HVAC: Why two wires going to the fan?

Hi,
In my thermostat there is a slot marked "Fan" and there are two wires in that slot. How come? Why would a fan need two signals?
Thanks!
Sam
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Sam Takoy wrote:

Hmmm, TYou did not mention 'stat model/
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The Ghost in The Machine wrote:


http://www.youtube.com/watch?v=VWiVtoRAgCo&NR=1

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One is for when the unit is used in the northern hemisphere, and the other for the southern hemisphere. DO NOT connect both at any time, or there may be an antimatter explosion!
Steve
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Um, maybe there are two fans, or there's something else that needs to come on when the fan comes on?
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