I'm looking at this circuit:
Which has come from here
The claim is made that "it detects a voltage drop across a large bridge rectifier that acts as a high power shunt", which is referring to the transformer wired across D1.
However, that transformer appears to be wired in parallel with the rectifier, so wouldn't the coil on the transformer see a full 120V? I don't get how wiring the circuit this way causes the drop over the rectifier to become the supply for the transformer coil. What's going on?
Edit: From the description given, I am under the impression that the coil on the transformer is supplied with a very low (comparatively) voltage. I don't understand why this is the case. The transformer appears to be directly connected to the mains voltage in this circuit - so it should be supplied with 120v.