Abnormal separation detecting circuits of chromatic signals of SECAM systems

摘要

Abnormal separation detecting circuit of chromatic signals transmitted by a SECAM system comprises a detection circuit which receives a chromatic signal made up of R-Y signals and B-Y signals respectively added with identification signals I1 and I2 at their front ends for detecting the identification signals I1 and I2 to produce currents corresponding to their frequencies, a differential amplifier comprising a pair of transistors ON OFF controlled by pulse signal of opposite signals which vary their phases in synchronism with the initiation of the periods of the R-Y signals and the B-Y signals of the chromatic signal and respectively applied to the base electrodes of the transistors, a current mirror circuit controlled its operation by the differential amplifier circuit, and a capacitor connected across the juncture of the current output terminal of the current mirror circuit and the current input terminal of the differential amplifier, and a reference potential point to be charged and discharged in accordance with the operation of the differential amplifier.