| 摘要 |
PURPOSE:To prevent the production of abnormal sound, by avoiding the error in the number of horizontal synchronizing signals, through the decision of expansion and contraction of composite synchronizing signals due to mixture of noise and the fields of odd/even numbers and the control according to the result of decision. CONSTITUTION:To the input of a polarity inversion circuit 28 forming an expansion and contraction deciding circuit J, an output signal 22a from a switching control signal generating circuit which shows if the input is in compensated state, is given. Decision pulses for expansion and contraction are respectively given to the output of AND circuits 24, 25. Thus, the expansion and contraction of composite synchronizing signals can be decided. Next, it is decided as an even number of field if a pulse 7b for decision is presented in a pattern V synchronizing signal 3a of H/2 pulse width and the 7b is presented in a signal delaying the pattern V synchronizing signal 3a by H/2. The control mode changes from the result of decision, allowing to avoid the production of abnormal sound through avoiding the number of horizontal synchronizing signals in error. |
