Picture in picture Widescreen TV main picture screen display (OSD) circuit is composed of a microprocessor IC003 foot of the feet and IC302 (video signal processing and RGB matrix) and related peripheral components composition. Its feature is that the IC003 does not set up a dedicated blue background signal output port, while the blue character pulse output pin is shared. In the absence of signal state, the microprocessor IC003 pin no radio identification (i.e. synchronous pulse) signal input, a foot high level output signal to eliminate the audio mute audio power amplifier; at the same time the sandcastle pulse generator IC1501 feet (NO SIG), Q1507 output low level cutoff, IC003 foot low level is detected by CPU, and no signal judgment the output pulse to the IC302 blue background, thought the foot IC00 pin output high speed blanking pulse is sent to the IC302 / TV pin OSD Yi switch control terminal, OSD / TV switch in the OSD position, choose blue background chest foot pulse, the drive amplifier output from IC302 pin, tube blue emission electron gun excitation flow? The screen display a pleasing blue grating.