The trick with figuring out the connector is to be methodical. Take the negative lead of the meter and place it in the first contact. Next, use the red lead to measure the voltage on the other two contacts in turn. You will get two readings -- if they are 24 and 32, you are done, and the contact with the black lead is GND. If the voltages are something else, move the black lead to the next contact and repeat the above procedure. You'll only have to do it a maximum of 3 times :-)