As you are aware, many Macintosh computers support the NTSC and PAL video formats and both the Quadra 610 and 650 fall into this category. Their respective sense line configurations to generate the appropriate video signal are listed below.
NTSC Pins 4,7, and 11 (ground) are tied together. Sense pin 10 is not connected (logic high) Pin 5 is the composite signal and pin 6 is composite ground.
PAL Sense pins 4, 7, and 10 are tied together. Pin 5 is the composite signal and pin 6 is composite ground.