I remember awhile back someone asking what DSP was.  It stands for Digital
Signal Processing.  Originally, the way it used to work was by taking a CW
signal, buried in noise, and record it on the fly on to a computer hard
disk.  Then that audio was filtered of noise before sending it out to the
speaker or headphones.  Now it is all being fed through gigabyte chips.
Anyhow, it attempt to remove the noise and process the CW signal, dumping it
out minus the noise theoretically.  The DSP on my Icom R75 receiver I didn't
consider to be worth while to use.  However, I use it often with the Icom
7000 transceiver.  The other night, I tuned around and found a signal that I
could hear, but not copy, below my line noise.  Turning the DSP on, he came
up out of the noise and although weak, I could copy him perfectly.  Yes, I
use it on SSB signals, too, but it works best with CW signals.

Phil.
K0NX