The speed ratio is the ratio of the shaft transmission to the first digit wheel transmission.

速比配置数是出轴与头位字轮传动比。

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While we're on the topic of settings, you can set a maximum and minimum temperature, along with a four-digit password -- you know, so that the kiddies don't have too much fun using that click wheel to crank up the heat.

ENGADGET: iPod fathers unveil their next project, the Nest Learning Thermostat (hands-on)