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Installation
2.4.2 External RS485 and RS232 Interface (J1 and J2)
The external interface connectors provide serial remote interface to the switch. An
external controller can connect through J1 (RS-485) or J2 (RS-232C).
Use M&C module switch pack SP1 switch 5 (SP1-5) to configure each switch for
external remote interface type, either RS-485 or RS-232C. The ON position (nearer the
PCB) selects RS-232C interface, and OFF selects RS-485.
The external interface connectors are 9-pin female D connectors with screw locks for
mechanical security. The remote connector is a DCE interface.
Pin Number
2.4.3 Modem Control RS485
The prime and backup modems connect to the switch through J3, the modem control
interface connector. This connector provides the bus-type control interface required for
system operation.
Refer to Sections 4.2.2, 4.2.3, and the remote specifications (Appendixes A and B) for a
complete explanation of the remote interface functions.
Refer to the RS-485 pinout listed in Section 2.4.2
2–6
RS-485
Name
Pin Number
1
GND
2
3
4
+RX/TX
5
RX/TX
6
7
8
+RX/TX
9
-RX/TX
SMS-758 Modem Protection Switch
RS-232C
Name
1
2
RD (RX)
3
TD (TX)
4
5
GND
6
7
8
9
MN/SMS758 Rev. 3
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