How are toy train smoke unit and whistle/bell/horn powered?

[FJ and G]

As some of you know, I'm using DC batteries and R/C gear to power my AC toy trains. I'm thinking that no special requirements are needed for the smoke unit, as that could be powered from the same DC battery that connects to the motor(s).

However, it is my understanding that the bell, whistle, horn are powered by a special pulse or waveform that's shaped differently than normal so that it is recognized as distinct from track power. As such, that would be more challenging.

[lionelsoni]

Traditional air whistles are powered from the track voltage, using a motor very similar to the locomotive motor.  Traditional Diesel horns are powered by 1.5 volts DC, from the D cell carried in the locomotive.  Both of these are controlled by the whistle relay, which is sensitive to a small DC component superimposed on the track voltage.

Of course, you wouldn't need a whistle relay.  You can run the whistle motor directly from AC or DC, in the 12-volt ballpark.  The horn is a little harder.  You can buy the same kind of buzzer to run on 12 volts or thereabouts.  Or you can use an ordinary relay to switch the horn onto the D cell.  Or you can reduce the voltage from your RC receiver to 1.5 volts.

It's hard to give a definite answer for modern noisemakers without knowing the design details.  But I would bet that, if you simply powered them from a channel of the sort of controllable DC voltage that you are using for the locomotive motors, they would work, with the polarity selecting whistle-horn versus bell.