Some electrodes, although few, have a hard-wired cable coming from the electrode that has a male TENS plug that is supposed to plug directly into a regular TENS unit.  If you don’t happen to have a TENS unit, but rather a Zeus or Rimba power box, this clever adapter is all you need to use with either of these boxes provided they have a 2.5mm female socket at the point where you plug your lead wire into the power box.  Some Zeus boxes use a 3.5mm audio jack.  If you look closely at the female end at the bottom of the picture, you will better understand how it works.  You could even plug an ordinary TENS lead wire into this socket if you had a Zeus or Rimba power box and only an ordinary TENS lead available.

If you have a power power box that uses a 3.5mm audio input for its lead wires (Folsom, ErosTek or PES) and want to use this adapter for an electrode as described above, simply also purchase a 3.5mm male to 2.5mm female adapter so the 2.5mm male on this adapter will plug directly into it.  A two-step process, but it will work.