thanks for your response.  i don't know what the operation was.  the only controls i got with the layout was a control panel for the sidings. i suspect it was not a dcc

recently i started in model trains.  no experience in the "n" scale.  i bought a complete layout that was slightly damaged.  in trying to repair, i found a small circuit that is connected to a "loop".  it appears to have diodes arranged in a full wave rectifier and a dpdt relay plus other components.  two pairs of wires connect track across insulator track connectors.  applying dc to the track causes the relay to click on and off.  if i try to run an engine it sits on the track and changes directions, forward and backward.  what is the circuit for?  help.
97corvette