Abstract: A method of displaying phase characteristics of a video signal is employed in a system that determines the phase angle between the color synchronization burst signal and horizontal synchronization pulses of a color video signal. The method includes selecting an image location on a display screen of video monitor and forming at the image location an image representing the value of the phase angle. The image is formed with a length along one axis passing through the image location and with a light intensity. One of the length or the light intensity is proportional to the value of the phase angle to provide an indication of the value.

Abstract: A method of sampling a color video signal arranged as a sequence of color frames provides identification of a selected one of the color frames. In a preferred embodiment, the method is directed to sampling a PAL-type color video signal in which each color frame includes multiple video image scan lines that have phase characteristics in one of two polarities. Samples of the color video signal are acquired during preselected first and second successive video image scan lines within one of the color frames in the sequence. The polarities of the samples are then identified to determine whether they correspond to the polarities of analogous video image scan lines during the selected color frame. The selected color frame is identified whenever the polarities of the sampled and the analogous video image scan lines are the same.

Abstract: A method and an electrical circuit determines the phase relationship between the color synchronization burst signal and horizontal synchronization pulses of a single color video signal and the color frame relationship between two color video signals. This is accomplished by regenerating on a line-by-line basis a color subcarrier signal which has a fixed phase relative to the leading edge of a horizontal synchronization pulse. A phase comparison is then made between regenerated color subcarrier signal and the color synchronization burst signal to develop a signal that represents the amount of phase error. The phase error signal is sampled to determine an average phase error for successive lines of the color video signal. Simultaneously, a phase comparison is also made between a 90.degree. phase-displaced version of the color synchronization burst signal and the regenerated color subcarrier signal to provide a quadrature phase error signal.

Abstract: A multistandard vectorscope providing vector displays of two or more composite video standards in a single vectorscope. The present invention utilizes a DC controlled phase shifter and a demodulator that are not frequency sensitive along with a switchable oscillator for switching between multiple video standards.

Abstract: A method and an electrical circuit determines the phase relationship between the color synchronization burst signal and horizontal synchronization pulses of a single color video signal and the color frame relationship between two color video signals. This is accomplished by regenerating on a line-by-line basis a color subcarrier signal which has a fixed phase relative to the leading edge of a horizontal synchronization pulse. A phase comparison is then made between regenerated color subcarrier signal and the color synchronization burst signal to develop a signal that represents the amount of phase error. The phase error signal is sampled to determined an average phase error for successive lines of the color video signal. Simultaneously, a phase comparison is also made between a 90.degree. phase-displaced version of the color synchronization burst signal and the regenerated color subcarrier signal to provide a quadrature phase error signal.

Abstract: Improper operation of a digital data processing apparatus is detected by applying a predetermined pattern of test digits to a data input of the apparatus and determining whether the pattern of digits provided at the data output of the apparatus in response to the application of the predetermined pattern of test digits to the data input is the same as the pattern that would be provided at the data output if the apparatus were operating properly.

Abstract: The suitability of a transmission path (16 or 18) for transmission of digital data is monitored by transmitting a test signal over the transmission path. The test signal is composed of a succession of video signal lines each including a horizontal sync pulse and a pattern of digital 1's and 0's at a predetermined frequency and occurring on each line at the same data positions relative to the horizontal sync pulse. The patterns comprise a reference pattern of alternating 1's and 0's and test pattern of 1's and 0's at random or in a sequence known to be disruptive to the transmission path. The test signal is received and is displayed on a waveform monitor (28) with the reference pattern and the test pattern interleaved with the complement of the reference pattern and complement of the test pattern, so that the four patterns are superimposed and enclose a generally eye-shaped area.