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Glossary of Technical Terms

COM Retention



The term COM Retention (or COM Port Retention) describes a feature included with some USB Serial Adapters, specifically the ability to maintain COM settings on subsequent installations, even if the original USB port into which the adapter was installed is not used.

Disconnecting most USB to Serial Adapters (that lack this feature) and plugging them into a different USB port on the same computer causes the adapter to be assigned a new COM port number. This can be extremely frustrating and time consuming, since it requires existing software using the serial port to be re-configured each time. With COM retention, the original COM port settings are stored and retained, regardless of the USB port to which the adapter is connected on subsequent use.

If a USB Serial Adapter that does not have this feature is plugged back into the same USB port, there is no issue; however, on  computers with multiple USB ports, this can become a major inconvenience.

After initial installation, USB Serial Adapters that offer the COM Retention feature can be plugged back into any USB port on the same computer, and always keep the same original COM assignment - saving the time and hassle of having to re-configure software.