SYNCHRONIZING SIGNAL AUTOMATIC SELECTING CIRCUIT

摘要

A circuit which preferentially selects a synchronous signal when a composite image signal and the synchronous signal are simultaneously inputted thereto is disclosed. In the circuit, an image processing circuit(1) receives a color signal. A sync separating circuit(2) separates the color signal into horizontal and vertical sync signals. A horizontal sync detecting circuit(6) outputs a logic signal according to whether a signal is inputted to a horizontal and horizontal/vertical sync input terminal. A first analog switch(sw3) is connected to the horizontal and horizontal/vertical sync input terminal or sync separating circuit(2) according to an output state of horizontal sync detecting circuit(6). A vertical sync circuit(7) separates a vertical sync from horizontal/vertical sync signals. A signal inverting circuit(8) inverts the vertical sync. A vertical sync detecting circuit(9) outputs a logic signal according to whether a signal is inputted to a sync input terminal.