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43 Chapter 5
For DTE to DCE connections, use straight-through cable (i.e., you don't
have to reverse lines 2 and 3, lines 4 and 5, and lines 6 and 20 since, in
general, the DCE RS-232 interfaces are reversed themselves).
Therefore, if you are not using CTS, RTS, DSR, DTR and DCD signals,
please short pins 4 and 5 together, and please short pins 6, 8, and 20
together.
Table 5.6: Modem Connections
DB25 Male Modem (DCE)
Pin Signal Pin Signal
2 TxD 2 RxD
3 RxD 3 TxD
4 RTS 4 CTS
5 CTS 5 RTS
6DSR 6 DTR
7 GND 7 GND
20 DTR 20 DSR
8 DCD 8 DCD
Table 5.7: Terminal without Handshake
DB-25 Male Terminal, PC (DTE)
Pin Signal Pin Signal
2 TxD 3 RxD
3RxD 2 TxD
4
5
RTS —
CTS —
7 GND 7 GND
6
20
8
DSR —
DTR —
DCD —