Plug-In Power

Plug-in (or Bias) Power is a method of providing power to the internal electronics of electret microphones, and is commonly used on consumer equipment. Plug-in Power is only ever provided on 3.5mm mini-jack input sockets as found on domestic sound recorders, 'phones, laptops etc. The format provides a low DC voltage of typically between 3 and 5V, with the positive side of the power supply connected to the unbalanced signal connection(s) in the mini-jack socket. So the tip connection for a mono input, or tip and ring connections for a stereo input. The negative return is via the sleeve connection.