1.0 link Rainbow Dash Network http://rainbowdash.net/ Techdisk (techdisk) http://rainbowdash.net/techdisk http://rainbowdash.net/notice/3331100 @<span class="vcard"><a href="http://rainbowdash.net/user/2706" class="url" title="a boring guy"><span class="fn nickname mention">mushi</span></a></span> Quite simply, they are a switch controlled by voltage. When used as a switch, it simply turns a circuit on or off depending on if it has voltage on the base pin or not. When used as an amplifier, it can take extremely small volrage waves and use them to control the resistance in a large voltage circuit, therefore amplifying the original small voltage to the new voltage.