We have found that USB-RS232 adaptors are not all created equal.
Some clearly work better than others, some are bullet proof, and some prove problematic at the best of times.
Here are some recommendations of units we know to work , and some warnings about units we know to be less successful.
Note that is generally better to have a 2 port adaptor device, (or bigger) , so that both AT Server and AT Editor can be connected over RS232 at the same time
Using a single port adaptor means having to swap cables every time you swap application.
There are occasional issues where, the particular version of Windows (WIN7 especially), and chip-set of the Adaptor can play a part in stability of communication
We have found that the "Prolific" chip sets are the root cause of many problems with USB-RS232 converters in use with AT systems.
This does not mean that they are bad for all applications, just that we have observed issues with the AT hardware and these chipsets.
Specific Model advice.
Known Good adaptors
Trip-Lite Keyspan model USA-19HS
Roline USB2-Rs232 12.02.1048
RedCOM USB-8COM (1 USB-8 RS232 - great for multiple AT's on one server)
BrainBox US-279 (1 USB-8 RS232 - great for multiple AT's on one server)
Known Bad Adaptors
Anything with a Prolific chip-set. This includes...
Note: Win7 is known to be significantly less reliable with USB adaptors than WIn10 / Win 8
If you do find you have problems with another specific model, or great success with another specific model, please do let us know, and we'll add it to this list.