KNOW THE LINGO – WHAT IS A RS232?
By: Joseph D. Cornwall, CTS-D, CTS-IAV Technology Evangelist — Legrand
This is one installment in a series of articles in which we'll lift the veils of misunderstanding from the lingo of the AV industry. You can see the rest of our Know the Lingo series in AV University, where you can earn AVIXA CTS certification renewal credits while you learn!
Technical lingo is a kind of shorthand that's used to express concepts common to a specialized area of focus. Technical lingo is important because it provides a precise or unique "shorthand" description of a device, effect or concept. Unfortunately, if you aren't comfortable and familiar with the lingo of a topic it can be a tall hurdle to communicate efficiently with folks who consider the jargon of their field to be "self-explanatory."
What is a RS323?
In 1997, the Telecommunications Industry Association (TIA) issued TIA-232-F, the standard that describes what RS232 is and does in contemporary electronics. RS232 is much older than this, though. The basic outline was first released by the Electronics Industry of America (EIA) in 1962 (!) and was intended to define the communication between an electromechanical typewriter and a data circuit terminating point (called a DCE; an early modem). This was the beginning of teletype!The Electronic Industries Alliance (EIA) was a standards and trade organization for electronics manufacturers in the United States. They developed standards to ensure the equipment of different manufacturers was compatible and interchangeable. The "RS" in RS232 stands for "recommended standard" and was published by the Radio Sector of the EIA.
By the mid 1980's RS232 was a common port used to connect printers and other peripherals to computers. The RS232 serial port, which uses either a DB25 (D-subminiature 25-pin connection) or DB9 connector, operates at voltages from 5 to 15 volts. Because RS232 uses such high voltages its use on computers was replaced with the more efficient USB connection.
RS232 is a serial system and therefore data is sent one bit after another as there is only one data line in each direction. Data on RS232 is normally sent using ASCII (American Standard Code for Information Interchange).
Transmissions using RS232 are limited in speed and link length. Maximum data rates are typically 19,000 baud (19.2 KBd). Compare this speed with USB 2.0 at 480Mbps. RS232 link lengths are limited to about 15 meters, although it can be extended to 100 meters or more when it’s embedded as a payload in an HDBaseT or IP link.
RS232 has become a bona fide industry standard, and it is used in a host of applications that were never conceived when it was first launched in 1962. It is ideal for applications where it is necessary to send data over a straightforward set of cables, as RS232 at its most basic only requires three conductors. RS232 is often used to control displays and projectors, automated screens and masking systems, lighting and heating controls, and various sensors and other devices.
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