NTSC scan rates during the switch to color

[Mi40793]

All of the earliest mono broadcast sync generators could be modified to color including the RCA TG-1, circa 1946. RCA sold a option chassis with a 3.58 oven-controlled crystal that counted down and output a substitute 94.5 kHz (31.5 x3 offset from 3.58 rate. 3.58 divided by 455/2 gives 15734 khz) input for the internal TG-1 crystal. A second chassis, connected to the TG-1 generated a burst flag pulse required for the early color camera encoders (along with 3.58 Mhz SC). The 3.58 frequency was held within a few Hz, close enough. Atomic standards for 3.58 are not really necessary except for synchronizing network facilities in the days before frame syncs.