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)
12
Rec Line (DCD)
23
64
35
J1
(RJ45)
J2
(25-Pin
D-Type)
47
820
58
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
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