That's not a "DB"-19. The DB shell is much wider, sized to accommodate up to 25 pins. It's more likely a DA-19, or maybe a DE-19. Or, as the author specified their own dimensions, an unofficial variant.
It is the colloquial term for the connector (regardless of what the 'official' name may be):
> Several computers also used a non-standard 19-pin D-sub connector, sometimes called DB-19,[8] including Macintosh (external floppy drive), Atari ST (external hard drive), and NeXT (Megapixel Display monitor[9] and laser printer).
* https://en.wikipedia.org/wiki/D-subminiature#Common_misnomer...
* https://iec.net/what-is-a-db19-connector/
* https://www.ebay.com/sch/i.html?_nkw=db19+connector
> The early Macintosh and late Apple II computers used a non-standard 19-pin D-sub for connecting external floppy disk drives.
* https://en.wikipedia.org/wiki/D-subminiature#Other
* https://en.wikipedia.org/wiki/File:Mac512k-rear_DB-19_Smartp...
"The DB-19 isn’t really a B shell and probably shouldn’t be called “DB” anything if you’re being precise about naming. Apple called it DB-19 in their documentation, though, and the name stuck."
But ostensibly, everyone who needs to know will know what is meant when a person says "DB9," and thus it works fine.
(Relatedly, the connector used for Ethernet is not an RJ45.)
Wait, what? I cannot find a single source on Google for this - they all say RJ45 is the correct term.
If it's not an RJ45, what is it?
The only thing RJ45 has in common with Ethernet is that it used the same 8P8C-sized connector. But even then, RJ45 had a key notch on the side and Ethernet does not.
[0]: https://en.wikipedia.org/wiki/Registered_jack#RJ45S
For RJ standards, an S suffix signifies that it is a "single line" circuit.
A given jack on a wall in a given office could be wired for a regular single-pair phone, or for Ethernet, or for both -- even at the same time (using the same cabling), as a design intent.
Of course this doesn't work with the gigabit spec we all wound up using, but it was never a popular option to begin with (and nowadays, we usually have VOIP if we even bother with desk phones at all).
However when it came time to specify the pinout when designing ethernet over utp they found the separation required to place the wires like this was too great and degraded the characteristics of the line so they placed a pair on each side keeping the center as is for some sort of compatibility. Like said you could have a phone line in the center of your ethernet. suck to be you it you did that then later wanted to upgrade to gigabit. It also suck if you had some idiot doing the wiring who had the bright idea "herp derp, two pairs of this are not used... I could run two ethernet lines over this cable"
Which is sort of my next complaint, tia-568, the intent was to have the A standard be used with the B standard for compatibility with existing phone lines . Every place I have ever been they just used the B standard. I mean it is not a huge deal, but it always bugged me.
It used to be quite common to see a serial port wired in a B shell, sometimes with just three pins, making a DB-3.
If you were making the point that I shouldn’t care if a bird were a raven or a crow in the background of a painting, sure, that would be pedantry (unless there were some important symbolism). But this is a simple case where a modicum of accuracy can make a big difference.