MRC DCC Synchro Sound 750

Item is pre owned in good, operable condition.

Use this speaker by wiring to track power and using your existing DCC- non sound equipped diesel locomotive. Be sure that locomotive is assigned to address “0003”.
Using functions F0-F4 generate sounds such as: Brake squeal, Bell, Short horn, Long horn and Coupler slack. Synchronized sound is matched to the locomotive rpm speed by use of the 28 speed step setting. 

F1) Diesel rumble/bell:
There are only about 4-5 throttle steps to the diesel sound, and using the bell drops the rumble to "idle". Turn it off, and it goes back to the throttle setting sound. You can also use F1 to turn off the background rumble completely. There does not appear to be any "speed table" capability to the internal decoder, which would have allowed tuning the sound response to the throttle steps.
F2) Long air horn sound:
About a 3 second blast.
F3) Short air horn sound:
About 1 second long.
F4) Coupler clank:
The sound of couplers crashing together.
F0) Brake/flange squeal:
A "hidden feature", not listed on the box but in the instructions. Quickly "double clicking" F0 produces this sound.

Be advised that this speaker does not produce steam sounds and there is no volume control. 

The decoder in the unit is a 28 speed step decoder, and must be "status
edited" to work with a 128 speed step system.