On 16/11/2020 21:11, Dave Liquorice wrote:
On Mon, 16 Nov 2020 19:59:42 +0000, Andy Burns wrote:

It has no means of measuring the voltage

isn't it powered from a wall-wart?

It is.

if that is a straight transformer type with internal regulator, it would
have a scaled-down voltage reference

But judging by it's size and weight its not got much iron in it...

Doesn't need to have. Not to just provide a voltage proportional to the
mains., Lots of turns of very thin wire on the primary of a tiddly iron
transformer will do nicely...

--
A lie can travel halfway around the world while the truth is putting on
its shoes.