4-8
4.2 Line Interface Units
The Line Interface Unit provides the interface required to connect the internal line modem
(installed in the CPU) to various types of communication lines.
The unit transmitting level is -10 dBm @ 600
Ω
impedance. The receiving dynamic range
is -3 dBm to -47 dBm. The unit’s line impedance is 600
Ω
in both receiving and
transmitting states.
The unit is pre-installed in the horizontal snap at the top of the I/O card cage (above the
CPU and I/O modules).
4.3 Line Interface Options
There are several optional Line Interface Units, each of which supports a different type of
communication. Table
4-4 details the connection type available Line Interface Units:
Table
4-4 Line Interface Unit - Connection Types
Type
Description
Tel Line
(V226)
Interface the internal modem to a telephone line. The telephone
line interface operates in full-duplex mode.
Multi-Drop
(V219)
This option allows the CPU internal line modem to communicate
with several modems in other RTUs, using a single pair of wires.
The multi-drop interface operates in half-duplex mode.
Note that only the 1200 BPS internal line modem is supported by
the multi-drop option
Leased Line
(V404)
This option enables the connection of the CPU internal line
modem to a communication line using a dedicated pair or two
pairs of wires. The leased line interface operates in full-duplex
mode.
RS485
Connection
Board
(V186)
The RS485 Connection Board provides RS485 serial port
expansion from one input port to six expansion ports.
Asynchronous
RS232 Board
(V345)
The Asynchronous RS232 Board connects one of the RTU RS-
232 ports to a computer or terminal.
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