National Instruments Compact FieldPoint cFP-1808 Quick Start Manual page 13

RS-232 specifies a maximum cabling distance of 50 ft, but improvements in line
drivers and cabling technology often allow you to design your network beyond the
recommendations of the specification.
The RS-232 connector is a 9-pin female D-SUB connector. Figure 1 shows the
pinout.
The cFP-1808 does not use RS-232 hardware handshaking, but it asserts the RTS
and DSR signals for host computers or software that may require these signals. A
host computer that does not use these signals does not need to connect to them.
cFP-1808 Quick Start Guide
5
Legend:
NC = Not Connected
GND = Ground
RX = Recieve
Figure 1. RS-232 Connector Pinout for the cFP-1808
4 3 2 1
9 8 7 6
TX = Transmit
RTS = Request to Send
DSR = Data Set Ready
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