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USB to serial UART interface IC FT232RL plus 485e combined which can handle usb and RS485 protocols.
Support 5.5V and 3.3V output if needed, for 3.3V the current maximum is 100mA loading.
Use AWG24 wire UL2464 for this USB RS485 cable.
The electronics function is RS485 transceiver, Tx and Rx, if you need Ground, also can be included.
The output can change to the one fit your equipment with the USB RS485 cable.
Worked with:
http://www.sinetechcable.com/