I'm trying to implement unipolar symmetric single-channel communication, and I am unable to listen and transmit at the same time (I can only listen to the medium when I'm transmitting a logical 0). I wonder, are there any protocols out there that already implement something of this sort, or does anyone know how I could go about coming up with one? The thing that baffles me is how to initiate a connection. Both devices need to detect each other, and get their clocks in sync, but they cannot detect a collision when both are transmitting a logical 1.