I have added ERR sound to most my dummy engines.
The Blue MP15 is a dummy with sound, light and couplers controlled by a ERR dummy unit.
The Santa Fe dummy engine has sound, lights and coulpers using a ERR dummy unit also.
BNSF #7791 is a MTH dummy engine with sound, lights from ERR.
I have three other dummy engines with sound and lights with ERR dummy boards.
Also a slug unit with a ERR dummy board operating the front coupler and headlight.
The bad news is ERR stopped making the small $25.00 dummy board. But they have a dummy
board that cost more and I don't think it works with the ERR sound board BUT I maybe wrong.