Comtrol DEVICE MASTER RTS - Building Null-Modem Cables (RS-232); Building Null-Modem Cables (RS-422); Building Straight-Through Cables (RS-232;485)

Connecting Serial Devices 15
Building Null-Modem Cables (RS-232)
Building Null-
Modem Cables
(RS-232)
Use the following figure if you need to build an RS-232 null-modem cable. A null-
modem cable is required for connecting DTE devices.
Note: You may want to purchase or build a straight-through cable and purchase a
null-modem adapter.
Building Null-
Modem Cables
(RS-422)
Use the following figure if you need to build an RS-422 null-modem cable. A null-
modem cable is required for connecting DTE devices.
Note: RS-422 pinouts are not standardized. Each peripheral manufacturer uses
different pinouts. Please refer to the documentation for the peripheral to
determine the pinouts for the signals above.
Building Straight-
Through Cables
(RS-232/485)
Use the following figure if you need to build an RS232 or RS-485 straight-through
cable. Straight-through cables are used to connect modems and other DCE
devices.
DeviceMaster RTS
TxD
RxD
RTS
CTS
DSR
GND
DCD
DTR
Signal
RxD
TxD
CTS
RTS
DTR
GND
DCD
DSR
Signal
DB9
2
3
8
7
4
5
1
6
Pins
DB25
3
2
4
7
8
6
Pins
RJ45
4
5
1
8
7
3
6
2
Pins
20
5
Female
RI
N/A
9
22
RI
DB9
3
2
7
8
6
5
1
4
Pins
9
RJ45
5
4
1
3
6
7
Pins
2
8
N/A
DeviceMaster RTS
TxD+
TxD-
RxD+
Signal
RJ45
1
4
8
Pins
Female
DB9
7
3
8
Pins
RxD+
RxD-
Signal
RJ45
Pins
RxD- 2 5
TxD+
TxD-
DeviceMaster RTS
DB9
1
2
3
4
5
8
6
7
Pins
DCD
RxD
TxD or TRx-
DTR
GND
CTS
DSR
RTS or TRx+
Signal
DB9
1
2
3
4
5
8
6
7
Pins
DCD
RxD
TxD or TRx-
DTR
GND
CTS
DSR
RTS or TRx+
Signal
Female
RI 9
9RI
RJ45
6
5
4
2
3
8
7
1
Pins
N/A
RJ45
6
5
4
2
3
8
7
1
Pins
N/A
DB25
8
3
2
20
7
5
6
4
Pins
22