"FILTER / OFF" button engages a filter that emulates the frequency response of a microphone placed in front of a 12" speaker
"LIFT / GND" button to help eliminate hum and buzz
"PAD" button engages 15dB pad for reducing hot input levels
"REV / Ø" button reverses the polarity from pin 2 hot to pin 3 hot for correcting non-standard equipment and mis-wired cables or for creating special effects
1/4" input jacks can be used as "INPUT / THRU" or they may be combined with the "COMBINE" pushbutton to safely sum stereo feeds to a single channel