Sony STR-DA4400ES Operating Instructions Manual page 9

Indicators on the display
Name Function
A SW
Lights up when subwoofer
is connected and the audio
signal is output from the
SUBWOOFER jack. While
this indicator lights up, the
receiver creates a
subwoofer signal based on
the L.F.E. signal in the disc
being played back or the
low frequency components
of the front channels.
continued
9 GB