Kay Pirinha,
I believe TVA is a Transformer Volume Control.
When is a Three Letter Acronym not a Three Letter Acronym?
Example: FLA, which is a Four Letter Acronym, a Five Letter Acronym, a Forty Letter Acronym, or a Fifty Letter Acronym.
AMA an Acronym that can be taken as the American Medical Association, or the American Management Association.
NBA refers to both the National Basketball Association and to the National Benevolent Association.
The National Benevolent Association existed decades before the Basketball version.
You can see that I am not a real fan of Acronyms.