Main question: What is the purpose of having 4 outputs?
- If I only had pins 1 & 4, I would be able to use 115VAC when it's set to 115VAC, and 240 VAC when it's set to 240VAC.
- For 240VAC setting: pins 2 & 3 are connected together. They seemingly add no functionality. From the diagram, it appears they would just be floating and isolated.
- For 115VAC setting: pin 1,2 and pins 3,4 are connected together. So pins 2&3 just give you an additional pair of 115VAC outputs. Is this the only use?
Background: I'm planning to use the Qualtek 864-10/009 power entry module (http://www.qualtekusa.com/images/EMI_Filters/pdf/86410009.pdf) in a project which will basically just be a fancy box with a 24VDC SMPS and a number of output connectors.
The box may be run on 115VAC or 240VAC, so I chose this power entry module which has a double-fuse with selectable voltage output by changing the orientation of the fuse-holder.
The diagram has some features which I haven't really seen before. After staring at it enough, I think it's clear that it's just indicating which outputs have which voltages depending on the orientation of the fuse-holder (which seems to be represented by the DPDT diagram inside the dashed box).
This raises the question: Why give access to pins 2 & 3? Just to have an additional 115VAC output when the fuse-holder is set to 115VAC? Is it useful for setting up some kind of transformer system (given the similarity of that part of the diagram to a kind of half-transformer)?
Related Post: This other stackexchange post deals with a similar power entry module in the context of transformers, but I couldn't understand their setup or application.
What is the right way to wire a power inlet to a switch to a dual-primary transformer?