Abstract: Generation of digital cursors for serial digital television waveform monitors includes inputting hexadecimal values for the cursors by an operator via a front panel. The hexadecimal values are received by a microprocessor which loads them into appropriate registers of a co-processor. The outputs of the cursor registers in the co-processor are input to respective inputs of a multiplexer together with a digital signal representing a serial digital television signal. A select signal for the multiplexer is generated by a selection circuit that is enabled by a digital cursor ON command when the waveform monitor is in a cursor mode. The selection circuit at predetermined locations of the digital signal generates the select signal so that the appropriate cursor values are inserted into the digital signal at those locations.

Abstract: A bright video line select display for a waveform monitor is achieved by storing a selected line from a video frame of a digital video input signal. The stored selected line is iteratively substituted for a plurality of video lines during the vertical interval of the digital video input signal. When line select mode is selected, those video lines during the vertical interval are displayed as a waveform, resulting in a brighter display of the selected video line.

Abstract: An equivalent time sampler uses an oscillator for sampling an input waveform having a repetitive component. A periodic signal is derived from the input waveform, and an offset frequency is derived from the periodic signal. The periodic signal and offset frequency are input to an offset locked oscillator to generate a sampling frequency that is the combination of the periodic signal and the offset frequency. The sampling frequency is used to obtain a sample of the input waveform for each acquisition cycle of the waveform.

Abstract: An equalized eye pattern instrument inserts an equalizer between the input of the instrument and a display device for the instrument. The equalizer compensates for losses and other distortions in a transmission path so that a digital signal at the input of the instrument may be presented to the display device in a form suitable for eye pattern display. A switch may be used to bypass the equalizer when not needed so that the input digital signal may be directly displayed. Further the equalizer is preferably adaptive so that the input digital signal may be restored to its undistorted form from the source.

Abstract: Error detection for digital television equipment that strips away the vertical and horizontal intervals of a digital video signal so that only the active picture portion of the digital video signal is determined by a digital test signal generated from the digital video signal. The digital test signal has replaced at a predetermined location in the active picture portion of the digital video signal one or more video data words with data values that represent check word data for the active picture portion. The check word data may be inserted into the beginning of one of the horizontal lines of the active picture portion of the next field, or may be modified and inserted into the end of the last line of the active picture portion of the same field of the digital video signal. A receiving instrument processes the output of the digital television instrument under test to generate active picture check word data.

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: 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.