IC5 generates RS-170 NTSC synch. IC1, IC2, and IC3 make up the red, green, and blue video signals that drive the video
encoder section of IC6 to make up the color bars. IC3 is an a 2 counter that drives 4-bit counter IC1. Gates IC2a through IC2b form the R, B, and G, video signals. IC6 encodes these, plus synch, to form an NTSC video output signal, which appears at TP12.