DEVICE FOR RESTRAINING ELECTRIC FIELD RADIATION FROM CATHODE-RAY TUBE

摘要

PURPOSE:To reduce electric field radiation from the front face of a cathode-ray tube in order to solve the problem of electric field radiation in a VDT adversely affecting human bodies. CONSTITUTION:A demagnetizing coil 3 disposed near the peripheral portion of the front face 2 of a cathode-ray tube 1 is used effectively in order to apply to the demagnetizing coil 3 a voltage whose porality is reversed with respect to an electric field 12 radiated from the front face 2 of the cathode-ray tube 1. The voltage of the reversed polarity is given by the phase reversing of an output signal 18 and/or an anode voltage fluctuating in vertical synchronization, the output signal 18 being obtained by a fly back transformer 17 from the output signal 16 of a horizontal deflection circuit 15. A demagnetizing power supply 4 generating ac demagnetizing currents to be given to the demagnetizing coil 3 is completely disconnected from the demagnetizing coil 3 by opening of relay contacts 7,8 according to a timer-controlled relay switch 9 after the demagnetizing action of the demagnetizing power supply 4.