4 Communication
52
Alpha Technologies
4.7 Installing and Using the External Modem (Continued)
Step 2: Connect and Configure the Modem
Use a shielded, null-modem serial cable, DB–25 male to DB–9 male, to connect the modem
to the CFR.
1
The most common ways to connect the cable are:
•
A null-modem cable with DB–25 male to DB–-9 male ends (Figure 4.20).
•
A null-modem cable with DB–25 male to DB–25 male ends and a 9–25 adapter.
•
A standard straight-through cable with DB–9 male to DB–25 female and a null-
modem adapter.
2
Set the modem’s DIP switches as shown in Figure 4.21.
TIP:
Do not enable auto answer with the DIP switches.
Figure 4.20
External Modem Cable Wiring
1
1
TXD 2
RXD 3
4
GND 5
6
7
8
9
1
2 TXD
3 RXD
4
5
6
7 GND
24
UNIT RS-232
SERIAL CONNECTOR
(9 PIN FEMALE)
MODEM
25 PIN IBM PC
SERIAL PORT
25
Figure 4.21
Modem DIP Switch Settings
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