In the book PC 97 Hardware Design Guide, Microsoft deprecated support for the RS - 232 compatible serial port of the original IBM PC design. Today, RS - 232 has mostly been replaced in personal computers by USB for local communications. Advantages compared to RS - 232 are that USB is faster, uses lower voltages, and has connectors that are simpler to connect and use. Disadvantages of USB compared to RS - 232 are that USB is far less immune to electromagnetic interference (EMI) and that maximum cable length is much shorter (15 meters for RS - 232 v.s. 3 - 5 meters for USB depending on USB speed used).
what is the maximum length of a standard rs-232 cable
15 meters