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The E850483 cable has been discontinued, it has been replaced by the KXUSB cable. Visit this link to purchase the current KXUSB_a Extra Cable - USB RS232 to 3.5MM Cable
The cable supports a computer connection to the product for use with an Elecraft Utility or to enable Logging and Rig Control Programs.
The E8500483 cable plugs into the common USB port on a computer and creates a virtual COM port, when the appropriate drivers are also installed on the computer.