Lionel Diesel Horn Battery Eliminator.
The Battery Eliminator is used in place of a C or D size battery that is used to power the horn in your diesel locomotive. No more dead batteries. No leaking battery damage to your locomotive. Install it and never worry about the battery again. 3 Wires for the connection and you are done. No changes are done to the locomotive. Comes with all the parts that are needed to perform the upgrade and installation manual. You need to be able to solder and you must have a working horn and relay assembly.