On electric circuits, with $120$ or $230$ AC mains, there are the wires Live and Neutral. The wiring isn't symmetrical : following the circuit, you cannot switch $L$ and $N$.
However, in Italy, sockets and plugs don't have a specific orientation : it is a matter of how the user push the plug in the socket. You cannot watch the socket or the plug and guess the N and L, there aren't signs. Also internal building to sockets wiring isn't specific.
So, here it is an Italian socket - you are sure only about the middle one :
|*| ? |*| Earth Gnd |*| ?
If the appliance design expects a specific N and L wiring, it is a random 50 % correct / not correct run.
If I recollect well, most of radio appliance show sign N and L wires on their power supply electrical schema.
I spoke with some electrical engineers, they cannot explain me how to match the circuit requirements (and hazard regulations) with the real common practices.
Is the electric schema sufficient to pass the local regulations / certification, even if going in production the appliance is build with a non polarized plug ?