I received a request on running Marklin and HD on the same track. I do this. Each track has a HD controller and a Marklin controller. The Marklin trains will run one way only using the HD controller and will not reverse. The HD trains will not run with the Marklin controllers and could damage the motors.
I have added the types of conversion methods to the page entitled Three Rail Conversions
I would like to use an electric Marklin turntable with my Hornby Dublo 3 rail layout, is this possible?
Many 3 rail layouts use a Marklin electric turntable. The Marklin track is higher than Dublo and you will either have to indent the turntable into the base board, probably the elegant solution or use little ramps to join the Marklin and Dublo track. Good luck