Hey Sir J -
..I assume you're asking relative to your ADAT-rip endeavours in the PMs? (I'm guessing, perhaps, you are seeing 'inverted' signals on those 'I' tracks?) If-so, there Was such a thing as 'blanking reverse', which, IIRC, was to accommodate either a Mech-blanked Galvo Amp, or, an 'early Gen DPSS' that required a 'reversed signal' for Intensity.. I think that was common, for example, in Laser Media 'ZAP'-based systems, where that was typically 'reversed'.. IIRC, 'LFI' did it that way, also..
..I'm sure P'fesser Steve / other Elders will correct me where I'm remembering wrong..
Anyhoo, tty in PM..