Indeed, but that is essentially (old) 'history'.Older equipment transformers, back in the days when the UK had several voltage standards, would have several adjustable voltage tappings to cope.
Sort-of - except that, in the real world (other than in some very specialised environments) there is not such a thing as a 'set voltage'. Given that there will always be quite a wide range of permissible supply voltages (such as 216.2 - 253V in UK), it makes no sense to design equipment such that it will not work satisfactorily with any voltage within that range.Equipment has to either be designed to work with a range of voltages, or a set voltage.
It can, and often is. Indeed, it could be designed to work over whatever range of voltages one wanted - but the range you mention covers virtually any supply voltage one would find anywhere in the world.Modern SMPSU supplied equipment can be designed to work with anywhere from 100 to 260v.
Yes - but, as above, when they "specify just a single voltage" they obviously don't mean to imply that it will only work at exactly that one voltage.For the avoidance of doubt, I have come across motors with name plates specifying they are able to work on a range of voltages - that ability starts at the design stage. Others specify just a single voltage.
Kind Regards, John
Edit: typo corrected
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