at the Cobalt3 PyramidII Fan Silencer.
From the product description, this device basically aids in silencing your
noisy fans when the system does not need it. For example, if you are heavily
using the system, more than likely CPU temperatures will rise which will also
raise case temperatures. This rise in turn causes the sensor on the Pyramid
to kick in and start the process of pumping more juice to the fan. As soon as
case temperatures drop, the sensor sees the change in temperature and starts
limited the amount of voltage, causing whatever fan that's attached to slow
down. This minimizes noise when it is not needed without much human intervention.