NORMAL AND AUXILIARY SYNCHRONIZING PULSE SELECTION CIRCUIT

摘要

PURPOSE:To exclude malfunction due to noise or the like almost completely by receiving a normal frame synchronizing signal and an auxiliary synchronizing signal and selecting and outputting the normal frame synchronizing signal and the auxiliary synchronizing signal alternately in a prescribed timing. CONSTITUTION:A synchronizing frame position signal FD is inputted to a synchronizing signal specifying circuit 3 together with a normal frame synchronizing signal FS and an auxiliary synchronizing signal FH. When the normal frame synchronizing signal is inputted to a set terminal 25 of a control section 25 receiving the normal frame synchronizing signal FS and the auxiliary synchronizing signal FH, a Q output of an output terminal 26 goes to a high level and a Q output of an output terminal 27 goes to a low level. On the other hand, when the auxiliary synchronizing signal is inputted to a reset terminal 28, the processing is opposite to that state above. A synchronizing signal selector 1 uses a 1-bit shift register 15 and 1st-3rd circuits 16-18 to select and decide which of a true normal frame synchronizing signal and a true auxiliary synchronizing signal is to be outputted on each occasion.