Abstract: A cable television upstream data transmission system provides a plurality of time slots synchronized to the downstream symbol clock for use by subscriber terminals in upstream data transmission. The width and number of time slots are controlled by a pair of downloadable values to accommodate dynamic changes of the cable system. A transmission modulator used within the subscriber terminal produces an upstream transmission carrier having a frequency locked to the symbol clock. The frequency of the carrier signal produced by the transmission modulator is programmably controlled by a plurality of program values which are selected to provide frequency and phase lock of the modulator's carrier to the symbol clock.

Abstract: A dual HDTV/NTSC receiver includes a microprocessor for controlling a tuner for synthesizing the carrier frequencies of HDTV signals and NTSC signals. The HDTV signals are inherently of much lower power than the NTSC signals. The tuner initially synthesizes the carrier frequency of a desired HDTV signal which is attempted to be detected in an narrow band synchronous detector. Detection of the HDTV signal produces a high lock detect signal which causes the microprocessor to enable an HDTV processing channel. If no HDTV signal is detected, the lock detect signal remains low and the microprocessor controls the tuner for synthesizing the carrier frequency of the NTSC co-channel television signal. A high lock detect signal from the narrow band synchronous detector, indicating detection of the NTSC co-channel causes the microprocessor to enable the NTSC processing channel. A system for automatically programming the receiver and memorizing which type signal is present on each television channel is also shown.

Abstract: A housekeeping manifold is provided at the end of a row of ejector apertures of a drop-on-demand printhead module. The housekeeping manifold includes upper and lower parts disposed on opposite sides of the row of ejector apertures, a trench extending between the manifold parts through which ink drops from the ejector apertures are discharged, openings between the manifold parts and the trench and a ducting arrangement for supplying environmental fluids to or exhausting such fluids from the region of said apertures by way of the manifold parts and trench.

Abstract: A drop-on-demand ink drop printhead is mounted fixed in a printer for selectively printing drops of ink in a print line. The printhead comprises a plurality of stacks of like print modules arranged in side-by-side relationship to form a number of laterally offset module layers. Each of the modules includes at least one group of uniformly laterally spaced ink ejectors, the groups in each layer being laterally spaced by the same amount such that drops from overlapping portions of two or more of the groups interleave to form a segment of the print line. Make-up ink and air supply ducting arrangements are provided for the modules in each stack.

Abstract: An electronic musical instrument includes first and second control switches for initiating chorus and verse break patterns in an automatic accompaniment arrangement. A chorus accompaniment pattern is automatically generated following the chorus break pattern and a verse accompaniment pattern is automatically generated following the verse break pattern, regardless of the pattern types generated prior to the breaks. The generation of breaks are inhibited during the last 1/4 interval of a bar and during the generation of the introduction and ending portions of the accompaniment arrangement.

Abstract: An abrasive multi-disc cutter is formed by uniformly coating a cylindrical holder with a mixture of diamond powder and resin. The holder is rotated about its longitudinal axis while one or more beams of laser energy are used to ablate the resin for forming a plurality of annular depressions in the coating, the depressions being equally spaced along the longitudinal axis of the cylindrical holder. An abrasive annular cutting disc is thereby provided between each pair of successive annular depressions. The cutter is used to cut a plurality of parallel, spaced ink cavities in a piezoelectric substrate forming part of an ink jet printer printhead.

Abstract: A pulsed droplet ink jet printer has relatively long thin ink channels extending in parallel between an ink manifold 13, and a nozzle plate 5 providing a nozzle 6 for each channel. Side walls 11 may be formed substantially entirely of piezo-electric material so as to be displaceable transversely into a selected channel on the application of an electric field. This transverse displacement produces an acoustic wave in the channel which results in the ejection of an ink droplet. The side walls may deflect in shear mode to a cross-section of chevron formation. Usefully, it is arranged that both side walls adjoining the selected channel are displaced inwardly of the channel to cooperate in droplet ejection. Under this arrangement, the channels are assigned alternately to first and second groups of channels, only one group of channels being capable of actuation at any one instant.

Abstract: A pulsed droplet ink jet printer has at least one channel communicating with a nozzle. The side wall of the channel is formed as a shear mode piezo-electric actuator. Electrodes applied to the actuator enable an electric field to be applied such that the actuator moves in the direction of the field to change the liquid pressure in the channel and thereby eject a droplet through the nozzle. The actuator can be made in two parts so as to deform, in cross section, to a chevron formation.

Abstract: A multichannel communications receiver, e.g. a CATV converter, includes a switched filter for reducing third order intermodulation distortion by limiting the number of channels processed by the receiver. In a preferred embodiment, the filter is switchable between a highpass and a lowpass configuration by a control signal supplied to two switching diodes. The input and output of the filter are coupled by a mutual inductance which partially compensates for the effect of parasitic inductance at higher frequencies.

Abstract: A television receiver comprises a television system energized by the powerlines of a commercial power grid, a telephone network access system including a microphone disposed in close proximity with the audio speaker of the television system and a remote control system enabling the receiver to be operated in a television mode or a telephone mode. The television receiver according to the invention is characterized by having an annunciator/intercom enabled for operation by the remote control system. In the annunciator mode, the audio section of the television system is disabled and the microphone is connected through a radio-frequency signal transmitter to the power lines for generating a radio-frequency signal for local transmission. A frequency-modulator is included for modulating the radio frequency signal.

Abstract: A decoder is responsive to a decode authorization signal for unscrambling a broadcast RF television signal having randomly suppressed horizontal blanking and synchronization pulses. The decoder comprises a tuner having a gated automatic gain control circuit and a video detector responsive thereto for developing a baseband video signal corresponding to the broadcast television signal. The decoder further comprises a sync restoration circuit developing a standard horizontal synchronization pulse in response to each suppressed horizontal blanking pulse of the baseband video signal, the standard horizontal synchronization pulses being continuously combined with the baseband video signal for operating the automatic gain control circuit and being coupled for unscrambling the baseband video signal only in response to the decode authorization signal.

Abstract: A protection circuit for a switching regulator power supply comprises a series-pass transistor having a collector-emitter circuit connected between a source of DC operating potential and the power supply. A bootstrap signal developed by the power supply and having a voltage level greater than the potential of the DC source is fed back to the base of the series-pass transistor for rendering the transistor fully conductive under normal operating conditions and to improve performance under marginally low levels of the DC source. A reverse biased diode is connected between the base of the series-pass transistor and the DC source to limit the transistor's base drive via the feedback path to a safe level. A shunting transistor is responsive to an overvoltage condition of the DC source for reducing the base drive of the series-pass transistor to limit the DC potential supplied to the power supply to a safe level.

Abstract: A pair of elongate rail members are secured along opposed edges of a printed circuit board for protecting the solder fillets formed on the foil side of the board and to facilitate convenient screwless mounting of the printed circuit board to a substantially flat platform of a television receiver chassis or the like. Each rail member comprises a printed circuit board supporting surface and a substantially flat base adapted for mounting on the platform, the base being spaced from the supporting surface by a distance greater than the length of the solder fillets. The rail members are secured to the printed circuit board by resilient tabs which snap lock the foil surface of the board in abutment with the supporting surface. At least one locking member depends from the base of each rail and is received for limited longitudinal movement within an elongate slot formed in the platform, the locking members and base forming a bite for capturing an edge of the platform at one limit of longitudinal movement.

Abstract: A television signal processing apparatus is responsive to a received television signal for translating the frequency spectrum thereof to a frequency band characterized by a fixed frequency carrier signal frequency modulated in accordance with a baseband audio signal. The frequency modulated carrier signal is combined with an unmodulated CW muting signal having a frequency approximately equal to the frequency of the carrier signal to facilitate remotely controlled muting of the baseband audio signal in accordance with the FM capture effect.

Abstract: A teletext interface is coupled between a television receiver and a medium storing a plurality of digitally encoded signals each representing a selected text/graphics character intended for transmission as a corresponding synthetic video signal during the active scanning intervals of a television signal. The teletext interface includes a ROM for converting each of the digitally encoded signals to a teletext encoded signal representing a corresponding text/graphics character and apparatus for inserting the teletext encoded signals as a plurality of teletext formated data rows in successive teletext lines of the television signal. A television receiver including a built-in teletext decoder is responsive to the teletext formated data rows for displaying the selected text/graphics characters in a high quality form while a standard receiver is responsive to the synthetic video signal for displaying the characters in a poorer quality form.

Abstract: A teletext communications system includes a transmitter cyclically transmitting a plurality of conventional teletext encoded data rows together with one or more teletext encoded special services data rows. A plurality of teletext decoder equipped receivers are operable for acquiring the conventional teletext rows but not the special services rows. Subscribers to the special services data are provided with data decoders responsive to the cyclical transmissions for acquiring only the special services data rows, the data decoders including apparatus for storing the data encoded in an acquired special services data row and for providing a display of the information represented thereby.

Abstract: A teletext communications system comprises a transmitter, e.g. an orbiting satellite, transmitting multiple pages of a teletext encoded data service at selected times of the day, each teletext page including a first non-displayable auxiliary teletext data row defining a selected time interval and a unique page memory address code. The transmitter also continuously transmits a second non-displayable auxiliary teletext data row including a time of day code. A teletext decoder is adapted for acquiring and storing each transmitted teletext page at a page memory defined by said page memory address code and automatically rebroadcasts each of the stored pages for which the stored selected time interval coincides with the transmitted time of day code.

Abstract: A color control circuit for selectively modifying the red, green and blue color signals developed at the output of a teletext-type decoder comprises a common input stage responsive to the teletext decoder for developing a bi-level control voltage identifying the portions of the color signals representing background and foreground display information. Each color signal is coupled to a respective output stage which causes the associated color signal to assume a first intensity level in response to the control voltage being at its first level and a second intensity level greater than the first intensity level in response to the control voltage being at its second level. As a result, background colors are displayed at a reduced contrast level relative to foreground colors. In addition, selected single color foreground information may be displayed at a further increased intensity level to improve the readability of the display.

Abstract: An automatic beam current limiting circuit for a color television receiver comprises means for individually monitoring the three cathode currents developed in response to the green, blue and red video drive signals. The video processing unit of the receiver is automatically adjusted in response to any one of the cathode currents exceeding a predetermined level for reducing the video drive signals to limit the excessive cathode current to the predetermined level. As a result, the individual cathode currents are limited to the predetermined level while the combined cathode currents are allowed to substantially exceed this level.

Abstract: A tuning system is described for use with a television receiver which has channel selection keys on a keyboard for selecting a desired television channel. The system employs a frequency synthesizer for tuning the receiver's local oscillator to a selected television channel. For fine tuning, the system employs a fine tuning key which doubles as a channel selection key. Actuation of this key places the system in a fine tuning mode, and a logic circuit responds to actuation of a channel-up or channel-down key for causing the receiver to be fine tuned in the selected direction. In the preferred embodiment, fine tuning and channel selection are controlled by the logic circuit so as to occur during the receiver's vertical interval to eliminate digital switching noise from the receiver's image.