Pin RS232 Pinout Explained

[ryan-duve]

https://stratusengineering.com/rs232-9-pin-pinout/

[h2odragon]

see also: https://allpinouts.org/pinouts/connectors/serial/rs232-eia-2...

There were once devices that demanded all the nasty "secondary" lines be implemented.

[jaclaz]

Truism of the week:

>An RS232 pinout 9 pin cable features nine pins

[h2odragon → jaclaz]

But often not 9 actual cables; it was very common to find 8 wire cables that left RI floating.

[jaclaz → h2odragon]

Sure, just like the 25 pin connector in PC's was used with less than 25 wires cables, leaving most of the pins unconnected:

https://allpinouts.org/pinouts/connectors/serial/pc-serial-2...

still a 25 pin connector has twentyfive pins and a 9 pin one has nine pins.

The same (DB25 or DB9) connector has been in use in countless devices with even less wires, null-modem cables had only 7:

https://www.firewall.cx/networking-topics/cabling-utp-fibre/...

And if the cable/connection was monodirectional, even less, I seem to remember repairing a connector of a cable going to a serial printer having only 4 wires (or were they 5?) on a DB25 connector.