Abstract: A color cathode ray tube is depicted which has a faceplate and a shadow mask mounted in precise relationship to the faceplate by a plurality of suspension devices spaced on the periphery of the faceplate. The suspension devices provide for rigidly and stably suspending the mask. Each suspension device comprises a stud extending from the faceplate and a leaf spring formed to support and space the mask in proper relationship to the faceplate with the spring having a first end formed for detachable engagement to the stud. A bracket or frame attached to the mask has a seat for receiving in permanent attachment the second end of the spring. The suspension device is characterized by the spring and bracket or frame having configurations at their interface which are such that the lateral edges of the spring are compressively preloaded against the bracket or frame to provide a wide stance, which enhances the stability of the suspension of said mask in relation to said faceplate.

Abstract: A television receiver includes a frequency synthesizer phase lock loop operated in a time multiplexed manner to provide two tuning signals for tuning a received television signal. The two tuning signals are developed at the outputs of first and second voltage controlled local oscillators alternately operated in response to a phase detector which is reset at the beginning of each alternate operation.

Abstract: A color demodulation and comb filtering system is described for use in a color television receiver. The system includes a pair of charge coupled devices (CCD's) which each receive a filtered video signal and which develop outputs which are delayed, one from the other, by one horizontal line interval. Both devices are clocked at the color subcarrier frequency to develop outputs which include demodulated color and luminance components. The outputs of the two CCD's are combined in a summer, the output of which includes demodulated color components from which luminance components are eliminated.

Abstract: An integratable vertical sync separator is described for use in a television receiver. The preferred embodiment includes an integrated capacitor which is charged and alternately discharged by current sources in response to composite sync pulses such that the capacitor develops a relatively high level voltage when vertical sync pulses are received. The voltage developed by the capacitor is sensed by a peak detector for developing a vertical sync output pulse and for producing a feedback signal indicative of the amplitude of the relatively high level voltage on the capacitor. The feedback signal is applied to the current sources which are conditioned to vary the charge and discharge rates of the capacitor for improved performance in sub-standard signal conditions.

Abstract: An AFC circuit for a television system having stereophonic sound is disclosed. In response to a channel change, which causes a significant change in the level of the AFC error signal, the error signal is coupled substantially without modification to the local oscillator control terminal and the sound is muted. After an interval sufficient to permit frequency lock to be achieved the error signal is then coupled to the oscillator through a low pass filter and the muting operation is terminated.

Abstract: A service switch arrangement for a color television receiver having a low level matrixing system developing red, blue and green color signals includes a service switch having a normal position and a service position. In the normal position of the switch, a video output amplifier is enabled for coupling the red, blue and green color signals to the electron gun cathode elements of a color cathode ray tube. In the service position of the switch, the video output amplifier is disabled while an independently generated DC control voltage is coupled to the electron gun cathode elements for facilitating adjustment of the cut-off points of the cathode elements.

Abstract: A CCD comb filter and color demodulation system is described for use in a color television receiver. The system includes a CCD comb filter receiving a video signal having interleaved luminance and color components, the latter components including a color subcarrier at a nominal frequency. Preferably, the comb filter includes but two CCD devices which receive the input video signal and apply their sampled outputs to a summer to develop combed luminance components and combed color components which occupy different frequency bands. The combed color components include a color subcarrier and sidebands which are translated upward in frequency by a given multiple of the nominal subcarrier frequency. The latter components are applied to a pair of CCD output filters which are clocked to sample the color components at the given multiple of the nominal subcarrier frequency for developing baseband demodulated color signals.

Abstract: A television receiver is disclosed for selectively displaying either a 525 line NTSC video signal or a 625 line European teletext or Viewdata signal. The receiver includes two vertical countdown circuits: a 525 line countdown circuit for use in generating an NTSC type raster, and a 625 line countdown circuit for use in generating a 625 line raster. Switch means are provided for selecting between the two signals generated by the countdown circuits. The receiver CRT uses self-converging, in-line guns.

Abstract: An indirect frequency synthesis, microcomputer-controlled tuning system utilizing a frequency stepping process to tune to a selected channel frequency is disclosed. AFC discriminator information relating to a predetermined frequency range around the correct nominal frequency for the selected channel and the tuning direction toward the nominal frequency is provided to the microcomputer for frequency-stepping the tuner along the AFC discriminator curve in tuning to the selected channel. Vertical sync verification of the detected carrier signal provides more reliable carrier signal detection with the frequency-stepping procedure resumed upon invalid carrier detection. If a limit of the tuning range is reached, tuning is immediately switched to the other limit with the frequency-stepping procedure resumed in the original direction following a predetermined system stabilizing period.

Abstract: An improved baked-hardenable solution and method is disclosed for painting an electrical bridge within a cathode ray tube during its manufacture. The solution is particularly valuable in providing a permanent electrically conductive bridge between the high-voltage charged shadow mask of a color picture tube and the aluminum film deposited on the faceplate to ensure that the aluminum film is charged with the same high voltage present on the shadow mask. The solution according to the invention essentially comprises a mixture of substantially equal parts of glass frit particles and graphite particles each consisting of about 14 to 21 percent weight percent of said solution and in the size range of 0.5 to 10 microns. The particles are in solution in an evaporable solvent consisting of about 14 to 21 weight percent and including a thickening agent in an amount sufficient to provide a paintable viscosity.

Abstract: A loudspeaker protection circuit senses an overload condition caused by an improper input signal or a fault within the amplifier by sensing a DC or infrasonic signal applied to the loudspeaker. The time between zero (axis) crossings of the amplifier output signal, which are related to the lower frequency components of the signal, are detected. If the period of time between zero crossings exceeds a predetermined time limit, the supply of the amplifier output signal to the loudspeaker is interrupted. In order to prevent false tripping of the circuit by normal conditions, the circuit only responds to signals exceeding a predetermined voltage level.

Abstract: An improved low-cost mask-faceplate assembly for a shadow-mask-type color cathode ray tube is disclosed. The assembly comprises a glass faceplate having a dished central section and a rearwardly extending flange. A substantially rectangular, frameless shadow mask has a dished perforate central section and rearwardly extending skirt. The mask is relatively stiff about its major and minor axes, but torsionally flexible and unstable with respect to its diagonals. The mask has an integral rim extending radially outward from the edge of the mask skirt to serve as an electron beam shield and to provide added stiffness for the mask. A corner mask suspension system consists of four suspension devices, one at each corner of the mask. Each device comprises a stud affixed to the faceplate flange and arranged to extend radially inwardly along the diagonal of the faceplate. A leaf spring is provided for detachably inter-connecting the mask corner to the stud.

Abstract: A color demodulation and matrixing system is disclosed for use in a color television receiver. The matrixing portion of the system receives R-Y and B-Y color-difference signals which may be developed by conventional demodulators. Each color-difference signal is converted to a pair of currents of opposing polarities which are coupled to a current node, and a load is coupled to the node for developing a G-Y voltage across the load. The demodulation portion of the system receives the R-Y and B-Y color-difference signals, converts each of them to currents of opposing polarities, and applies them to loads in push-pull fashion to develop R-Y and B-Y output voltages.

Abstract: This disclosure depicts means for providing greater spot size uniformity across the screen of cathode ray picture tubes. A beam-current-control signal is derived from the horizontal scansion circuit means in which the amplitude of the signal varies monotonically as a function of the distance of the beam spot from the minor axis of the faceplate. Means for receiving the beam-current-control signal for modulating the luminance signal are provided. The beam-current-control signal has such characteristics that the modulation causes a predetermined gradational reduction in beam current at least from the minor axis to the minor sides of the faceplate to inhibit beam spot enlargement in faceplate side zones and thus provide greater spot size uniformity across the screen.

Abstract: In a color projection TV system using three cathode ray tubes (one for each of the primary colors green, red and blue), the vertical deflection coils of all three CRT's are capacitively coupled in a series string configuration so that they can be driven by a common amplifier. The capacitors provide AC coupling at the sweep frequency, but maintain DC isolation between the deflection coils. For raster-centering purposes various voltage divider configurations including adjustable resistances are used to establish adjustable DC levels at different ends of each coil. If any of these adjustable resistances are adjusted to apply a potential difference across any of the deflection coils, the result is a constant centering current flowing through each of those coils to maintain steady-state magnetic bias fields for vertical centering of the electron beams. In some configurations the sweep amplifier itself is part of the DC centering current path.

Abstract: Cleansing-scavenging means and method are disclosed for removing detritus from the inner surface of the neck of a cathode ray tube during manufacture. The means comprises probe means for insertion into the neck, and scrubbing means extending from the probe means for dislodging detritus. An expansible and contractible scavenging member is attached to a first end of the probe means. The member has a peripheral surface conformable to the inner surface of the neck for exerting, when expanded, outward scavenging pressure against the inner surface of the neck. Handle means are attached to the second end of the probe means for manipulating the probe means, with associated means providing for expanding and contracting the scavenging member. After the detritus is dislodged from the inner surface of the neck by the scrubbing means, and as the probe means is withdrawn from the neck, the scavenging member when expanded scavenges the detritus from the neck.

Abstract: A chroma amplifier and color killer are described for use in a color television receiver. In a preferred embodiment, the chroma amplifier comprises a first pair of emitter-coupled transistors receiving a current source which has a D.C. operating component and an A.C. chroma signal component. A second pair of emitter-coupled transistors receives another current source which has only a D.C. operating component substantially equal to that received by the first pair of transistors. A variable ACC voltage and a substantially fixed bias voltage are applied to selected base terminals of the transistors such that one of the first pairs of transistors develops a gain controlled A.C. chroma signal output and one of the second pair of transistors develops an ACC-varied D.C. output signal free of chroma component. The latter signal drives a low power color killer for quenching color reproduction when the color component of the broadcast signal is missing or is of very low amplitude.

Abstract: A cathode ray tube socket assembly incorporating controlled, or tuned, spark gaps coupling the high voltage focus grid system to ground to prevent television receiver damage caused by CRT arc-over. Incorporated within the CRT socket assembly are a high voltage spark gap connected to the CRT's G.sub.4 focusing grid and a lower voltage spark gap connected to G.sub.3 focusing grids, each spark gap including ridged sections defining an inter-electrode aperture. By varying the size of the inter-electrode aperture and its distance from each electrode, the spark gap's arc-over threshold voltage and breakdown voltage range from initial arc-over to continuous corona discharge may be precisely controlled.

Abstract: A digital vertical synchronization system for a television receiver has a source of locally generated vertical sync pulses coupled to a vertical sweep system, a source of derived vertical sync pulses developed from and in a time relationship with received television signals, and a phasing circuit for testing the time relationship between the derived vertical sync pulses and the locally generated vertical sync pulses. The phasing circuit outputs a signal indicative of the test. The system includes means responsive to the phasing circuit for adjusting the phase of the locally generated vertical sync pulses, and a mode recognition circuit for determining whether the received television signal includes equalizing pulses in a vertical interval.

Abstract: A system for preventing CRT phosphor burn in a multiple CRT projection type television system is disclosed. The absence of an electron beam deflection signal in the deflection yoke of a CRT is detected and used to provide a signal to CRT shutdown circuitry by means of an unbalanced transformer approach in which the various deflection yoke signals energize a plurality of primary transformer coils with a shutdown signal provided by the transformer secondary when a primary coil flux unbalance occurs.