| 摘要 |
PURPOSE:To reduce an adjacent disturbance in a sound FM multiplex system sufficiently for its practical use, by prescribing a compression and expansion ratio of amplitude of a sound signal to be recorded, to an optimum value, in accordance with a level ratio of a desired FM sound signal and a disturbance FM sound signal. CONSTITUTION:A sound signal inputted from a terminal 1 passes through a preemphasizing circuit 2, and after that, is inputted to a 2/3 compressing circuit 6 through a switch 3 in case of an SP mode, and on the other hand, is inputted to a 1/2 compressing circuit 4 through a switch 5 in case of an LP mode. Subsequently, an output signal of the circuit 6 or 4 is FM-modulated 9 through a switch 8. Its output is added to an input video signal and is azimuth-recorded on a magnetic tape 12 by a magnetic head 11. Subsequently, a reproduced signal is FM-demodulated 14 through a BPF13, and as for its output, a noise caused by switching the head is processed by prevalue-holding by a holding circuit 16. After that, as for an output signal of the circuit 16, its dynamic range is restored by a 3/2 time expanding circuit 18 and a twice expanding circuit 20, in case of an SP mode and an LP mode, respectively. |
