(n.) Short for recommended standard; the Electronics Industries Association (EIA) has established many RS-x standards. Among those standards are the following:

RS-170A is a recommended standard developed by the Electronics Industries Association (EIA) that specifies the parameters of color video signals for the NTSC format used in broadcast and in most consumer video products.

RS-232 is a set of standards that specify three kinds of interfaces: mechanical, electrical, and functional. See figure.

RS-232C is a serial interface standard developed by the Electronics Industries Association (EIA) for use in connecting computers and peripherals. The RS-232C port is a feature on many computing devices, and most equipment with an RS-232C connector can be interfaced, as long as software drivers exist. This standard defines circuit functions and pin assignments. The physical connector comes in the traditional 25-pin version or in the newer 9-pin model. In data communications, this specification defines the interface between data terminal equipment (DTE) and data communications equipment (DCE) using serial binary data. This is the EIA equivalent of ITU-T standard V.24. The RS-232C electrical signal is unbalanced (± 5 volts to ± 12 volts), has polar non-return-to-zero (NRZ), and handles data transfer rates of up to 19.2 kilobits per second (Kbps).

RS-232D is the Electronics Industries Association (EIA) equivalent of ITU-T standard V.28.

RS-422 is the balanced version of RS-232, allowing longer runs and faster transmission. It operates in conjunction with RS-449, which specifies electrical characteristics of balanced circuits and their 37-pin connectors.

RS-422A is a standard developed by the Electronics Industries Association (EIA) that defines the physical and functional features of a computer interface with communications equipment. A balanced line and a 40-pin connector are two of its features.

RS-449 facilitates serial binary data interchange, usually in synchronous transmission modes.

RS-232 interface specifications
RS-449 interface specifications