For a model railroad project.

I would like to be able to transmit data from a PIC based encoder (with 4x4 Keypad) to a PIC based decoder onboard rolling stock. To turn off led etc.

It will need to be transmitted over a variable 0 to 12 volt dc line. This is similar to the DCC systems now available but I want to do a more simple system for dc.

I dont want to control the dc voltage for locomotive speed.

Thks

Charlie