SIGNAL DETECTOR CIRCUIT

摘要

A circuit for detecting the presence or absence of a television receiving signal is disclosed, wherein a detection output for automatic frequency control is compared with first to fifth levels. A low-level output is produced when the detection output is lower than the fifth level; an intermediate-level output is produced when the detection output is between the fifth and fourth levels; a low-level output is produced when the detection output is between the third and second levels, an intermediate-level output is produced when the detection output is between the second and first levels; and a highlevel output is produced when the detection output is higher than the first level, thus producing an output signal of three-digit level from a single output terminal.