Electronic – How to identify SMD devices from the codes on top of the component

I'm going to post this as an answer as I've seen the same type of question come up multiple times, and for each I've basically commented the same thing:

It's pretty much impossible to identify this sort of component unless you either have a BOM of the circuit, schematic, or already know what they are.

If you have some rough idea of the function they perform and it is something more complex than say a discreet transistor, then you may be able to identify them by searching for parts with that functionality on manufacturer websites and comparing marking codes from datasheets. But really this is a shot in the dark.

Having said that, based on your description, the SOT23 package device is almost certainly some sort of TVS device - used for ESD and Transient (EFT) protection on inputs. These are quite common on RS485 devices as per this TI application note. There are components like this specifically for RS485 in the same package like this one. Doesn't have the same marking code, but will like have the same function.

The other package as pointed out by @jp314 in the comments is likely some kind of line filter. As you have found WE has some in a similar package with similar markings, so this is quite clearly what it is. In fact looking at the datasheets from that link, this part has a marking of 500 and looks identical to your picture.

For both of these parts, it could be inferred from the circuit what the parts do. Finding a datasheet for the exact part is the hard bit.

After googling the code 5393 I stumbled across this datasheet. The component appears to be the Toshiba TA75393F, and for me it matches your schematic perfectly.

It seems like you're using the 7.15V reference to detect the presence of the 380VDC, in fact this reference is hooked to the "-" pin of the comparator, and in the case of the comparator B, once the reference disappears, the output goes to low making the PNP transistor conducting.

On the other side, the comparator A with the positive feedback branch makes me think of a comparator with hysteresis. According to this question it could be an overvoltage detection circuit (and in this case the higher external reference would make sense since you want to trigger your comparator only in the case when the 380VDC source has an overvoltage).