One-way vide adapters? What is this?

I have been looking at my local cable store and I came across something that confuses me.
For instance, take this adapter: https://conectica.ro/adaptoare-conve...m-lindy-l38189
It says:
Acest adaptor/convertor face trecerea de la DVI-D (semnal digital) la VGA (semnal analogic).
Functioneaza numai in acest sens, nu si invers! Pentru sens opus: https://conectica.ro/adaptoare-conve...b-lindy-l38184

Which translates to:
This adapter works from DVI-D (digital) to VGA (analog).
It works only in that way, and not the other way around! For VGA to DVI use: https://conectica.ro/adaptoare-conve...b-lindy-l38184

I don't get it, why would it only work one way? And what is one way? I mean in a DVI to VGA adapter, what is the DVI device, the monitor or GPU?

I'm guessing the cables translates the signal from digital to analog, but is unable to process an analog signal and turn it into a digital one
(and thus dvi-d on graphics card, vga monitor)

Quote:

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Originally Posted by Sazzy

I'm guessing ...

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You guess correctly :richter: Most active adapters like this one are one-way. Passive ones should work both ways, if you have the necessary extension cables (but they can't convert a digital signal into an analog one or the other way around).

But the source is always the GPU, correct? In DVI to VGA - DVI is always the GPU?

Basically, yeah. (I'm guessing DVI-D, AFAIK DVI-I can send out both analog and digital, so a passive cable would suffice here)

Though there are cables that also go the other way around, most of them are passive VGA to DVI(-I) ones

Quote:

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Originally Posted by Master Razor

But the source is always the GPU, correct?

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Well, video signals usually originate from there =]