RS232

RS-232 is a standard for serial communication that defines the electrical characteristics and timing for serial binary data transferred between a data terminal equipment (DTE) and a data circuit-terminating equipment (DCE) using single-ended signals. It originated in the 1960s as EIA RS-232 and is often referred to as RS-232-C. The standard has been revised and is commonly known today as EIA/TIA-232-F. RS-232 remains widely used for computer serial ports and peripheral connections, though it has been largely supplanted by USB and Ethernet for new designs.

RS-232 uses unbalanced, single-ended electrical signaling. A logical "1" (mark) is represented by a negative voltage, typically between -3 and -25 volts, while a logical "0" (space) is represented by a positive voltage, typically between +3 and +25 volts. The standard defines voltage levels, tolerances, and timing, along with several connector pinouts. The most common connectors are the 9-pin DE-9 and the 25-pin DB-25; many devices use null modem cables to connect two DTE devices directly. Data transmission is asynchronous, framed by a start bit, data bits (usually 5–8), optional parity, and one or more stop bits.

Practical considerations include distance limits and noise susceptibility of single-ended signaling. Typical ranges are up to about 15 meters at common baud rates, with shorter cables at higher speeds. RS-232 supports hardware handshaking with control lines such as RTS/CTS and DTR/DSR, though not all devices implement them. It played a central role in early personal computers and modems and remains in industrial equipment and embedded systems for simple, robust serial communication. For longer distances or higher data integrity, differential standards such as RS-422 or RS-485 are used.