Abstract: An interface circuit in a kinescope bias control system includes a transistor with a base electrode coupled to the output of a kinescope drive amplifier in a television receiver, an emitter electrode coupled to a kinescope cathode, and a collector output coupled to an output circuit which provides signals to signal processing circuits. A current related to the kinescope black current level is applied to the emitter electrode. The signal gain from the base electrode to the output circuit is significantly less than the signal gain from the emitter electrode to the output circuit. Spurious signals including noise from the output of the kinescope driver are thereby significantly attenuated at the output circuit, preventing distortion of black current representative signals provided from the output circuit.

Abstract: Dual-standard (PAL/SECAM) color TV receiver includes circuitry for automatically controlling the receiver's operating mode in accordance with recognition of the SECAM or PAL format of the received signals. A first sample-and-hold circuit monitors the output of an FM detector responsive to the received signals during blanking "backporch" portions of alternate line intervals, while a second sample-and-hold circuit monitors the output of said FM detector during blanking "backporch" portions of the intervening line intervals. Comparison of the outputs of the two sample-and-hold circuits achieves the desired format recognition. To avoid false recognition, sampling interval beginning is delayed relative to beginning of SECAM lead-in oscillations or PAL swinging bursts, while sampling interval termination substantially coincides with end of blanking interval.

Abstract: In color TV receiver for SECAM-encoded signals, a single FM detector, subject to line-by-line switching of its center frequency tuning, achieves sequential demodulation of respective SECAM subcarriers. For the purpose of using an identification system of the type shown in U.S. Pat. No. 4,240,102, center frequency tuning at the R-Y subcarrier resting frequency is held throughout R-Y line interval and during lead-in burst of B-Y line interval, terminating at beginning of image portion of B-Y line interval. Transient signal component, associated with switching to B-Y subcarrier resting frequency at beginning of that image portion, is stretched into early segment of image portion by de-emphasis circuit following FM detector.

Abstract: Apparatus is disclosed in a video signal processing system for automatically monitoring and controlling the blanking (black) current level of an image reproducing kinescope. A kinescope cathode output signal proportional to the level of cathode black level current conduction is induced during periodic monitoring intervals during which image signals are absent. The cathode signal is induced in response to a grid drive pulse applied during the monitoring intervals. The induced cathode signal is processed by a digital signal processing network to produce incremental bias control voltage steps for modifying the cathode bias, if necessary, in a direction to produce a desired cathode black current level. In addition, there is disclosed a special form of grid drive pulse which serves to prevent system "hunting" in the vicinity of the correct cathode bias.

Abstract: Color TV receiver subject to reception of SECAM signals incorporates dual-mode identification system for identifying and correcting an incorrect mode of line-by-line switching in SECAM demodulation apparatus. In one (horizontal) mode of operation, identification information is derived from lead-in bursts preceding image signals during active line intervals; in other (vertical) mode of operation, identification information is derived from identification oscillations present during selected line periods within vertical blanking interval. Single FM detector and pair of sample-and-hold circuits responsive to detector output are used in both modes of operation, with mode selection sensitive control signal generators developing detector center frequency tuning control, detector gain control, and sampling control waves of forms dependent on mode selected.

Abstract: In a dual-standard PAL/SECAM color TV receiver, an identification system provides a mode-switching output, permitting automatic switching of the receiver between a PAL-reception mode of operation and a SECAM-reception operating mode, in dependence upon the PAL or SECAM nature of the transmission received. In the SECAM-reception mode, a PAL decoder receives the chrominance component output of a SECAM-PAL transcoder; in the PAL-reception mode, the PAL decoder receives chrominance signals which bypass the transcoder. Luminance signal channel of the dual-standard receiver includes a switchable luminance signal delay line in cascade with a chrominance component trap circuit. Switchable delay line is controlled by mode-switching output of identification system such that delay line is interposed in luminance signal path only during SECAM-reception mode operation.

Abstract: Apparatus is disclosed in a video signal processing system for automatically monitoring and controlling the blanking (black) current level of an image reproducing kinescope having cathode and grid intensity control electrodes. When cathode blanking current is monitored, a reference voltage is applied to the cathode over the entire monitoring interval, and an auxiliary voltage is applied to the grid electrode during a portion of the monitoring interval. A version of the grid voltage appears as an induced cathode output voltage proportional to the level of cathode blanking current conduction. A voltage responsive sensing network coupled to the cathode provides an output voltage proportional to the difference in cathode current conducted over the monitoring interval. This voltage is processed by a sampling network to produce a control voltage for modifying the cathode bias in a direction to produce the desired cathode blanking current level at or in the vicinity of kinescope cut-off.

Abstract: In a SECAM-PAL transcoder, color-difference signals, sequentially recovered from received SECAM signals by a single FM discriminator, are supplied via a first emitter-follower to a first modulating signal input terminal of a balanced modulator, which develops a quasi-PAL signal output using PAL subcarrier frequency oscillations. A DC potential, supplied to a second modulating signal input terminal of the modulator via a second emitter-follower, matches discriminator output level under no-color signal conditions. A third emitter-follower, responsive to a blanking waveform, effects cutoff of the first emitter-follower during blanking periods and delivers elevated blanking pedestal to the first terminal. A fourth emitter-follower, responsive to the same blanking waveform, effects cutoff of the second emitter-follower during blanking periods and delivers matching blanking pedestal to the second terminal.

Abstract: Apparatus is disclosed in a video signal processing system for automatically controlling the blanking (black) current level of an image reproducing kinescope having cathode and grid intensity control electrodes. During measuring intervals when cathode blanking current is to be monitored, a fixed voltage is applied to the cathode over the entire measuring interval, and a locally generated auxiliary signal is applied to the grid electrode during a portion of the measuring interval. A version of the grid signal appears as a cathode output signal proportional to the level of cathode blanking current conduction. A voltage responsive sensing network coupled to the cathode provides an output difference voltage proportional to the difference in cathode current conducted over the measuring interval. This voltage is utilized to modify the cathode bias in a direction to produce the desired cathode blanking current level at or in the vicinity of kinescope cut-off.

Abstract: In a color television receiver including a color image reproducing kinescope with plural cathode electrodes and a common grid electrode, a kinescope driver amplifier arrangement is disclosed for supplying frequency selective video signal drive to the kinescope. The receiver also includes networks for providing wide bandwidth luminance (Y) and plural color (r, g, b) image representative signals containing low and high frequency components, as derived from a composite color television signal. High frequency components (e.g., derived from the luminance signal) above a prescribed frequency are selectively processed in a grid signal path and supplied to the kinescope grid via a grid driver amplifier stage. A high frequency compensation signal derived from the grid signal is combined with each of the plural color signals with a sense to cancel with the high frequency components of the color signals.

Abstract: SECAM subcarrier demodulator employs a multistage limiter-amplifier to supply two inputs to a signal multiplier, one input being supplied directly and the other input being supplied via a phase shifter which imparts a phase shift of 90.degree. at one of the SECAM subcarrier resting frequencies. Positive feedback is associated with the final amplifier stage of the limiter-amplifier to provide said stage with a hysteresis characteristic ensuring development of a limiter output with a rectangular waveshape having rise and fall times of substantial constancy, independent of input signal amplitude variations. Negative DC feedback from the penultimate amplifier stage to the input amplifier stage of the limiter-amplifier assures desired symmetry of limiting action. Color difference signal output is obtained by low pass filtering of the products of multiplication of the respective signal inputs.

Abstract: A wide bandwidth video amplifier suitable for driving a kinescope of a television receiver exhibits suppressed radio frequency (RF) harmonic radiation. The amplifier includes a transistor having a nonlinear conduction characteristic in a region of low current conduction. An input circuit including a source of video signals is coupled to a base electrode of the transistor, and output signals are provided from a collector output circuit of the transistor. Degenerative direct current feedback is provided from the output circuit to the input circuit. Undesired RF harmonics produced by dynamic operation of the transistor in a region of low current conduction is suppressed in a first instance by a nonlinear conduction device (e.g., a forward biased diode) arranged to provide degenerative emitter feedback for the transistor during low current conduction. Harmonic radiation is suppressed in a second instance by a low pass filter interposed between the input circuit and the base electrode of the transistor.

Abstract: A wide bandwidth, low power dissipation, cascode video output amplifier suitable for driving an in-line gun color picture tube or the like. The cascode amplifier includes a low voltage, small signal, common emitter amplifier transistor and a high voltage common base transistor. An active load circuit comprising a transistor of like conductivity with respect to the common base and common emitter transistors is coupled between the collector of the common base stage and a source of operating voltage. A disconnect diode, interposed between the emitter of the load transistor and the collector of the common base transistor, is based to a non-conductive state under quiescent conditions. Voltage dependent current feedback is provided from the emitter of the load transistor to the base of the common emitter transistor. Operating current for the cascode arrangement is provided via a resistor coupled from the operating voltage source to the base of the load transistor and the collector of the common base transistor.

Abstract: A video amplifier suitable for providing amplified image-representative signals to an image reproducing device having a capacitive input impedance component comprises a first wideband amplifier stage which provides video signal voltage gain substantially greater than unity.A second wideband amplifier stage provides approximately unity video signal voltage gain and includes at least one amplifying device having input, output and common terminals. An output load circuit comprising at least first and second resistors is coupled in series relation between the output and common terminals through the power supply. Direct coupling means are provided for supplying amplified video signals from the output terminal to the image reproducing device. Amplified signals are capacitively coupled from the first stage to the input terminal of the second stage.