| 摘要 |
PURPOSE:To prevent occurrence of interference with sound signals caused by the mixture of additional signals into chrominance components, by setting the characteristic of the trap circuit of the recording system of the chrominance components to a value close to the maximum value while the additional signals are superimposed during a vertical blanking period. CONSTITUTION:The output signal of an ACC circuit 4 is supplied to a level detection controlling circuit 13 where the level of the highband component of low-chrominance components overlapping FM sound signals is detected and the detected signal of the circuit 13 is supplied to a trap circuit 5 where the signal is detected and the signal components overlapping the FM sound signals are reduced in accordance with the detected level. The signal of an FM modulator 7 is supplied to a synchronizing separator circuit 14 and separated synchronizing signals are supplied to a killer signal forming circuit 15 where killer signals containing the overlappable period of additional signals are formed. When the killer signals are supplied to the controlling circuit 13, a control signal is formed so that the characteristic of the trap circuit 5 can become value close to the maximum value. Therefore, possibility of occurrence of noise in sound signals can be eliminated. |
