PURPOSE: To obtain an easily visible personal computer TV whose operability is good, by providing a means for decreasing automatically only an amplitude of a TV signal, when a personal computer signal and the TV signal is reproduced on a color cathode ray tube at the same time.

CONSTITUTION: When receiving a regular TV broadcast, switches (S)10, 11 are connected to a broken line side in figure, and a TV signal passes through a contrast adjusting circuit 2, and excites a cathode ray tube 4 through a mixing circuit 3. At the time of superimposition, the Ss 10, 11 are connected to a full line infigure, and a personal computer signal also passes through a contrast adjusting circuit 1, enters into the circuit 3 through the S11, mixed with the TV signal and excites the cathode ray tube 4. A contrast of the personal signal and the TV signal is adjusted by a variable resistor 5, 6, respectively. When the S10 is set to the superimposing side, a mid-point voltage of the resistor 6 drops and the contrast of the TV signal is reduced. In this way, an easily visible personal computer TV whose operability is good can be obtained.