Appendix A: Cables and Adapters
37
RTU-to-Modem Connections
Only R&TTE approved modems should be used to connect the RTU
to the PSTN.
RTU-to-Modem Asynchronous Connection
For a 9-pin or 25-pin connection, use the FLN6458 cable kit to connect one of the
MOSCAD
-
M RTU RS232 ports asynchronously to a modem. (The RTU serves as DTE.) The
kit includes a cable with RJ45 modular jacks on both ends and an RJ45 to 9-pin and 25-pin
male D-Type adapter (see Figure 21). The possible RTU configurations are detailed below:
Port No. Configurator Definition
1
RS-232 UART External Dialup Modem (MDLC)
1. Before transmitting, the RTU sends an 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.
When the connector is facing upwards, the left-hand pin is Pin No. 1,
and the right-hand pin is Pin No. 8.
Tx DATA
Rx DATA
RTS
CTS
GND
DTR
Tx DATA
Rx DATA
RTS
CTS
GND
DTR
Rec Line (DCD)
1
2
Rec Line (DCD)
2
3
6
4
3
5
J1
(RJ45)
J2
(25-Pin
D-Type)
4
7
8
20
5
8
7
(9-Pin
D-Type)
(3)
(2)
(7)
(8)
(5)
(4)
(1)
+12V
NOT USED
Figure 21
RJ45-to-D-Type Male Connector Adapter
RJ45
Connector
