CT Identification and Specs

I got this current transformer shown below but am confused about how to get It to work, I couldn’t get it’s datasheet.

The part of the label that reads 400A/5A is straightforward - the rated primary current is 400 A, and then the secondary current is 5 A.

But it appears not to be a “proper” current transformer. It appears to need a 12 V d.c. supply on pins 1 & 2, and I’m guessing that pin 4 is the “d.c.” vaIue of the output, which is nominally 5 V, and 400 A primary current gives 2 V peak superimposed on that. My complaint there is it’s mixing rms & peak? - that is meaningless unless the shape of the wave is defined. If it was “2 V rms centred on 5 V d.c.”, or words like that, it would have been clearer.

So quite why the secondary current is even mentioned, I don’t know.

N.B. The domain name is up for sale, that could be why you cannot find any data. I wonder whether there was an attempt to pass off as YHDC (yhdc.com)?