Which standard does the DB-9 connector conform to?

The DB-9 connector conforms to the RS-232 standard, which is a protocol for serial communication. RS-232 defines the electrical characteristics and timing of signals, as well as the physical size and pinout of connectors like the DB-9. This particular connector is commonly used for serial communication and was prevalent in older computer systems and devices for connecting modems and other serial devices.

The DB-9 connector features 9 pins, allowing for a variety of signal and ground connections that facilitate data transmission between devices. The RS-232 standard specifies the voltages used to represent binary signals, which allows for effective communication over short distances, typically up to 50 feet, though this distance can vary depending on the specific application and cable quality.

In contrast, USB connectors are designed for a different type of communication and feature a more complex signaling method. Ethernet connectors, such as RJ45, are used for networking operations following standards for networking protocols, and HDMI connectors are for high-definition video and audio communication, utilizing entirely different technologies and protocols than those laid out in RS-232. Thus, the DB-9's conformity to RS-232 is what distinguishes it from the other options, highlighting its role in serial communication.