CompTIA Network+ Question A-2

An administrator notices an unused cable behind a cabinet that is terminated with a DB-9 connector. Which of the following protocols was MOST likely used on this cable?

A. RS-232
B. 802.3
C. ATM
D. Token ring

Correct Answer: A

Explanation:
A DB-9 connector is used on serial cables. Serial cables use the RS-232 protocol which defines the functions of the 9 pins in a DB-9 connector. The RS-232 standard was around long before computers. It’s rare to see a new computer nowadays with a serial port but they were commonly used for connecting external analog modems, keyboards and mice to computers.