AUTOMATIC SELECTOR OF BROADCASTING SYSTEM

摘要

PURPOSE: To select a broadcast system automatically by providing a 1st state detection circuit that discriminates a broadcast system of a color burst signal, a 2nd state detection circuit that discriminates a broadcast system from a synchronizing signal, and a 3rd state detection circuit that discriminates the broadcast system depending on an output state of the 1st and 2nd state detection circuit. CONSTITUTION: Upon the receipt of a broadcast signal at an area where the NTSC broadcast system is received, an NTSC signal consisting of a color burst signal and a chrominance signal is received. In this case, when the color burst signal given to a 1st state detection circuit 100 is a signal of the NTSC system, an output of a 1st integration circuit 13 is higher than a reference voltage Vref 1. Thus, upon the receipt of the NTSC system broadcast signal, a high level logic signal is outputted only at an NTSC mode terminal, and a low level logic level signal is outputted to a PAL-M mode terminal and a PAL-N mode terminal. Similarly upon the receipt of the PAL-M, PAL-N broadcast system signals, a high level logic level signal is obtained respectively at the PAL-M mode terminal and the PAL-N mode terminal.