From the power connector.
Pin 1, Pin 2, Pin 3, Pin 4
GND, Tx, Rx, VCC
Red, Black, White, No Connection.
from:
http://www.flickr.com/photos/playerx/734230657/in/photostream/
Masse WS BL
|----_____________ | | | > |____-------------
Masse TX RX from:
http://www.heise.de/mobil/artikel/Datenkabel-selbst-bauen-222729.html