Abstract: A frequency synthesizer having a frequency-locked loop providing any digitally selected output frequency, and means to frequency modulate the selected output frequency at an audio rate. The frequency-locked loop includes a frequency-to-current converter coupled to the output of a voltage-controlled oscillator to provide a current, representing the actual frequency of the oscillator, which is compared with a current representing a desired output frequency. A resulting error signal controls the oscillator center frequency, which can be frequency modulated by an audio-frequency signal.

Abstract: When two color television signals are transmitted over a common non-linear path, such as a transponder in a communications satellite, the two color subcarriers at slightly different frequencies intermodulate each other and produce a disturbing flickering of color on the screens of monitors and receivers. The crosstalk is made invisible in the present system by translating the flicker to fluctuations occurring at too high a frequency to be seen. At the transmitting terminal, alternate lines of one of the television video signals are delayed by half the period of the color subcarrier, and at the receiving terminal, intermediate lines of the same television video signal are delayed by half the period of the subcarrier. The fluctuations may be made invisible to signal-monitoring instruments by passing both the delayed and undelayed television video signals through chroma averaging circuits at the receiving terminal.

Abstract: An error detection and correction system in which at least the highest order bit of each data word is given a greater protection against errors in transmission than lower order bits. Useful for digitized TV signals where errors in received high order bits have much worse effect on picture quality than errors in low order bits. A parity is generated for each data word in accordance with a self-orthogonal convolutional code constructed by the use of the base elements of a difference triangle for each bit of the data word, the difference triangles being disjoint, the triangle associated with the highest order bit or bits having a large number or numbers of base elements, and the triangles associated with the lowest order protected bit or bits consisting of a single base element. Errors in received code words are detected and corrected in a decoder including majority logic threshold detectors. Error correcting feedback to the syndrome shift register is limited to errors detected in the high order bits.

Abstract: An error detection and correction system in which at least the highest order bit of each data word is given a greater protection against errors in transmission than lower order bits. Useful for digitized TV signals where errors in received high order bits have much worse effect on picture quality than errors in low order bits. A parity is generated for each data word in accordance with a self-orthogonal convolutional code constructed by the use of the base elements of a difference triangle for each bit of the data word, the difference triangles being disjoint, the triangle associated with the highest order bit or bits having a large number or numbers of base elements, and the triangles associated with the lowest order protected bit or bits consisting of a single base element. Errors in received code words are detected and corrected in a decoder including majority logic threshold detectors.

Abstract: A channel switching system useful in a satellite for amplifying some or all of three different RF frequency-band channel signals in two traveling wave tube amplifiers and transmitting the signals via two spot antennas to two regions on earth. Two signals are normally amplified in the two amplifiers and directed to the two regions on earth. A third frequency channel signal can be simultaneously applied through one or the other of the two paths. If an amplifier fails, the third frequency channel can be directed through the remaining operative amplifier to either one of the two regions on earth.

Abstract: A token for use in a vending machine consists of a plastic card having at least one pair of side-by-side holograms embossed thereon. A token reader includes means to guide a token into the path of a readout beam. When two photodetectors positioned at predetermined spaced locations receive equal-amplitude first order beams from an illuminated pair of holograms, an electrically-operated plunger in the token reader operates to obliterate the pair of holograms on the token, and then a signal from a third photodetector in the token reader enables an output signal for operating the vending machine.

Abstract: A phase and frequency detector includes a first flip-flop triggered by a pulse wave from a reference source, and a second flip-flop triggered by a pulse wave from a voltage-controlled oscillator. Gate means couple outputs of the flip-flops back to reset inputs of the flip-flops so that one of the flip-flops generates pulses having widths proportional to the phase difference of the first and second pulse waves. The gate means inhibits the resetting of the triggered flip-flop when the pulses of the first and second pulse waves do not overlap, so that the triggered flip-flop then generates a continuous output useful for rapidly correcting the frequency of the voltage-controlled oscillator.

Abstract: A converter to translate a sampled color television video signal, consisting of four pulse-code-modulated 8-bit digital samples during each cycle of the color subcarrier, to a corresponding signal consisting of three pulse-code-modulated 8-bit digital samples during each cycle of the color subcarrier. The four 8-bit samples from present and preceeding cycles are stored in several 8-bit input registers. The 8-bit sample in one of the input registers is coupled to an output register once per cycle. Two predetermined weighted combinations of 8-bit samples in predetermined ones of the input registers are coupled to second and third output registers once per cycle.

Abstract: A frequency synthesizer capable of rapidly changing to a different desired output frequency includes a voltage-controlled oscillator and a variable frequency divider arranged in a phase-locked loop. A first frequency-control voltage is initially applied to the voltage-controlled oscillator to cause a rapid change in its output frequency toward a desired value. Then, the divisor of the variable frequency divider is changed to produce a second frequency-control voltage which precisely sets and maintains the oscillator output frequency at the desired value.

Abstract: A deflection-type modulator, for insertion in the path of a laser beam directed to a remote receiver, includes a mirror mounted on a voice coil device and positioned in the focal plane of a lens. A prism reflects the laser beam at right angles through one-half of the lens to a focal point on the mirror. The beam is reflected back through the other half of the lens, and is reflected by another face of the prism normally to a point between two spaced photosensors at the remote receiver. An electrical audio signal applied to the voice coil device causes the laser beam to be deflected back and forth between the two photosensors at the remote receiver.

Abstract: A scanner for reading binary digit spots on a transparent film includes a laser light beam which is directed through a beam splitter and through the film to a mirror, from which it is reflected back through the film to illuminate a small area on the film. Light which is not blocked by a recorded spot on the film continues back to the beam splitter, from which the beam is directed to a photodetector. The photodetector is positioned to receive light from solely a portion of the illuminated area of the film, to provide high definition scanning not adversely affected by distortion of the illuminating light beam by imperfections in the film and mirror.

Abstract: Serial data is scrambled at a transmitting terminal by storing it in sequential locations in a first random access memory, while previously stored information is read out of a second random access memory using a pseudo-random address counter. Whenever one memory is filled and the other memory is emptied, the roles of the memories are transposed. Similar apparatus at a receiving terminal is operated in synchronism and phase to unscramble the received data.

Abstract: An automobile is constructed so that switching between free wheeling and direct drive is accomplished automatically, using normal driver reflexes, by causing free wheeling to be initiated (or continued) whenever the automobile is accelerated, and direct drive to be initiated (or continued) whenever the automobile is braked.

Abstract: An optical scanner is disclosed for scanning a three-dimensional object or a two-dimensional document located in a space which is open and exposed to ambient light. Light from a laser is directed through a beam splitter and a deflector to the object or document, from which it is reflected back through the deflector, and from the beam splitter through a narrow-band optical interference filter to a photodetector. The laser light is modulated at a carrier frequency rate, and the electrical signal from the photodetector is demodulated to produce a video signal free of disturbances due to ambient light.

Abstract: A circuit for protecting a TELEX line driver from damage due to overcurrent caused by a short circuit on the communications line. Two transistors are connected to form a monostable circuit having an input coupled across a resistor in the current path of the line driver. When current in the line driver exceeds a safe threshold value, the monostable circuit is triggered into a relatively long timed state during which the output of the monostable circuit inhibits conduction in the line driver. When the monostable circuit returns to its stable state, the line driver conducts for a short time until the monostable circuit is again triggered. Conduction in the line driver has a protective low duty cycle until the short circuit is removed and normal operation is automatically resumed.

Abstract: A delta modulation system for generating a digital output signal representative of an analog input signal. The analog input signal is periodically compared to an analog feedback signal to generate the digital output signal. The analog feedback signal is generated from the digital output signal by generating a signal having an amplitude indicative of the absolute value of the derivative of the analog input signal, multiplying such absolute value signal by the digital output signal and integrating the product signal.

Abstract: A data communications or distribution loop has a plurality of computer stations each of which introduces a delay while it examines the header of each circulating packet or block of data. An elastic synchronizing buffer, including a random-access memory, is included in the loop to introduce a delay which, when added to the delays introduced by the stations, equals the period of a packet. The delay introduced by the buffer is automatically adjusted as stations are added to, or removed from, the loop.

Abstract: The relative compression in the cylinders of an internal combustion engine is tested by analyzing the starter motor current waveform when the engine is cranked with the ignition or the fuel inhibited. In asymmetrical engines, where the compression strokes of individual cylinders are unequally spaced in time, the starter current waveform may contain double-hump cycles. The area under each double-hump cycle is integrated, and the integration peaks are compared. The compression in one or more cylinders is deficient if the minimum integration peak is less than the maximum integration peak by a significant percentage such as 15 percent or more.

Abstract: A signal-frequency tracking band-pass filter useful for passing an input signal which changes rapidly in frequency. The tracking filter includes a voltage-controlled band pass filter, and a frequency-to-voltage converter for translating the output frequency of the filter to a voltage for controlling the pass band center frequency of the filter. The Q of the filter is controlled by a feedback circuit which makes the Q vary inversely with output signal amplitude. The Q is high for weak signals that are hard to lock on to, and the Q is low for strong signals to facilitate tracking of signals which change rapidly in frequency. The filter is especially useful for inclusion in internal combustion engine diagnostic equipment.

Abstract: A converter, for converting a dual-tone multi-frequency (DTMF) signal produced by a TOUCH-TONE telephone to a 2-out-of-7 coded representation of the "dialed" number, includes an oscillator having a frequency much higher than the frequencies of the tones, a high band circuit for high band tone frequencies, and a low band circuit for low band tone frequencies. Each circuit includes a filter for passing the respective band of tone frequencies from an input terminal, a limiter for translating a received tone sine wave passed by the filter to a corresponding square wave, a counter, a switch enabled by the square wave output of the limiter for coupling the output of the oscillator to the input of the counter during a cycle of the square wave from the limiter, and a decoder for translating the resulting count in the counter to a signal on an output line representing one of the tone frequencies.