| 摘要 |
PURPOSE:To discriminate assuredly two carrying systems from each other and to simplify the constitution of a channel selection circuit, by dividing the position of a VHF low channel of a band changeover switch into two parts and switching the center frequency of wave detection of a wave detecting circuit or a using IF selecting circuit. CONSTITUTION:Two positions VL1 and VL2 corresponding to a VHF low channel are provided to a band changeover switch 5 connected to the main body 10 of a channel selection circuit. While the signal to be supplied to a decision circuit 7 is extracted from an IF amplification/wave detection circuit 3. Those positions VL1 and VL2 are defined as two positions of CCIR-L and CCIR-B systems of the VHF low channel respectively. An IF selecting circuit 2 selects an IF of the prescribed characteristics to the output of the main body 10. Then the signal selected by the circuit 2 is amplified and wave detected by the circuit 3 and applied to the circuit 7. The received broadcast system is discriminated from the difference between a video career wave and a sound carrier wave which are under wave detection and delivery through the circuit 3. In such a way, the constitution of a channel selection circuit is simplified.
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