Basic Measurements

Time Code Display

Linear Time Code, also known as Longitudinal Time Code (LTC), is an 80-bit signal with information which makes it possible to accurately identify an individual frame of recorded video. LTC is typically recorded on an unused audio track. The 1740A/1750A-Series monitor provides a voltage- versus-time display of the Time Code waveform, which can be used to check for the following problems:

HNo signal.

HSync word in the wrong position (improper Time Code-to-Video sync).

HLow amplitude or noisy time code signal.

To display the Time Code signal on the monitor, connect the video signal containing LTC to the rear-panel REMOTE connector as follows: pin 12 (+ input), pin 13 (- input), and pin 14 (ground). Push the front-panel TIME CODE button. The display should be a stable square wave.

Sync Word

The trigger point is FIELD 1 of the applied video waveform —either internal or external reference. When synchronized to video, the display is stable. The sync word should appear on the right. If it is missing, drifting, or in another position, there is a problem with the Time Code-to-Video synchronization.

Amplitude

Time code gain is set from the GAIN MENU when TIME CODE display is selected. Gain choices are 0 dBu, 4 dBu, 8 dBu, or 12 dBu. Select gain relative to the system under test. If the waveform monitor display amplitude is much less than would be expected for the given input, a problem may exist with the Time Code level.

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1740A/1750A Series Waveform/Vector Monitor User Manual