POSITIVE TEMPERATURE COEFFICIENT THERMISTOR DEVICE

PURPOSE:To prevent the residual current from flowing to a degaussing coil and to improve the switching characteristic by connecting the degaussing coil between second and fourth terminals and connecting a power source between first and third terminals to form a degaussing circuit. CONSTITUTION:When power is supplied to a first positive characteristic thermistor 10, a large alternating current flows because the resistance value of the thermistor 10 is first small, and heat is generated by this current. When the temperature reaches the Curie point, the resistance value quickly rises, and the magnetic field magnetized in the peripheral part of a CRT shadow mask is erased. Simultaneously, the current flows to a second positive characteristic thermistor 11 and heat is generated. When the temperature exceeds the Curie point of the second positive characteristic thermistor 12, a bimetal 18 is thermally deformed, and the circuit is opened between the bimetal 18 and a fourth terminal 17 to stop the residual current from flowing to a degaussing coil 21. As the result, color shading in the peripheral part of the CRT shadow mask is completely eliminated.