Keyspan USA-19 - Manual (Page 33)

Once the Settings window is open, select USB.
Once USB is selected, turn on or check the Enable USB check box. Below this check box, you
should see an item for your Keyspan USB device. Turn on this check box as well. This will
emulate USB and tells your emulated environment that your Keyspan USB device is connected.
Keyspan:USB Serial Adapter for Mac OS X-v2.x User Manual
This User Manual applies to the Keyspan USB Serial Adapter Software for Mac OS X.
Rev 05jul15 Page 33