Comtech EF Data SMS-758 - Manual (Page 34)

Installation SMS-758 Modem Protection Switch
2–6 MN/SMS758 Rev. 3
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.
RS-485 RS-232C
Pin Number Name Pin Number Name
1 GND 1
2 2 RD (RX)
3 3 TD (TX)
4 +RX/TX 4
5 RX/TX 5 GND
6 6
7 7
8 +RX/TX 8
9 -RX/TX 9
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