Abstract: Dual-standard (PAL/SECAM) color TV receiver includes circuitry for automatically controlling the receiver's operating mode in accordance with recognition of the SECAM or PAL format of the received signals. A first sample-and-hold circuit monitors the output of an FM detector responsive to the received signals during blanking "backporch" portions of alternate line intervals, while a second sample-and-hold circuit monitors the output of said FM detector during blanking "backporch" portions of the intervening line intervals. Comparison of the outputs of the two sample-and-hold circuits achieves the desired format recognition. To avoid false recognition, sampling interval beginning is delayed relative to beginning of SECAM lead-in oscillations or PAL swinging bursts, while sampling interval termination substantially coincides with end of blanking interval.

Abstract: Dual-mode control signal generator, responding to alternative forms of mode selection signal input by generating different arrays of control signal outputs, includes a trio of voltage comparators. In first form, mode selection signal consists of pulse train with DC component of such a magnitude that all signal excursions remain above a reference potential; in second form, DC component magnitude is such that all signal excursions remain below reference potential. In first comparator, comparison of signal with reference potential switches unvarying control current between output current paths in dependence upon form of control signal. In second comparator, comparison of level shifted signal with reference potential results in a pulse train output, but only in presence of first form of selection signal. In third comparator, comparison of oppositely level shifted signal with reference potential results in development of complementary pulse train outputs in presence of second form of selection signal.