Genlocking to a video signal

Before overlaying color digital computer text or graphics data onto a television signal, a system must encode the graphics data into standard television format. This entails added horizontal and vertical synchronization signals and modulating the color information onto a subcarrier (usually 3.58 or 4.43 MHz). To avoid jagged distortions, the time base of the graphics signals must be locked to the horizontal and vertical sync pulses of the television signal. Similarly, for consistent reproduction of colors, the synthesized color subcarrier for the graphics must be in phase with that of the incoming video signal. Two new Raytheon integrated circuits, the TMC22070 genlocking digitizer and the TMC22190 video encoder, solve these problems cost-effectively.<>