For connecting a modem, a computer uses a serial interface defined by the EIA/Telecommunications Industry Association standard RS-232. What do the letters “RS” stand for in RS-232?

Introduction / Context:
RS-232 is one of the most widely known serial communication standards used historically for modems and many peripherals. Understanding its naming clarifies the lineage of serial interface specifications from industry bodies such as EIA/TIA.

Given Data / Assumptions:

• Standard in question: RS-232.
• Context: PC-to-modem serial communication.
• Abbreviation “RS” must be expanded.

Concept / Approach:
“RS” in RS-232 originally stood for “Recommended Standard,” a designation from the Electronic Industries Association before the transition to EIA/TIA naming conventions (e.g., EIA-232). The standard defines electrical characteristics, signaling levels, and connector pinouts for serial interfaces.

Step-by-Step Solution:
Identify the authority: EIA (later EIA/TIA).Recall RS prefix meaning: Recommended Standard.Hence, RS-232 expands to Recommended Standard-232.

Verification / Alternative check:
Later documents often rename RS-232 to EIA-232, but the “RS” expansion remains historically accurate.

Why Other Options Are Wrong:
Recognised standard / Registered source / Regulatory specification: Not the historical expansion used by EIA.

Common Pitfalls:
Assuming RS = “Registered jack” (that applies to RJ-series phone connectors, e.g., RJ-11/RJ-45), not RS-232.

Final Answer:
Recommended standard