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: In a surface acoustic wave filter which employs a multi-strip coupler to offset the acoustic wave path, diffraction effects lead to spurious responses at a filter trap frequency. The diffracted wavefronts are curved, instead of being straight and parallel to the transducer fingers as are the wavefronts of the strip-coupled acoustic signal. Thus an additional transducer is employed which has fingers slanted at the same angle as the local wavefronts of the diffracted acoustic energy. The resulting parallel relationship permits the additional transducer to be designed so that it compensates for the undesired trap frequency response by producing an equal magnitude, oppositely phased trap frequency output. In order to conserve substrate area, a technique is disclosed for locating the compensating transducer within a dummy area of an apodized main receiving transducer.

Abstract: An article of manufacture is disclosed for use in a projection television system. A cathode ray picture tube has a face panel with a rearwardly extending skirt and a window for receiving a cathodoluminescent imaging screen. The tube has a seal land which defines a plane whose normal makes a non-zero acute angle with respect to the axis of said window. The article is for use in a system having a cathode ray picture tube whose projection optical axis is on the axis of a remotely located viewing screen, and at least one displaced axis cathode ray picture tube; that is, a tube whose projection optical axis is displaced from the axis of the viewing screen by a non-zero acute angle.

Abstract: In order to suppress triple transit ghost images in a T.V. receiver, a surface wave acoustic filter is provided in which either the input or output transducer system, or both, includes both primary and dummy transducers, the echoes from which cancel each other totally. The dummy transducer is designed as a function not only of position along the acoustic beam path, but also as a function of the number of elemental transducers and their interdigitated lengths; and the design also takes into account relevant electrical parameters including transducer admittances and any external or parasitic impedances under short circuit and open circuit conditions. These factors are taken into account not only for the primary transducer, but also for the dummy transducer.

Abstract: A low-cost, deeply filtered television imge display is depicted. A viewing screen includes a patterned layer of phosphor particles disposed contiguous to the inner surface of the display. The layer when excited emits light of a predetermined color. The display includes means for exciting selected areas of the layer to produce a luminescent informational image. The image is subject to loss of contrast caused by reflection of ambient light from the layer. The improvement comprises a shallow, random, clumped, discontinuous, open dispersion of contrast-enhancing particles of pigment having a body color corresponding generally to the predetermined color disposed directly on the viewing screen beneath the layer and not significantly admixed with the phosphor particles. The percentage of open area of the dispersion of pigment particles and the absorption characteristics thereof are such that the dispersion efficiently filters ambient light at its interface with the layer.

Abstract: An integratable CRT spot cut-off network is described for use in a television receiver. The network establishes a reference current for biasing up the receiver's G.sub.1 grid when the supply voltage comes up, and a bypass capacitor coupled to the grid charges toward the supply voltage. When the receiver is turned off, the network terminates the reference current as the supply voltage starts to collapse and prevents the bypass capacitor from discharging. The charge stored on the capacitor reverse biases the grid to cut off the receiver's beam current.

Abstract: Means are disclosed for use in a line printer having a print head on a carriage traversing parallel to a platen for printing characters through an inked ribbon onto a print medium drawn between the ribbon and platen. The inventive means provide for adjusting the print head position. Bracket means slidably mounted on the carriage provide for movement of the bracket toward and away from the platen. The bracket provides for mounting the print head on the carriage. A bracket adjusting member consisting of a lever in the preferred embodiment is coupled between the carriage and the bracket for manual adjustment of the spacing of the print head with respect to the platen. Pointer means are pivotally mounted on the carriage engage the bracket such that bracket movement and hence print head movement is translated into pointer movment, providing for a gross indication by means of indicia beneath the pointer of print head location with respect to the platen.

Abstract: Heat sink means for a projection television cathode ray picture are disclosed. The tube has a face plate on the inner surface of which is deposited a cathodoluminescent screen for forming a television image. The face plate develops an undesirably high temperature during operation resulting in cracking. The heat sink means according to the invention comprises a heat-conductive panel, which may be a metallic plate, larger in area than the face panel. The panel has a window for passing the television image. The panel is in intimate contact with the face plate for conducting heat from the face plate and inhibiting thermal cracking.

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: A one-piece, directly heated cathode is disclosed for use in a cathode ray tube electron gun. The cathode according to the invention has the configuration of a hollow cylinder with one closed end for receiving a thermionic electron-emissive coating. A pair of body portions extending axially in the same direction from diametrically opposed sides of the closed end define two legs which act as serial electrical conductors having inherent resistance for use in resistively heating the electron-emissive coating. The legs have an arcuate cross-section effective to structurally stabilize the cathode and suppress temperature-induced lateral displacement of the cathode which would otherwise degrade the performance of the electron gun.

Abstract: A single-sheet (i.e. two-surface) rear projection screen for television applications is described, in which the front or viewer-facing surface is formed with vertically running lenticules for horizontal image light distribution and the rear or projector-facing surface is formed with horizontally running lenticules for vertical image light distribution. There is no need for a diffuser. The lenticule profiles on both surfaces vary as a function of distance from the projection axis in a manner calculated to accomplish several optical objectives: collimation, cosine power fall-off compensation, and rearward reflection gradient compensation. Computer programs for calculating the profiles are disclosed.

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 high voltage disconnect plug and a receptacle therefor are described for use in coupling a high voltage conductor to a load such as a CRT. The plug includes a lock nut and a deformable annular ring through which the conductor passes, and a hollow sleeve which slides over the conductor to capture the ring between the sleeve and the lock nut. A spring carried by the sleeve engages a contact on an end of the conductor which passes through the sleeve. Insertion of the plug into a bore in the receptacle compresses the spring between the conductor's contact and a high voltage contact in the bore for coupling high voltage to the latter contact. Locking the nut to the receptacle deforms the ring to tightly seal it against the receptacle's inner wall around the bore.

Abstract: An article of manufacture comprising a cathode ray tube is disclosed for use in a projection television system. The tube has a funnel and a face panel with a window for receiving a rectangular imaging screen. The projection television system includes tube receptacle means having conjugate means for accepting the tube in proper rotational alignment. The tube according to the invention is characterized by having two pairs of substantially radially oriented embossments on the funnel. The embossments are centered on, and azimuthally spaced one hundred and eighty degrees apart, on a diametrical line about forty-five degrees in counterclockwise rotation with respect to the minor axis of the rectangular imaging screen. The pairs of embossments according to the invention provide for engagement with the conjugate means of the tube receptacle means for proper rotational alignment of the tube in the system.

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.

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: Optical mirror adjustment means are disclosed for use in a projection television system having a rear projection viewing screen. The means according to the invention provide for adjusting the reflecting angles of a mirror reflecting an aerial image of a projected television image onto the screen. Pivot means provide for tilting the mirror in elevation, and screw means provide for positionally adjusting and fixing the mirror in a desired elevation angle. Screw means attached to the pivot means provide for positioning and fixing the mirror as azimuthally. The optical mirror adjustment means are such that the mirror can be adjusted to reflect the aerial image in precise coincidence onto the viewing screen.

Abstract: Unitary optical assembly means is disclosed for use in an ultra-compact projection television receiver. The unitary optical assembly means is selectively storable in the receiver cabinet and elevatable therefrom by precision elevating means. The receiver includes a stationary optical assembly means permanently enclosed in the lower portion of the cabinet for forming a television image and projecting, when the unitary optical assembly is elevated an aerial image of the television image upwardly a predetermined image projection distance along an optical path folded by optical path folding means. The unitary optical assembly comprises in combination mirror means arranged at a predetermined angle effective to receive the aerial image and reflect the image forwardly. The unitary optical assembly also comprises rear projection screen means located at the terminus of the optical path and vertically arranged for receiving said aerial image reflected by the mirror means for displaying the image.

Abstract: An apparatus is disclosed for the positive retention of a closure panel alternately in an open position or a closed position with respect to a compartment. The apparatus comprises push rod means, crank pin means for rotatively capturing an end of the push rod means, and resilient pocket means cupped in an adjacent inner wall of the compartment for receiving the distal end of the push rod means. The effect according to the invention is such that as the panel is alternately opened or closed, the intermittent rotary-to-reciprocal motion of the crank pin/push rod means causes the crank pin means to rotate past the dead center of the pivot means against the restorative force of the resilient pocket. The subsequent contraction of the pocket provides for positive retention of the closure panel in an open or closed position.