In telecommunications, RS-232 or Recommended Standard 232 is a standard originally introduced in 1960 for serial communication transmission of data. It formally defines signals connecting between a DTE such as a computer terminal or PC, and a DCE, such as a modem. The standard defines the electrical characteristics and timing of signals, the meaning of signals, and the physical size and pinout of connectors. The current version of the standard is TIA-232-F Interface Between Data Terminal Equipment and Data Circuit-Terminating Equipment Employing Serial Binary Data Interchange, issued in 1997. The RS-232 standard had been commonly used in computer serial ports and is still widely used in industrial communication devices.
PCI Express x1 card with one RS-232 port on a nine-pin connector
USRobotics Courier external modem had a DB-25 connector that used the Ring Indicator signal to notify the host computer when the connected telephone line was ringing
Electronic Industries Alliance
The Electronic Industries Alliance was an American standards and trade organization composed as an alliance of trade associations for electronics manufacturers in the United States. They developed standards to ensure the equipment of different manufacturers was compatible and interchangeable. The EIA ceased operations on February 11, 2011, but the former sectors continue to serve the constituencies of EIA.
SCART connector on an RCA Dimensia with EIA text
RMA Resistor Color Code Guide, circa 1945–1950