The AF300 is a Line Isolation Filter which filters out X10
signals and any strong electric clutter ('noise') from the device it is
wired to. It provides attenuation at a 40:1 ratio input to output
respectively, preventing the passage of the X10 signals or 120 kHz
electronic noise from the line side (primary) to the load side
(secondary) and vice versa. The AF300 is used to stop noisy devices from
interfering with the W Home Pro X10 signals, and can also stop X10
signals from entering devices which may inadvertently filter the signal.