Pin-outs, Null modem cable, Pc-at serial cable – 3Com 2924-PWR User Manual
Page 221: Null modem cable pc-at serial cable
C
P
IN
-O
UTS
Null Modem Cable
RJ-45 to RS-232 25-pin
PC-AT Serial Cable
RJ-45 to 9-pin
Screen
TxD
RxD
Ground
RTS
CTS
DSR
DCD
DTR
Screen
RxD
TxD
Ground
RTS
DTR
CTS
DSR
DCD
Shell
3
2
5
7
8
6
1
4
1
3
2
7
4
20
5
6
8
Switch 5500
Cable connector: RJ-45 female
PC/Terminal
Cable connector: 25-pin male/female
only required if screen
always required
required for handshake
Screen
DTR
TxD
RxD
CTS
Ground
DSR
RTS
DCD
Screen
DCD
RxD
TxD
DTR
Ground
DSR
RTS
CTS
Shell
4
3
2
8
5
6
7
1
Shell
1
2
3
4
5
6
7
8
Switch 5500
Cable connector: RJ-45 female
PC-AT Serial Port
Cable connector: 9-pin female
only required if screen
Always required
always required
required for handshake
required for handshake
Required for handshake