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This is for Jeff: The VIR signal you're talking about was usually generated at the station or mastering house using a Tektronix 1441 VIR signal Deleter/Inserter. The signal could be inserted on line 19 or 20 to give an absolute reference for amplitude and phase characteristics of a color TV program or recording. The signal placed a sample subcarrier burst of 40 IRE at 70% video level followed by a sample unmodulated 50% video pulse on the selected line. The receiver could use these two samples to lock the color reception of the set without worry about transmission distortions which might occur at or near "0" IRE where line burst reference is placed in NTSC. In essence the VIR signal was placed well above sync/subcarrier and the potential distortions which can occur in analog broadcasting.
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