Uniden SWS 2500NZ Operating Manual page 11

9.
AutoMuteIndicator- A red LED under
M lights to indicate that
you selected the Auto Mute feature.
Note: Every time you turn on the SWS2500NZ, a self-test is performed
for all LEDs and Alert tones. You will hear in-orderfive distinct
tonesfor the X-, K-, and Ka-SuperWideband radar bands as well
asfor SWS and laser. (X Band will not be tested if switched off)
8