Abstract: The automatic-discriminating apparatus is constituted by functional blocks such as a killer circuit, an APC circuit, a switch, and an automatic discrimination control circuit. The switch connects one of crystal oscillators to a VCO of the APC circuit by a control signal from the automatic discrimination control circuit. The automatic discrimination control circuit divides one vertical scanning period into predetermined sections. When receiving a killer signal indicating the OFF state from the killer circuit at the predetermined sections even one time, it outputs a control signal holding the connection state thereof to the switch, and holds the APC circuit in the locking state. When receiving a killer signal indicating the ON state at the divided predetermined sections a predetermined number of times, it outputs a control signal connecting the other crystal oscillator through the VCO to the switch.