Installation
22
User’s Manual - SM19202 Fast Poll Modem
Connecting to a Transmission Line
The modem has a transmission line interface that can be configured for 2- or 4-wire analog
connection, where one pair (Tx-A and Tx-B) is used to transmit data and the other pair (Rx-A
and Rx-B) is used to receive data. The transmit pair and receive pair are non-polarized.
Table 2-4 shows the pin numbers and corresponding signals for the modem. Figure 2-6
shows the transmission line interface.
NOTE: For communication to occur, the Rx line of one modem must connect to the Tx
line of the other modem. The modem’s Tx/Rx pair are non-polarized.
NOTE: The modem does not support leased-line operation with DC shielding current.
Leased-line connector pin assignments for the rack-mount module can be
found in the documentation for your Motorola/UDS RM16M.
Table 2-4. Transmission Line Connector Pin Assignments
This Pin Number…
Corresponds to This Signal…
1
Rx (4-wire only)
2
Rx (4-wire only)
3
Tx (Tx/Rx-2-wire)
4
Tx (Tx/Rx-4-wire)
5
Earth Ground (optional)
NOTE: When 2-wire half duplex is used, the TX pair must be used for both transmit
and receive.
Figure 2-6. SM19202FP Modem Transmission Line Interface
