To transmit a '1', the sender pulls the white line low, the receiver acknowledges this by pulling the red line low. The sender then releases the white line and the receiver finally releases the red line. For transmitting a '0', the sender starts with pulling the red wire low.
This has the nice property that it does bit-level handshaking and flow control and is self-clocking.
Despite these advantages, I've never seen such kind of protocol used anywhere else. If you have, let us know!
scy
Binder
revk
oblomov