| 摘要 |
PURPOSE:To reduce disturbance from an address signal to a sound signal by providing the carrier frequency of a sound FM signal at a frequency area between the fundamental harmonic component and the higher harmonic component of the address signal and increasing the level of the sound FM signal in an address signal period. CONSTITUTION:A pair of sound signals are inputted to FM converters 13a and 13b through pre-emphasis circuits 11a and 11b, and adder circuits 12a ad 12b respectively and are outputted as sound FM signals 23a and 23b. The frequency bands of these sound FM signals 23a and 23b are selected so as to be the frequency area between the frequency areas of the fundamental harmonic and of the higher harmonic (mainly tertiary) of the address signal. Noise to the sound signal is reduced because the level of the address signal is relatively low. Furthermore, the signal amplitudes of the sound FM signals 23a and 23b from the third mixing circuit 19 are increased by a gain variable circuit 20 in which the gain of the signals are increased only for the period given from an address period signal generating circuit 10. Therefore, the disturbance from the address signal to the sound signal is reduced to the level not troublesome for an aural sensitivity. |
