Additionally，by covering insulated film on the metal electrodes，
the surface-insulated heating core is finished.
The simple-structure heater gives our constant-temperature heat
and does not need any additional temperature applications.
The high insulation-intension heater has many advantage
such as security，giving outheat continuously and keeping steady power ，
being used in a large range of voltage and so on.
PTC heating elements have been widely used for hair permanent clamp，
hair curler, face sauna , heat preservation plate，electric mosquito killer，
