5-3
5.2  RTU to Modem Connection 
5.2.1  RTU-to-Modem Asynchronous Connection 
For a 9-pin or 25-pin connections, use the FLN6458 cable kit to connect one of the 
IRRInet-XL RTU RS-232 ports asynchronously to a modem (The RTU serves as DTE). 
The kit includes a cable with RJ45 modular jacks on both ends and a RJ45 to 9-pin and 
25-pin male D-Type adaptor (See Figure  5-2). 
The possible RTU configurations are detailed in Table  5-1: 
Table  5-1 RTU to Modem Asynchronous Connection 
CPU Port No.  Used with Piggyback 
Board 
Toolbox Definition 
2  -  RS-232 UART External Modem (MDLC) 
3  FRN5724 
RS-232 Asynchronous External Modem, 
Full Duplex or Multi-Drop Half Duplex 
N
N
o
o
t
t
e
e
:
:
 
 
1. Before transmitting, the RTU sends a RTS = on signal to the modem, and will 
not transmit unless it receives a feedback CTS=on signal from the modem. 
2. The RTU will not receive unless it receives a DCD = on signal from the 
modem. 
3. When using a modem in auto-answer mode (connected to a computer port) 
for remote service, the RTU does not support the RTS/CTS protocol, as the port 
is designed to operate with a local computer as well as with a modem. Refer to 
the jumper settings detailed in the Utilities section of the Programming Tool Box 
Operating Instructions manual. 
 
J1
 
(RJ45)
 
J2
 
(25-PIN 
 
D-TYPE
 
Tx_DATA
 
Rx
DAT
 
RTS
 
CTS
 
GND
 
DTR
 
Rec_LINE (DCD)
 
+12V
 
1
 
2
 
6
 
3
 
4
 
8
 
5
 
7
 
3
2
 
(2)3
 
7
4
 
8
5
 
5
7
 
4
20
 
1
8
 
Tx_DATA
 
Rx
DAT
 
RTS
CTS
GND
DTR
 
Rec_LINE (DCD)
 
NOT USED
 
(9-PIN 
 
D-TYPE
RJ45
 
Connector
 
Pin No. 1
 
Pin No. 8
 
 
Figure  5-2 RJ45-to-D-Type Male Connector Adaptor