DIP Switches
If you remove the battery cover and the battery, you will reveal four DIP Switches mounted on the PCB. These allow you to unlock more features of Earplug 2.

DIP1 (Yellow) Selects the gain of the Mic Amp.
Left = 40db Right = 20db
DIP2 (Red) Selects between 48V Permanent or Switched .
Left = Permanent Right = Switched
DIP3 (Red) Selects between Pink Noise and Tone.
Left = Pink Right = Osc
DIP4 (Yellow) Selects On-Passing of the Mic Amp Signal.
Left = Onpass On Right = Onpass Off