PURPOSE: To attain picture transmission with good quality by providing a discriminating means using a horizontal synchronism or a subcarrier frequency as a reference and a means detecting and discriminating the missing or excess of a horizontal synchronizing signal so as to discriminate the signal based on an OR of both means.
CONSTITUTION: Since the horizontal synchronizing signal 1 is inputted at a prescribed period of interval, a monostable multivibrator circuit MS continues the normal operation. If a pulse marked * in the horizontal synchronizing signal is missing because of some cause, the circuit MS is restored, an OR gate G generates an output signal 2, which informs a fault. Further, an oscillator OSC has a frequency smaller than the frequency of the horizontal synchronizing signal and its output resets always a counter circuit COUNTER. A pulse shown in dotted lines in the horizontal synchronizing signal is inserted because of some cause, the OR gate G generates an output signal 3 to inform the fault.
WADA NOBUYUKI
YAMAUCHI TOSHIYUKI
| JPS57200972U | 1982-12-21 | |||
| JPS5778169U | 1982-05-14 |