Build a cable with the following pinout:
RJ 45 connector 9-pin D-SUB
+----+ female male
CTS | 8 |------------------- 8 4
Sig.Gnd. +-+ 7 |------------------- 5 5
DTR | 6 |------------------- 4 8
TxD | 5 |------------------- 3 2
DCD | 4 |------------------- 1 7
RxD | 3 |------------------- 2 3
RTS +-+ 2 |------------------- 7 1
Chass.Gnd. | 1 |-------------------- cover
+----+
RJ 45 connector 25-pin D-SUB
+----+ female male
CTS | 8 |------------------- 5 20
Sig.Gnd. +-+ 7 |------------------- 7 7
DTR | 6 |------------------- 20 5
TxD | 5 |------------------- 2 3
DCD | 4 |------------------- 8 4
RxD | 3 |------------------- 3 2
RTS +-+ 2 |------------------- 4 8
Chass.Gnd. | 1 |------------------- 1 1
+----+
(RJ45 connector view from frontside - cable goes into the paper)
8 CTS Clear to Send
A positive level vorm PAD indicates that
the terminal is allowed to send data.
(only for Hardware-Flow-Control; isn´t
in use in this configuration)
7 Sig.Gnd. Signal Ground
Common signal and DC power supply ground
6 DTR Data Terminal Ready
Used for end-to-end flow control.
positive level from DTE, when it is ready
(not in use in this configuration)
5 TxD Transmit Data (this is the PADs input!!!)
here the PAD receives the transmitted
data from the other source
4 DCD Data Carrier Detect
Posoitive level from PAD whe the local
and remote system are synchronized
3 RxD Receive Data (this is the PADs output!!!)
The other system receives on this pin
the data from the PAD
2 RTS Received by PAD from DTE, controls DCD at
remote side.
1 Chass.Gnd. Protective Chassis Ground
(may be isolated from signal, or connected
to it)
Connect the cable for example to CH2 of the RAD-PAD and on the other hand e.g. to ttyS1 (COM2) of your Linux box.