Patent ID: 7027721

Claim:
A variable speed central circuit for use with an electric fan comprising: a fan activation IC; a DC current source having positive and negative power supply terminals; a first resistor; a diode connected in series with said first resistor between said positive and negative power supply terminals of said current source; a first triode having a base and a collector and an emitter; a thermal resistor connected to said diode and said base of said first triode; a second resistor connected between said base and said collector of said first triode; a second triode having a base and a collector and an emitter; a third resistor, said emitter of said first triode being connected to said negative power supply terminal, said collector of said first triode being connected to said third resistor and connected to said base of said second triode; and a fourth resistor connected between said emitter and said collector of said second triode so as to send speed signals to said fan activation IC.