| 摘要 |
<p>A television signal determination circuit (10) is included in a color circuit. During a burst period, a color signal through a 90 DEG phase-shifter (28) is subjected to frequency-phase conversion to be converted into a phase signal by an APF (14), the phase signal being applied to a phase-comparator (40) in which the phase signal and a color signal from a path (39) are compared with each other. An output of the phase-comparator (40) is applied to an LPF (42), and an output of the LPF (42) becomes a voltage signal having a level according to a phase difference of the both signals. Two voltage signals having different levels are alternately outputted at every 2H in a SECAM system, while only one voltage signal is outputted in other television systems. A rectangular-wave signal is produced from the voltage signal by a sampling/holding circuit (46), the rectangular-wave signal being phase-compared with a rectangular-wave signal delayed by 1H through a 1H delay circuit (48) in a phase-comparator (50). On the basis of a signal according to phase-comparison, and it is possible to determine a television system of the SECAM system or a PAL system. <IMAGE></p> |
