Audio Spectrum PM Menu Key Sequence: Measure or (Shift + 4) > Audio Spectrum > Audio Spectrum Audio Spectrum PM Menu Span Press to set the PM audio spectrum span. Use the numeric keypad, the rotary knob, or the arrow keys to set the value. Valid values are 2 kHz, 5 kHz, 10 kHz, and 20 kHz. Scale milli-Rad Press to set the scale in milliradians. Use the numeric keypad, the rotary knob, or the arrow keys to enter a value. Back Press to return to the Measurements menu.