What is RS-232?

R. Kayne

RS-232 (Recommended Standard - 232) is a telecommunications standard for binary serial communications between devices. It supplies the roadmap for the way devices speak to each other using serial ports. The devices are commonly referred to as a DTE (data terminal equipment) and DCE (data communications equipment), and could include items like a computer and modem, respectively.

Serial ports have given way to USB and Firewire ports.
Serial ports have given way to USB and Firewire ports.

Updated designations for this protocol have included EIA-232 (Electronic Industries Alliance) and the more current EIA/TIA-232 (Telecommunications Industry Association). These organizations have voluntarily taken on the protocol and the task of improving it. Though it is sponsored by organizations in the United States, the most current variety is compatible with a standard known as ITU v.24 (International Telecommunication Union). Compliance with the international standard helps manufacturers turn out products that will work in a global marketplace.

Ports for the Recommended Standard 232 (RS-232) cable are still found on many computers.
Ports for the Recommended Standard 232 (RS-232) cable are still found on many computers.

ITU is a United Nations organization and its v.24 (pronounced vee dot twenty-four) communication standards are considered recommendations. In the past, however, the slow nature of the organizations behind international standards sometimes led to varying protocols in the marketplace and the adoption of standards before they were officially "sanctioned." Today, these organizations have streamlined the process of developing and disseminating new standards.

RS-232 sets acceptable voltage and signal levels, along with common pin designations or configurations, for wiring serial connector ports. It also specifies protocols for the control information passed between devices, which includes such events such as indicating the beginning or end of a data stream.

Without standards, manufacturers would have no road map to build compatible product lines for technology. RS-232, or serial ports, are now used almost exclusively for dial-up modems. Other devices that used to use serial ports, like mice, now make use of newer USB and Firewire® ports. As the marketplace gradually switches away from dial-up modems to DSL, cable and satellite, this standard will likely eventually become obsolete.

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Discussion Comments


What is the meaning of '232' in RS-232?


@Mammmood - RS-232 is still a valid standard for personal computers if you need the capability to test specific serial ports. You may have to use an RS-232 adapter depending on your hookups.

Personally, I think USB is far better for all other applications, especially for data transfer. USB is basically a one-size-fits all glove that works with a lot of devices and makes data transfer a breeze.

RS-232 by contrast was not always implemented correctly. Not everyone adhered to the standard so in many cases you needed patch boxes to correct the shortfalls, like correctly applying voltage levels to each pin. You shouldn’t have to be a hacker to use computer equipment. Good riddance to this standard.


RS-232 is not used exclusively for serial modems, although that may be a common application. In the industry I’m in (electrical utilities) we use RS-232 connections to hook up electronic relay tests sets to communications software. It’s a common standard and many test set manufacturers use it, although some have migrated to newer protocols.

We use RS 232 to USB to complete the connections between the test set and the computer running the software.


How many versions of RS are there apart from 232?


so would i be able to stream through this connection?


what does `DB` mean in DB25?


232 is just the numerical assignment to the group of standards concerned with serial protocols. Like wifi standards are IEEE 802.11. Numerical assignments grow out of the way the standards are organized within their respective groups of developers.


What is the meaning of '232' in RS-232?

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