Showing papers on "Digital signal published in 1979"

Method and apparatus for speech synthesizing

Abstract: A speech synthesizer including a device for storing compressed digital signals corresponding to original information speech or audio waveform time domain signals, the digital signals including information signal portions and instruction signal portions identifying particular compression techniques applied to associated information signal portions; an output terminal for manifesting analog electrical synthesized signals corresponding to the original signals; a digital-to-analog converter having an output coupled to the output terminal and an input; and an intermediate signal processing circuit having an input coupled to the storage device and an output coupled to the digital-to-analog converter for expanding the information signal portions in accordance with the instruction signal portions to produce digital synthesized signals to be converted to analog synthesized signals by the digital-to-analog converter.

A high-speed 7 bit A/D converter

Abstract: A 7 bit two-step parallel A/D converter has been designed using a new quantizer-subtractor circuit. The small delay in the new circuit allows digital signal sampling by latching comparators. A sample and hold unit is not needed which results in a fully integrable A/D function. Analog input signals up to 5 MHz can be digitally sampled with sampling frequencies up to 50 MHz. A double layer metallization process is used to reduce the die size to 2.4/spl times/2.5 mm.

Device to control machines by voice

Abstract: A device to control machines by voice is disclosed which responds to a plurality of predetermined musical tones in a sequence to generate a digital control output signal. Audio conversion means convert the sequence of tones into a corresponding sequence of digital number signals which are temporarily stored in a memory. Then a sequence of ratio signals are generated by dividing each of the digital number signals by one of the digital number signals. The resulting sequence of ratio signals is then converted into a corresponding sequence of digital numbers which comprises the digital control output signal. A microprocessor and associated storage processes the digital data and controls the conversion of the musical tones into corresponding digital numbers.

Data storage and retrieval structure for a message storage system

Abstract: A message storage system (104) cooperates with a plurality of telephone switching offices (102, 122) to provide a variety of voice storage services to subscribing customers served by the switching offices. Control signals and voice messages are delivered to the message storage system in analog form and converted to digital signals. A processor circuit (111) interprets the control signals and sends work lists to a plurality of microprocessor controlled message controllers (113a through 113n) which in turn each control a plurality of disc transports (114a through 114n), a time multiplex switch (115), and a larger plurality of buffer circuits (116) wherein the messages in digital signal form are speed buffered for storage in the disc transports. The message controllers control the flow of digital data words between the buffer circuits and the disc transports via the time multiplex switch to provide highly efficient mass storage and retrieval of messages.

Telephone subscriber line unit with sigma-delta digital to analog converter

Abstract: A digital to analog converter is employed in the digital line circuit of a telephone system and operates to convert a digital signal indicative of an analog speech signal back into a replica of the analog signal. The converter operates with an interpolated input digital signal to detect by means of a sign bit, the characteristic of an input digital word as being indicative of a positive or negative level. An error correcting signal is provided by the converter which is added to the next digital word to provide a compensated word having a sign bit determined by the remainder and the sign bit of the previous digital word. This word is then processed in sequence to produce an output pulse stream from the sign detector indicative of successive positive or negative values as defined by the input digital words, each of which are modified according to the error correcting signal.

Digital radio transmission system

Abstract: A digital radio transmission system for compensating for co-channel or adjacent channel interference or signal level variations and distortions is provided. The system includes apparatus for transmitting a digital signal having a first signal level from a first location to a second remote location, apparatus for monitoring at the second remote location the bit error rate of the received digital signal and apparatus for changing the level of the transmitted digital signal when the received bit error rate is different from a predetermined value.

A monolithic video A/D converter

Abstract: The design and measured performance of a fully parallel monolithic 8-bit A/D converter is reported. The required comparators and combining logic were designed and fabricated with a standard high-performance triple-diffused technology. A bipolar comparator circuit giving good performance with high input impedance is described. Circuit operation is reported at sample rates up to 30 megasamples per second (MS/s), with analog input signal power at frequencies up to 6 MHz. Full 8-bit linearity was achieved. An SNR of 42-44 dB was observed at input signal frequencies up to 5.3 MHz.

Design of a 24-channel transmultiplexer

Abstract: The design of a transmultiplexer capable of performing the bilateral conversion between one 1544 kbit/s digital signal (which represents 24 PCM coded voice channels) and two analog group signals (each one containing 12 voice channels in the 60-108 kHz band) is investigated. It is shown that an FIR filter bank required as part of such a transmultiplexer can be realized efficiently by cascading a discrete cosine transform processor and a weighting network. Fast convolution algorithms are derived for evaluating the cosine transform. A method of using the symmetry conditions to reduce the computation rate in the weighting network and an elegant hardware configuration for implementing it are also discussed.

Device and method for detecting the potential level of the electromagnetic field of a living organism

Abstract: A device and method for detecting the potential level of the electromagnetic field present between a reference point and a test point of a living organism is disclosed. A reference electrode provides a first signal indicative of the potential level of the electromagnetic field at the reference point. A test electrode provides a second signal indicative of the potential level of the electromagnetic field at the test point. More than one test electrode and corresponding second signals can be employed. An analog-to-digital converter responsive to the first and second signals generates a digital signal as a function of the potential difference between the first and second signals. A processor provides an output signal indicative of a parameter or parameters of the living organism as a function of the digital signal. In addition, a low pass filter can be provided ahead of the analog-to-digital converter for filtering out undesired charges and alternating current signals from the first and second signals. The analog-to-digital converter can sample the potential difference between the first and second signals at a desired rate, and the processor can generate the output signal as a function of the digital signal and a stored program. The output signal can provide a diagnostic and predictive function, for example, of the presence or absence of atypical cellular growth, ovarian events, cancer, neurological activity, vitality of seeds, etc.

Digital data link for truck weighing applications

Abstract: An apparatus for communicating a vehicle parameter to a location remote and apart from where the vehicle parameter is measured is disclosed. The apparatus comprises a sensor responsive to the parameter being measured, with the sensor producing an output analog signal proportional to the vehicle parameter being measured. The output analog signal is subsequently converted into a digital signal whereby the vehicle parameter being measured is represented by an N-bit digital code. The N-bit digital code is subsequently transmitted to a location remote and apart from where the vehicle parameter is being measured, and is converted into a continuous analog signal representing the vehicle parameter being measured. The analog signal is subsequently displayed in a viewer usable form. The disclosed apparatus also includes a calibration means which simulates the sensor output analog signal and is switchable therewith to enable end-to-end calibration of the disclosed apparatus.

Decimator apparatus for decreasing the word rate of a digital signal of the type employed in digital telephone systems

Abstract: There is disclosed a decimator structure which incorporates the cascade of an FIR filter with a low pass recursive filter. The input to the decimator is obtained from a high rate analog to digital converter. The output from the decimator is a low rate digital signal having an increased word length. The decimator serves to reduce the word rate and increase the word length of the output digital signal of the analog to digital converter. In this manner, the low rate digital signal at the output of the decimator can be easily accommodated by the telephone system. The decimator described does not require conventional hardware multipliers and hence, affords efficient and economical circuit components which can be implemented by conventional integrated circuit techniques. A register further reduces the pulse rate for transmission.

Self-clocked data transmission system having automatic signal reversing means

Abstract: A two-wire digital data transmission system wherein pairs of binary input signals are encoded into a self-clocked three-level signal. Predetermined start bits and a valid signal are employed in a manner which permits signal reversing to automatically occur at the receiving end so as to provide proper polarity for the received signal.

Three-level, self-clocked data transmission system

Abstract: A serial digital data transmission system wherein pairs of binary input signals are encoded into a self-clocked three-level signal having high, low and intermediate levels for driving over a transmission line with level transitions occurring in response to an applied clock signal, and with a valid signal being employed to indicate data presence. Selectable encoding is provided in response to detecting any accumulated excess of high or low prior transmission levels so as to continually seek maintenance of an intermediate average level for the transmitted signal. The clock and valid signals are regenerated at the receiver for use in deriving the binary signal data from the received three-level signal.

Analytic signal processing in music computation

Abstract: Digital synthesis of music has led to the consideration of models other than the usual additive (Fourier) synthesis of waveforms. One of these methods, based on the FM equation, has been found to be of particular value due to its easy implementation and the richness and evolutionary character of its harmonic structure in time. Any useful synthesis procedure should be accompanied by a corresponding analytic procedure. In this paper we lay the foundations for such a procedure based on the discrete Hilbert transform.

Communications unit for voice and data

Abstract: A communications unit that allows alternate voice and digital data transmissions over a single telephone line. A communications unit, at each of two locations that connect through telephones, includes a trunk signal path that connects to a telephone line and a telephone signal path that connects to the telephone. A digital data signal path connects to digital data processing equipment, usually in the form of an input/output unit in a digital data processing system. A monostable switch interconnects the telephone line and trunk signal paths in a stable conduction to enable voice communications. When the digital data signal path is used, a control automatically shifts the monostable switching means to its astable state thereby to isolate the telephone signal path and to interconnect the trunk signal path and the digital data signal path to allow data communications. When the data communications end, the control automatically allows the switching means to return to its stable state thereby to again enable voice communications. A testing and monitoring unit connects to the telephone signal path, the digital data signal path, and the control means to enable selective testing and monitoring of the communications unit.

Analog to digital converter using timed level changes

Abstract: An analog signal is sampled in response to a sampling command. Each time that the analog signal, or the difference between the analog signal and the previous sample thereof, crosses a respective reference level, a digital signal is produced. Each digital signal consists of a code representing the level crossing or incremental change in level which has occurred and a count representing the time which has elapsed since the last sample command. A digital signal is also produced if the elapsed time reaches a predetermined period. On production of each digital signal, a sampling command is produced and the elapsed time counting is recommenced. The digital signals constitute a digital representation of the analog signal. The converter is particularly useful for converting analog signals having both very high and very low frequency portions, such as current surges which occur on telephone lines affected by lightning (high frequency) and 60 Hz induction (low frequency).

Digital signal/noise ratio amplifier apparatus for a communication system

Abstract: The signal-to-noise ratio of a signal to be transmitted through a communication channel having an upper and lower limit in magnitude is sampled digitally and a common corrective factor for the deviations about the mean value of the signal is determined for amplifying the low portions of the signal without exceeding the limits. By a reverse process at the receiving end of the communication channel, the signal is returned to its original amplitude, thus reducing any noise superposed in the transmission. The invention is applicable to a video channel where the sampled signal is an audio signal. In such case, the deviations of the samples about the mean of the digital information of the audio signal are matched with the mean of the video channel between the black level and the maximum white level.

Apparatus for providing a course correction signal to an electronic automatic pilot to maintain a vessel on a predetermined geographic course

Abstract: A system for controlling the course of a vessel. A digital computer 22 receives information signals from a geographic position locator 20, such as a Loran-C receiver, a depth sounder, or a water temperature sensor, and is also capable of interactive communcations with a remote terminal 24 which is accessible by an operator of the vessel. The digital computer 22 continuously monitors the information signals and develops therefrom a digital output signal representing the sign and magnitude of vessel cross-track error. To obtain information required to determine cross-track error, and to obtain certain other information relating to the identity and type of the geographic position locator 20, the digital computer 22 transmits questions to the remote terminal 24 for display therby and evaluates responses made by the operator through remote terminal 24. The digital computer 22 may be enabled or disabled in response to instructions from the operator using remote terminal 24. The digital computer 22 may also be disabled during the existence of an alarm condition resulting from instability in the information signals, or upon detection of information in the information signals representing loss of tracking by the geographic position locator 20. An interface unit 30, which is enabled only when the digital computer 22 is enabled, converts the cross-track error information in the digital output signal into a corresponding analog cross-track error signal. After suitable amplitude scaling, the analog cross-track error signal is integrated, and the integrated signal is summed with the analog cross-track error signal, to develop a course correction signal which is adapted to be summed with a heading error signal in a conventional electronic automatic pilot, whereby the electronic automatic pilot is capable of maintaining the vessel at a desired heading and on a predetermined geographic track.

Adaptive digital echo cancellation circuit

Abstract: The present invention discloses an adaptive digital echo cancellation circuit including a finite impulse response digital filter, wherein the digital filter coefficients are adapted by continuous updating to compensate for telephone subscriber line echo conditions to enable the digital filter to continuously simulate the instantaneous subscriber line echo. The continuous coefficient update is provided by a correlator which includes provision for introducing non-linearities into the PCM transmitted and received signals, in parallel with the speech path, to derive a simplified digital representation of the PCM speech, thereby reducing the signal processing hardware required by the correlator to derive the updated filter coefficients.

A new delayed action electrical protection device, depending on an adjusted magnitude

Abstract: This invention provides a delayed action electrical protection device which may be used for example to protect electrical lines and equipment against disturbances such as overload conditions and minimum voltage conditions. An analogue signal denoting the particular condition for which protection is to be provided is converted into a digital signal which is applied to a micro-processor. In the micro-processor this digital is compared with a prescribed value or values fed into the processor. The processor contains information relating to characteristic curves which define the time delay between the detection of a particular condition and the production of a tripping signal which may. for example, be used to interrupt the electrical circuit and/or provide an alarm. The time delay varies inversely with the magnitude of any disturbance and may, for example, be defined by the expression:- where K is a constant; i equals ; where I is the measur- ad current and In is the prescribed value.

Digital input apparatus

Abstract: A digital input apparatus is provided which is used as an input apparatus for a digital signal processor and can eliminate noise components resulting from electromagnetic induction and resulting from chattering which is produced by the opening or closing of a contact. One input signal outputted from the multiplexer (105) is applied through a latch flip-flop (108) to a counter (114) used on a time sharing basis so that counting is effected. Individual counts corresponding to a plurality of input signals are stored in a memory (117). When a count becomes all "1's" or "0's", the counter (114) produces a carry signal or a borrow signal supplied to a J-K flip-flop (113). The J-K flip-flop (113) produces an input signal of a predetermined waveform free from noise components.

Filter and system incorporating the filter for processing discrete samples of composite signals

Abstract: A system for processing discrete digitized samples representing composite signals utilizing a filter which eliminates a periodic signal component from the composite signal. The filter receives and stores consecutive digital sample representations of the composite signal and, for each received sample representation, provides a digital average representation of the values of a selected number of the received digital sample representations which define a zero average value of the periodic signal component. In one embodiment of the signal processing system, the filter is arranged in circuit with digital delays and digital signal combining and differencing circuits to form a digital color television signal dropout compensator, which is adaptable for use in NTSC, PAL, PAL-M, or other television standard systems. In a dropout compensator adapted for NTSC color television signals, the filter receives the digital composite television signal and eliminates the chrominance component therefrom, leaving only the luminance component at its output. A following digital subtractor is coupled to subtract the luminance component provided by the filter from the received digital composite television signal and provide the chrominance component at its output. The separated chrominance component is phase adjusted on consecutive television lines and recombined with the separated luminance component provided by the filter for substitution in the television signal in place of the dropout affected portion thereof. The dropout compensator also includes a digital delay of one horizontal line period through which the television signal components are passed to provide the delay necessary for substituting television signal information from a prior horizontal line.

Digital signal detector

Abstract: A digital signal detector is disclosed that detects a serial bit stream transmitted at a predetermined bit frequency. Bit transistors are totalized in a counter (115) over a predetermined time interval. Bit transistions occurring during a good window interval from gate (111) increment the totalized count by one. Bit transistions occurring during a bad window interval from gate (112) decrement the totalized count by one. Bit transistions occurring during a marginal window interval from gate (110), situated between the good and bad window intervals, do not affect the totalized count. If the counter (115) reaches a predetermined count during the time interval, a detect signal is provided by flip flop (117) indicating that the digital signal has been detected. The counter (115) can be further loaded with a threshold count for tailoring the digital signal detector for operation at a particular signal-to-noise ratio. Periodic signals that have frequencies that are submultiples of the bit frequency are detected by correlating the digital signal between two predetermined stages of a shift register (101). The digital signal detector may provide a detector output signal when both the digital signal is detected atflip flop (117) and periodic signals having submultiple frequencies are not present at flip flop 106).

Glassware forming machine computer-ram controller system

Abstract: A programmable automatic controller for operating a section of a glassware forming machine having a plurality of components which operate in a timed or sequential relationship with one another. The controller includes a timing means for generating a digital signal in synchronism with the operation of the machine, wherein the digital signal provides an instantaneous indication of the time elapsed in each cycle of operation of the machine. A random access memory (RAM) stores the status of every section component at each increment of time during each cycle of machine operation. The digital signal addresses the RAM so that the statuses of all components for the corresponding time are directed to drivers which provide component enable or inhibit command signals. Control means for adjusting the actuation and deactuation times of the section components provide information of a computer which updates an internal memory table organized similarly to the RAM. The computer also controls the transfer of data from the internal table to the RAM in such a way that the data updating speed of the control computer is independent of the machine cycle speed.

Recursive-type digital filter

Abstract: OF THE DISCLOSURE A recursive type digital filter receiving a digital input signal x(n) having a plurality of bits and delivering a digital output signal y(n) satisfying the following equation, , where n indicates a natural number, M and N orders of time lag in the signal transference, ak and bk coefficients defined by a filter characteristic, aMand bN being coefficients which are not equal to zero, comprises an output control circuit for delivering a digital signal indicating a positive or negative limit value in place of the digital output signal y(n) when the amplitude of the signal y(n) exceeds an allowable value. In combination with this output control circuit, the filter also utilizes a feedback signal for calculation purposes which feedback signal has its amplitude reduced from that of y(n) by a predetermined ratio. Further, an arrangement is provided for clearing registers of filter when necessary to prevent overflow oscillation.

Laser beam recording system

Abstract: In a laser beam recording system employing a rotating polygonal mirror for deflecting a recording light beam and a read-out light beam for synchronization, a linear encoder is used to generate a video clock signal in synchronization with the photoelectric pulse signal obtained through the linear encoder. In the video clock signal generator, a clock signal is divided into 1/n where n is an integral number to provide a reference pulse signal to be compared with the photoelectric pulse signal. The displacement of the phase of the photoelectric pulse signal from the reference pulse signal is detected and is corrected by a phase comparator. Thus, a video clock signal having a frequency of n-times as large as that of the photoelectric pulse signal is generated.