PURPOSE: To eliminate the titled circuit from being affected by external noises, by controlling a line switching circuit in response to a detected output of a burst signal to switch accurately.

CONSTITUTION: A signal leading or delaying a burst signal S5 obtained at burst gate circuit 10 at a 90° phase circuit is given to a switch 33 switchingly controlled in synchronizing with an output signal of a flip-flop 22 for line switching. Burst signals S9 with different phase alternately are outputted from the switch 33. The phase of the burst signals S9 is detected at a reference carrier of B-Y axis. When a DC voltage obtained by smoothing a detected output is a prescribed value or more, since it shows that the line switching is not normal, the flip-flop 22 is controlled to correct the operation.