StarTech.com ICUSB422 - Manual (Page 7)

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NOTE: * In “422” mode, the ECHO setting is not used.
The Echo mode is useful for detecting if there is data collision *
occurring on RS-485. If the echoed data is not equal to the
transmitted data, then data collision is occurring.
DB9 Pin Assignment
DB9 Pin RS-422 RS-485
1 TxD - Data +
2 TxD + Data -
3 RxD + NC
4 RxD - NC
5 GND GND
6 NC NC
7 NC NC
8 NC NC
9 NC NC