"Martin H. Eastburn" wrote in message
...
They are called 'swinging transformers'

Funny, in the business we always called them tap changers, as did the power
companies that we dealt with (nation wide in the U.S.and parts of Canada).
When dealing with the manufacturers, they called them tap changers too. Glad
you straitened that out. We must have been wrong all these years. I'll have
to let them know.