Abstract: A recursive noise reduction filter for video components reduces the noise bandwidth of a signal without degrading the signal spectrum. Demodulated chrominance or peak detected chrominance from a video signal output by a video system in reponse to a video test signal is input to the recursive noise reduction filter which acts as a comb filter to suppress noise significantly at frequencies other than harmonics of the horizontal line rate. The signal is scaled by a first attenuator having a scaling factor of (1-a), where (a) is less than one, and input to a summing circuit. Also input to the summing circuit is a delayed signal from a prior horizontal line scaled by the scaling factor (a). The output of the summing circuit is a filtered output signal. The signal is sampled only during horizontal lines that have the video test signal and is stored for subsequent accumulation with other horizontal lines also having the video test signal.

Abstract: A double display mode for differential gain provides the capability of accurately determining the differential gain of a video system in response to a video test signal without using graticules on a display device. A detected chrominance peak level signal is displayed as a positive and a negative trace on the display device. An offset signal is added to the detected chrominance peak level signal to obtain an overlay on the display device of a first selected point of the traces, and then the offset signal is varied to obtain an overlay on the display device of a second selected point of the traces. The difference in values of the offset signal between the two selected points are used to determine the differential gain of the video system.

Abstract: An XY display transition intensifier increases the intensity of an electron beam of a CRT device when the deflection voltages are changing, indicating a transition between dots on the CRT display. The absolute values of the rate of change of the deflection voltages are determined and summed. The resulting output voltage is applied to the intensity grid of the CRT device to increase the intensity of the electron beam.

Abstract: A periodic output signal is generated at a variable phase relative to a periodic input signal by comparing the input signal with a third periodic signal that has a frequency which is less than the frequency of the input signal and that has a duty cycle which is equal to one-half of the ratio of the frequency of the third periodic signal to the frequency of the input signal. The phase difference is detected between the input signal and a frequency component of the third periodic signal which has the same frequency as the input signal. The output signal is generated at a frequency to maintain a predetermined phase relationship between the periodic input signal and the frequency component of the third periodic signal, and the phase of the output signal relative to the third periodic signal is varied.

Abstract: Apparatus for indicating the timing relationship between a reference point of a repetitive input signal, e.g. the horizontal sync point of a video signal, and a signal element that repeats at a higher frequency than the input signal, e.g. an element of the color burst, comprises a phase-locked oscillator for generating a continuous wave signal that is in phase with the signal element. The continuous wave signal is used to generate a train of pulses having a repetition frequency that is equal to the repetition frequency of the signal element and is selectively variable in phase relative to the continuous wave signal, and this train of pulses is used to modulate a display of the repetitive input signal in a dimension other than one that is used in a normal waveform display, e.g. intensity.

Abstract: A digital phase shifter uses a heterodyne concept to mix a continuous wave (cw) signal with a local oscillator which is an integer multiple of the difference frequency. The difference frequency is phase-locked, and the local oscillator frequency is divided into N increments by a counter. The count of the counter is compared to a microprocessor generated phase shift value which is added to the difference frequency. The phase shifted difference frequency is then converted up to produce the phase shifted continuous wave signal.

Abstract: A visual indication of the relationship between first and second electrical signals, such as the left and right channel signals in a stereophonic audio system, is provided through use of a video vectorscope. The first and second signals are used to modulate the amplitude of two sinusoidal waves at a subcarrier frequency and in phase quadrature, so as to synthesize the chrominance portion of a composite video signal. The two modulated sine waves are additively combined, and the resulting signal is applied to the input terminal of the vectorscope.

Abstract: The present invention relates generally to electrical signal transmission lines which are terminated in a manner enabling efficient use of signal energy transmitted through such lines while preventing signal reflections in such lines, and in particular is directed to a termination circuit for a lossy delay line which includes a pair of emitter coupled transistors having positive feedback to develop a negative impedance to terminate the lossy delay line to compensate for the loss in the lossy delay line.