JVC 250 - Manual (Page 72)

Chapter 5---Electronics
Model 250 Service Manual 5-17
Figure 5-11 Raster Timing Generator for other PCBs.
Raster Timing Generator PCB - Inputs
V_SYNC - input vertical sync from the Video Processor PCB.
H_SYNC - input horizontal sync from the Video Processor PCB.
G_SYNC - Sync-on-Green sync stripped from green video signal at the Video
Processor PCB.
ISYNC - 5 MHz clock from the System Controller PCB used to generate the
internal sync.