Some time ago I asked the group whether the Proto 2000 engines with sound would respond the same to the Broadway Limited device (“Sidekick”) used to active the horn and bell sound on a simple DC track. I received a few answers that thought it might. I finally bought a Proto2000 E6 with sound and it does respond. This makes it easy for me and my 2 year old granddaughter to enjoy the sounds available in the engines from both manufacturers.
Since the Sidekick is made by QSI for QSI sound systems, any brand of locomotive that uses the QSI system whould be compatible with it; i.e., Broadway Limited, Lionel, Proto 2000.
I spoke to a technician who confirmed that the Proto 2000 units with sound don’t have the standard P2K drive. It’s the same or very similar QSI “Quantum” drive used in BLI units.
I plan on buying an undec E8 and paint it in SCL colors.