Step 5: Track Skipping
To skip to the next or previous track I am using a switch which rests in its open position (not making a circuit), which is only connected to pins 2, 3 and 4. When pushed to the left it connects pins 1, 2, 3 and 4, and when pushed to the right it connects pins 2, 3, 4 and 5. See Image 1 for clarification.
I have connected pin 3 to the extra earth cable I ran out the back of the stereo jack housing.
Pin 1 has a 220ohm resistor soldered on.
Pin 5 has a 620ohm resistor soldered on.
Both the resistors on pin 1 and 5 are then connected to the function wire coming from the back of the jack housing.
When I push the switch lever left it connects the function wire through the 220ohm resister to earth and the phone knows to skip back. When pushed to the right the function wire connects to the 620ohm resistor and to earth and the phone skips forward.