Even though midi cables almost always have five wires inside*, only three are used for standard midi applications.  I have modified my USB midi interface to supply power on those spare wires.  This saves running power to all your midi controllers.  This is especially cool for the WX5. 

This power can be either plugged into the D.C. jack in the side of the Midisport, or supplied by the USB bus itself via a voltage doubling circuit.  (USB power is only 5 volts.)   
*
Modified M-Audio Midisport 2X2
Modified M-Audio Midisport 2X2
Even though midi cables almost always have five wires inside*, only three are used for standard midi applications.  I have modified my USB midi interface to supply power on those spare wires.  This saves running power to all your midi controllers.  This is especially cool for the WX5. 

This power can be either plugged into the D.C. jack in the side of the Midisport, or supplied by the USB bus itself via a voltage doubling circuit.  (USB power is only 5 volts.)   
The D.C. jack is the switching type, and is wired to disconnect the USB power when a wall wart is plugged in.

Hmm... there goes the warranty...
  Ocassionally you come across midi cables that only have three wires inside. The thin ones that you sometimes get for free with midi gear are often like this.