Hello Erwin,
With the Esu, the outputs for the track connection are called B and O, with Lenz J and K and with my bidiB the outputs are called 1 and 2
With a 2 rail system one of the wires is called the Ground and the other wire is connected to the rail section to be detected. The Groud is the rail that is not divided into detection pieces.
The attached picture should make it clear.
Kind regards,
Rupert