In the olden days, believe it or not, serial communication was one of the main ways of connecting peripherals like joysticks or printers, to PCs. In the wild, pioneering days of IT, the most popular connector type for serial communication was the 9-pin D-Subminiature connector, affectionately named the DB9 or the DE-9.
In the past, nine pins were sufficient to transmit data in series, and although there were drawbacks to DB9 connectors, (which eventually lead them to becoming unfavoured in comparison with USB), the number of devices with DB9 ports or cables on them today is still impressive.
What are the disadvantages of DB9?
Basically, DB9 connectors are pretty big. Consequently, it's difficult to connect and disconnect in confined areas. Also, the pins are exposed in the shell, so they are vulnerable to being bent or damaged. Though the connector can be used without using the thumbscrews, it does not tend to hold as well as other connectors. Of course, if you do use thumbscrews, it becomes time-consuming.On top of this, serial communication tends to be slowish.
Despite these drawbacks, however, the DB9 has not outlived its usefulness. There are actually solutions available for many of the problems mentioned above. For instance, right angle adapters solve the problem of confined spaces by allowing a tight angle without damaging the connector. Widely available D-Subminiature plug and jack covers can protect pins from damage when not mated, and adapters like gender changers and socket savers can reduce the punishment suffered by repeated mating cycles.
What are the advantages of DB9 then?
Yes, DB9 connectors DO have advantages too! In most cases they are much easier to customize, with at least 9 individual pins to carry serial data. Though the speed is slower than other standards, the length of the cable can be much longer. USB, for instance, has a five-meter length limit, but RS-232 (the most common standard for serial data) has no defined length limit, and RS-422 has been used at lengths hundreds of meters long with special equipment.
If your old device only has DB9 connectors on it, never fear! There are lots of options for conversion. You can convert to and from USB, Ethernet, and other standards, allowing you to use your device on any computer today.
If you're looking to find DB9 Connectors: L-com and VPI manufacture products ranging from economical serial cables with many off-the-shelf lengths to high-quality premium cables for demanding applications. Also check out L-com's D-Subminiature adapters for innovative solutions to common problems.
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Although they have been replaced in some applications, D-sub connectors still get the job done and are used in various ways today.