Audio detection device null of LSECAM mode terebijiyon

摘要

PURPOSE:To attain excellent sound S/N and sound sensitivity by applying sound detection by means of the pseudo synchronizing detection system to an intermedi ate frequency of a sound carrier frequency-converted by a tuner from the L- SECAM system television signal without further frequency conversion for the detection. CONSTITUTION:No resonance switching voltage is given to a tank circuit reso nance switching terminal 18 in selecting a VHF low band of the L-SECAM system, a switching diode D is nonconductive and the resonance frequency of the tank circuit 17 depends on the resonance capacitor C and the resonance variable coil L, which is adjusted into 40.97MHz. Then the resonance switching voltage is given in selecting other band of the L-SECAM system, the switching diode D is conductive and the resonance frequency of the tank circuit 17 depends on the resonance capacitor C, the resonance variable coil L and the resonance variable capacitor C1 and the coupling capacitor C2 and the frequency is adjusted to 32.4MHz by adjusting the capacitor C1.