What Is a RS232 Cable?

The RS232 cable is based on the RS232 standard, developed in the 1960s to allow computers to connect to external devices. While originally intended for modems, the cables began to be used for printers, keyboards and mice. They were made of either a 25-pin or a 9-pin system, where each pin is able to transmit a specific voltage and is used for a specific tasks. The RS232 cables have been largely replaced by USB cables.

Definition

RS232 stands for "recommended standard 232", a traditional method for transferring information between a computer and its peripherals. Instead of using wireless technology or modern cable systems, RS232 uses a serial transmission connector made with up to 25 small pins for plugging into the computer. This cable can only extend about 50 feet under normal circumstances and was used to attach mice or keyboards. In the 1980s, the standard was renamed TIA/EIA-232-E, although the old name is still the most common reference to the standard.

Design

The RS232 is based around a 25 pin system, though some connections may only use part of these pins, such as the 9-pin system. Each pin transmits a negative or positive voltage to form the 1's and 0's of computer data communications. In the traditional RS232 method, each pin also had a specific task.

The first pin acts as the grounding pin to protect the electrical current, the second pin transmits data, the third receives it, the fifth gives a clear-to-send signal and so forth. Cables with the full 25-pin capabilities are used for more complicated tasks where backup, signal quality, and external clock mechanisms need to be supported.

History

The Electronic Industries Association created the RS232 standard in 1962, with several updates versions being released in the subsequent years, most notably version C in 1969. This standardized settings for peripheral equipment on professional computers, and when the time of personal computers came it allowed the manufacturers of printers, keyboards and other devices to create products that would work with all computers. The RS232 was updated in the 1980s and was used for modem connections throughout the early 1990s.

Considerations

The RS232 is one of the few connections still used in computers that supports physical interface, allowing analog signals to be transmitted directly through the pins without any unscrambled or signal reading. This allows technicians to use the standard to directly operate specific machinery with the electrical currents, such as an engineer testing equipment.

Alternatives

The RS232 standard has been largely replaced by other connections, like USB cables. These new cables are faster, more reliable and use less energy than the traditional standard, but they are digital and require the data to be sent in packets and then unpacked.