The 2055 does not have a bell in it, just a motor operated air whistle.
The newer transformers such as your CW-80 have a whistle and bell button to operate the newer trains with electronic sounds. The whistle/bell sounds are triggered by a DC voltage applied to the center rail when the respective button is pushed. One DC polarity will sound the whistle, and the opposite DC polarity will sound the bell on the newer electronic sound locomotives.
The older locomotives such as your 2055 use a relay to activate a motor to blow the whistle/horn. The relay is not DC polarity sensitive like the electronics are, and will pick up with either DC polarity. That is why the whistle blows with both the whistle and bell buttons.
Use the whistle button to blow the whistle on your transformer.
Larry