RS-232: A Short History to the Present

RS-232 serial got its start in the early 1960s as the interface used for connecting Data Terminal Equipment (think electro-mechanical typewriters) and Data Circuit-terminating Equipment (think modems). This type of communication, called the teletype, was a major advance in communications at the time, and in the time before email and fax was the primary method of business-to-business document communication.

As computers became more prevalent, RS-232 became the standard for connecting cathode ray terminals to mainframe computers. This application, starting in the late 1960s, and essential to computing through the 1970s, defined RS-232 as reliable and effective: it put man on the moon.

RS-232 boomed in the 1980s with the advent of the personal computer, and Apple and IBM both made the RS-232 serial port a standard interface on every personal computer for the next twenty years. There were two basic input/output interfaces in use -- RS-232 serial and IEEE 1284 parallel -- and between them users could connect printers, storage devices, mice, personal digital assistants, and virtually every other peripheral in use.

Through this time the serial port also became the standard in the non-consumer market, and makers of cash registers and point-of-sale systems, builders of test equipment, networking hardware manufacturers, building automation designers, medical equipment makers, and hardware users in virtually every other industry adopted the serial port as their primary interface.

For the most part, it is in the non-consumer market where the RS-232 serial port lives today. While many consumers have migrated to USB and wireless technologies for much of their peripheral interfacing in the search for speed and user-friendliness, industrial and equipment makers still find RS-232 the most cost-effective and reliable interface for many applications. It offers easy integration paired with low operating system and processor overhead, concerns that RS-232 addresses well.

Our next article will look more closely at where RS-232 exists in today's world. I think you'll be surprised at how deeply it shapes communications in everyday use.