With regard to RS232 usage... As a printer is not DCE (data communications equipment), it should have been wired up as a DTE (data terminal equipment). Before computers became common and affordable, "dumb" VDU terminals and "line" printers were often connected via serial connections (including via private line modems and via PSTN
"dial up" modems).
In theory, only modems and similar communications equipment should be wired as DCE.
The biggest problem with RS232 was that a lot of computer manufacturers did not use 25 way D-connectors and/or did not implement a sensible serial interface. So although there were "standard" crossover cables, they had limited use.
I'm not a network specialist, but each twisted pair in Ethernet cable (10BASE-T
) has different twist ratios per metre. This is done to reduce crosstalk. When twisted pair Ethernet was developed, the primary use was as a star network (see star topology
With both RS232 and Ethernet, as with a lot of electronic interfacing standards, the story is that of evolution. Where previous developments and systems are built upon.
More on the history of Ethernet here Ethernet physical layer