Tom,
I have the same set of Sharks. I programmed both units with the same engine number so both units have bell and horn sounds. If you set them up using two different engine numbers and run as a train the rear unit will not have bell or horn sounds but will have all the engine sounds. I like hearing the bell and horn from both units, sort of like stereo so I will continue to use the same engine number and run as a engine not a train,
JohnB