see also: https://allpinouts.org/pinouts/connectors/serial/rs232-eia-232-serial-25-pin/ https://allpinouts.org/pinouts/connectors/serial/rs232-eia-2... There w

see also: https://allpinouts.org/pinouts/connectors/serial/rs232-eia-232-serial-25-pin/ https://allpinouts.org/pinouts/connectors/serial/rs232-eia-2... There were once devices that demanded all the nasty "secondary" lines be implemented.