The current version of the RS-232 was issued in 1997, but its original use was for 1960s telegraphs. Technologically speaking, the RS-232 is borderline artifact, yet it’s still found attached to many PCs in the industrial sector – and for good reason.

You’ll be hard-pressed to find a RS-232 serial port on personal laptop computers in stores today. In recent years, the RS-232 has been replaced with the sleeker Universal Serial Bus (USB). Yet even with its limitations, namely high energy draws, when compared to the newer USB, the RS-232 is still an ideal component for computers within the industrial realm which transfer high volumes of data daily, and whose work environments require a bit more reach power.

RS-232 Basics

The “RS” in RS-232 stands for the “recommended standard” which defines the electrical and mechanical traits of the connector, namely the pin numbering, for example, a 9-pin connector. The port is used to connect a piece of data terminal equipment (DTE), like a computer, to a data circuit terminating equipment (DCE), like a modem.

RS-232 offers flexibility in communicative abilities, in terms of a minimal unidirectional communication, or a more complex bidirectional connection. For a unidirectional communication, the RS-232 requires two wires: the TX/RX and GND. Within a bidirectional configuration, at least three wires are used: TX, RX, and GND. Communication over RS-232 is simple and almost intuitive on the PC’s part, completed with minimal code input and no need for additional software, which USB communication often requires.

As previously mentioned, in recent years, the installation of RS-232 serial ports has been replaced with USB, specifically in personal computer design. Limitations of the RS-232 include slow transmission speeds and large voltage swings, both of which contribute to high energy usage, especially in comparison to the efficient USB. Adding even more appeal, USB also offers a bit more versatility in tasks.

Due to the four wire configuration – ground, 5V, D+ and D – USB goes beyond mere data transfer to offer charging capability. The USB’s versatility, low cost, and sleeker design earned its place in the consumer marketplace. However, even with limitations in the consumer world, plenty of characteristics make the RS-232 a more advantageous element in industrial-use computers than USB.

RS-232 Serial Ports vs USB: When the DTE and DCE Are Not Co-Located

A RS-232 serial port is ideal for situations where the DTE and DCE are farther apart, but ideally no more than 15 meters. USB 2.0 ports only work with up to 5 meters of cable for hi-speed transmissions (480 Mbit/s). This is because if the receiver of the USB waits too long for a reply, it assumes the connection failed.

For the RS-232, any distance more than 15 meters will have maximum capacitance and will require the use of additional cables. If the two terminals requiring connection are within 15 meters, then low-capacitance cables can be utilized, resulting in full speed communication, making the workspace ideal for RS-232.

RS-232 Serial Ports vs USB: When Space Is Vital

USB ports require a protocol for transferring data, adding more required software to facilitate successful transmissions. RS-232 ports don’t need additional software.  In fact, they easily communicate to headless systems, like servers, where no keyboard or mouse commands are inputted.

If your industry is merely interested in data transfer, especially continuous communication and data feed, then RS-232 frees up space for data, rather than for its instructions.

RS-232 Serial Ports vs USB: Older Computers

Since RS-232 serial ports have been around much longer than USB ports, older computers and machinery utilize the uninterruptible connection. Industry-specific consoles or programmable logic controllers often utilize RS-232 simply because that’s the way it’s been, and for the aforementioned reasons, it hasn’t made sense to update the machinery to include USB ports.

Purchasing a new PC with only USB options can prove frustrating if older equipment only features RS-232 ports. While there are RS-232 serial port adaptors available on the market (and ironically connected to USB plug-ins), they won’t work as well as traditional RS-232 serial ports.

Although most personal computers don’t come standard with RS-232 serial ports, industrial computers, which serve far different purposes, find vital use in this older style port. RS-232 serial ports have been criticized for their high-energy usage.  In actuality, however, they are continuously communicating data, which, in some workplaces, is exactly what is required to remain productive. USB offers versatility with data transfer and charging capability, but that comes with additional software and protocol, whereas the RS-232 requires little instruction to operate. Finally, in a work center where machinery is spaced further apart, the RS-232 is the only viable option as the USB only maintains transfer within 5 meters.

Choosing between a RS-232 or USB equipped PC really comes down to knowing what your particular data transfer needs are, then meeting them accordingly with the proper port.