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94 Appendix A Technical specifications
NN46110-316 03.01
The following table provides the X.21 cable pinouts. (The pair suffix A or B refers
to an individual wire within a twisted pair.)
Table 33 X.21 cable pinouts
Standard-
wired end
28-pin male Signal name
Pair number
and conductor
Standard-
wired end
15-pin male Notes
2 TXDA Pair 1A 2
14 TXDB Pair 1B 9
3 RXDA Pair 2A 4
16 RXDB Pair 2B 11
15 TXCA Pair 3A 6
12 TXCB Pair 3B 13
17 RXCA Pair 4A Pair 5A Wires of pair 4 connect to
wires of pair 5, but not to
pins in the DA-15.
9 RXCB Pair 4B Pair 5B Wires of pair 4 connect to
wires of pair 5, but not to
pins in the DA-15.
24 SCTEA Pair 5A Pair 4A Wires of pair 4 connect to
wires of pair 5, but not to
pins in the DA-15.
11 SCTEB Pair 5B Pair 4B Wires of pair 4 connect to
wires of pair 5, but not to
pins in the DA-15.
4 RTSA Pair 6A 3
19 RTSB Pair 6B 10
5 CTSA Pair 7A 5
13 CTSB Pair 7B 12
6 DSRA Pair 8A No conn The term No conn means
the wire does not connect
to a pin in the 15-pin
connector.
22 DSRB Pair 8B No conn The term No conn means
the wire does not connect
to a pin in the 15-pin
connector.