cm in diameter and are separated by 51 cm. The horizontal and vertical field coils are driven at 50 and 75 kHz, respectively, by phase-locked square waves; no tuning is required. After amplification, the eye-coil signal is phase detected at 50 and at 75 kHz to produce the horizontal and vertical eye-position signals, respectively. For a 2 cm diameter eye coil of one turn, the noise is 1.0 min of angle rms.

Method and device for detecting a specific acoustic spectral feature

Abstract: A method and device for detecting a narrow acoustic spectral feature in a sample as described. The method uses an electrical frequency modulated (FM) signal that is obtained from a voltage controlled oscillator. The Fourier spectrum of this wave is a main frequency fc with two small sidebands at frequencies fc ±fs. This whole triplet is slowly swept in frequency by a slow sawtooth generator. The electrical signal is fed into a flat acoustic transducer; the acoustic wave is then transmitted through an acoustically active medium, i.e. the sample, and detected by another flat acoustic transducer which produces an FM signal with a superposed amplitude modulated (AM) signal if one of the sidebands overlaps an acoustic feature. This electrical signal is then demodulated to give a pure AM signal which can be phase sensitive detected by using a lock-in amplifier. By suitable adjustment of the phase setting of the lock-in amplifier both the "in-phase" and "out-of-phase" signals of the detected acoustic signal can be detected.

Significance of group delay functions in signal reconstruction from spectral magnitude or phase

Abstract: In this paper we discuss the problem of signal reconstruction from spectral magnitude or phase using group delay functions. We define two separate group delay functions for a signal, one is derived from the magnitude and the other from the phase of the Fourier transform of the signal. The group delay functions offer insight into the problem of signal reconstruction and suggest methods for reconstructing signals from partial information such as spectral magnitude or phase. We examine the problem of signal reconstruction from spectral magnitude or phase on the basis of these two group delay functions and derive the conditions for signal reconstruction. Based on existing iterative and noniterative algorithms for signal reconstruction, we propose new algorithms for some special classes of signals. The algorithms are illustrated with several examples. Our study shows that the relative importance of spectral magnitude and phase depends on the nature of signals. Speech signals are used to illustrate the importance of spectral magnitude and picture signals are used to illustrate the importance of phase in signal reconstruction problems. Using the group delay functions, we explain the convergence behavior of the existing iterative algorithms for signal reconstruction.

Acquisition circuit for cardiac pacer

Abstract: An acquisition circuit for a cardiac pacer includes an oscillator for producing an externally generated magnetic signal at a first predetermined frequency. An implantable cardiac pacer has a tuned inductor coil to be responsive to the magnetic signal for developing an induced signal with a phase-shift. Light-emitting devices are responsive to the magnetic signal and the induced signal are provided for transmitting optical signals which change gradually from flashing to a steady on condition when the telemetry head is moved closer to and adequately positioned over the cardiac pacer to indicate that positive acquisition has been obtained.

Simultaneous transmission of speech and data over an analog channel

Abstract: A technique for transmitting an entire analog speech signal (S(t)) and a modulated data signal (D(t)) over a transmission channel (20) such as a common analog telephone speech channel. The present technique multiplexes the entire modulated data signal within the normal analog speech signal frequency band where the speech is present and its signal power density characteristic is at a low level. Separation of the speech and data signals at the receiver (30) is effected by recovering the modulation carrier frequency (fc) and demodulating (33) the receiver signal (X(t)) to recover the data signal. The data signal is then remodulated (34) with the recovered carrier and is convolved with an arbitrary channel impulse response in an adaptive filter (35) whose output signal is subtracted (37) from the received composite data and speech signal (X(t)) to generate the recovered speech signal (S(t)). To improve the recovered speech signal, a least mean square algorithm (36) is used to update the arbitrary channel impulse response output signal of the adaptive filter (35).

System Optimization for Improved Accuracy in Transcutaneous Signal and Power Transmission

Abstract: A stable transcutaneous transmission of power and signal via two coupled coils with minimized dependence on the relative spacing of external and implanted coil is possible by employing "critical coupling" between implanted and external circuits. Optimizing coil geometries and preventing the RF output amplifier from saturating is necessary to approximately maintain critical coupling despite placement tolerances within a reasonable range. Based on these considerations a transcutaneous signal transmission system for an auditory prosthesis has been designed. This transmission system can also be used for several other stimulation purposes needing accurate control of stimulation parameters.

Real-time hierarchal pyramid signal processing apparatus

Abstract: Pipe-line architecture is employed for analyzing in delayed real time the frequency spectrum of an information component (having one or more dimensions) of a given temporal signal having a highest frequency of interest of no greater than f 0 , and/or for synthesizing in delayed real time such a temporal signal from the analyzed frequency spectrum thereof. Such pipe-line architecture is particularly suitable for image-processing the two-dimensional spatial frequencies of television images defined by a temporal video signal.

Recording apparatus producing multiple copies simultaneously

Abstract: The present invention provides a recording apparatus including a plurality of printers each for reproducing an image on a recording sheet upon receiving the same signal, and a single sheet delivering device for delivering recording sheets to the printers. The present invention also provides a recording apparatus including a plurality of printers each for reproducing an image on a recording sheet upon receiving the same signal, and a sheet discharge device for feeding the recording sheets from the printers to a collector or sorter.

Pulse-to-Pulse Coherent Doppler Sonar Signal Processing Techniques

Abstract: In this paper we present and discuss techniques for the computation of the mean and spectral variance of a pulse-to-pulse coherent sonar signal, leading to the measurement of mean water velocity and turbulence. The use of an autocovariance algorithm associated with a dual-pulse repetition rate (PRF) method is recommended. The dual-PRF method allows removal of velocity ambiguities due to signal sampling and also offers a convenient means for the estimation and removal of the receiver noise which otherwise would strongly bias the spectral variance measurements. The performances of the method are illustrated by presentation and discussion of data acquired in a tidal flow.

Patient controlled medication infusion system

Abstract: A medication infusion system which includes an infusion line for introducing medication to a peripheral vein of a patient. The infusion system includes a pump for delivering the medication and a pressure transducer within the infusion line for converting sensed fluid pressure waves to electrical signals. An amplifier is provided within the system for increasing the strength of the electrical signal. A gain control amplifier is electrically connected within the system for maintaining the electrical signal at a predetermined amplitude regardless of input variations. A tracking filter is provided within the system to provide an electrical signal representative of the patient's respiration rate over a preselected full clinical respiration rate range. A microprocessor is provided within the system for deriving from the electrical signal a control signal for controlling the operation of the pump. The microprocessor includes the ability to determine the presence or absence of the electrical signal representative of the patient's respiration rate, a comparator for comparing the rate signal with a preselected respiration rate and a storage capability for storing the rates and preselected rate values. The system further includes a motor control for providing a signal to the pump for actuating the pump in preselected increments when directed by the microprocessor.

Ultrasonic apparatus for positioning a robot hand

Abstract: A robot positioning apparatus for use with robot devices having a movable portion, wherein the movable portion may be spatially oriented to, and controllably spaced from, a reference surface. Initial locating of the reference surface is accomplished by an approximate positioning subsystem using multiple, angularly oriented units which send and receive acoustic orientation positioning signals in search of the reference surface. Once a return signal is received, switching logic identifies the necessary reorienting of the movable portion to achieve approximately the proper facing relationship of the movable portion to the surface. For precise positioning and ranging after the facing relation is established, a precision positioning subsystem emits an acoustic signal toward the surface, and a response signal is received back from the surface by at least two, and preferably three, receivers mounted upon the movable portion of the robot device. A comparator compares the times of flight of the signals received by the receivers on a pair-wise basis, thereby determining the relative distance of the pair of receivers from the surface, which in turn is a direct indication of the spatial orientation of the compared receivers in relation to the reference surface. The signal time of flight from the surface to the receivers is measured as an indicator of the distance of the receivers from the surface. The movable portion of the robot device is adjusted to maintain some predetermined distance and spatial orientation for the signal receivers mounted on the movable portion, thereby orienting the movable portion with respect to the surface in three dimensions.

Microwave multiport multilayered integrated circuit chip carrier

Abstract: A multilayered integrated circuit chip carrier has a top layer, a signal line layer, a ground layer, a power conductor layer, and a bottom layer with a separating layer between adjacent layers. Each layer has coplanar conductive and dielectric portions, the separating layers being primarily dielectric. The top layer supports an integrated circuit chip and signal launcher pads on the bottom layer couple signal and power lines of a printed circuit board to spaced points about the bottom layer periphery and substantially constant signal line impedance is achieved. The signal line layer is separated from the power conductor layer by a ground plane layer. Conductive via through pads are placed in the separating layers to form a plurality of separate conductive paths from each of the bottom and top layers to each of the signal line and power conductor layers. Via through pads are also placed in the separating layers to break up cavities and thus increase cavity resonance above signal frequencies and are placed in the signal line layer to provide signal line isolation. Thermal columns of via pads in the separating layers and conductive portions in the other layers under the chip provide chip cooling. Large grounded conductive areas in the top and bottom layers reduce unwanted signal coupling to the external environment. A capacitive coupling on the top layer between a power conductor and ground provides power line isolation.

Segmentation of coarticulated speech in perception.

Abstract: The research investigates how listeners segment the acoustic speech signal into phonetic segments and explores implications that the segmentation strategy may have for their perception of the (apparently) context-sensitive allophones of a phoneme. Two manners of segmentation are contrasted. In one, listeners segment the signal into temporally discrete, context-sensitive segments. In the other, which may be consistent with the talker’s production of the segments, they partition the signal into separate, but overlapping, segments freed of their contextual influences. Two complementary predictions of the second hypothesis are tested. First, listeners will use anticipatory coarticulatory information for a segment as information for the forthcoming segment. Second, subjects will not hear anticipatory coarticulatory information as part of the phonetic segment with which it co-occurs in time. The first hypothesis is supported by findings on a choice reaction time procedure; the second is supported by findings on a 4IAX discrimination test. Implications of the findings for theories of speech production, perception, and of the relation between the two are considered.