bmoran4 posted:... I'm not sure what traditions the CW and 4090 follow...
The 4090 is the same as the 1033 & 1044 - "U" is the variable tap to the center rail and has the direction & whistle circuitry.
The CW has two versions regarding the common, but both use the red post to center rail for whistle/horn activation with the whistle button. Early versions have the red posts common, later versions(G06 & newer date codes) have the black posts common.