I'm brand new at DCC. I bought a Bachmann Digital Commander deluxe.  When I tried to run my regular DC's on the track with the DCC, the DC engines made a loud electrical sound. They would move but I was concerned about the loud noise.  So I quickly took them off the track immediately.  What's going on?  The instructions said I could run my DC's with the DCC.  I tried to follow the instructions to the Tee. Thanks