The RS232 (Recommended Standard 232) interface describes the standard for a serial interface which today is mostly only used as a service or configuration interface. The data rate is strongly dependent on the cable length, but has a maximum of 115.2 kBd.
The transmission is asymmetrical and reacts strongly to common mode interferences. Mostly 9-pin D-Sub variants are used as connectors.
Würth Elektronik Webinar: Signal interface filters - effectiveness under real conditions