American Fibertek MT-91P558 - Manual (Page 5)

5
TYPICAL SYSTEM DATA CONNECTIONS
The RS422 or RS485 four wire interconnection between the MT-91P558 and the copper device to
which it is attached is based on industry standard EIA terminology for the transmission of electronic
data signals. Using this terminology, the driver of an electronic signal is labeled TX or Data Out.
Correspondingly, the receiver of an electronic signal is labeled RX or Data In. Following this standard,
the Data Out of the copper device is connected to the Data In of the MT-91P558. The plus terminal of
the copper device is connected to the plus terminal of the MT-91P558 and the minus is connected to
the minus. The reverse flow of data from the MT-91P558 to the copper device follows the same pattern.
Not all manufactures follow standard EIA terminology. Consult the installation instructions for your
copper device if you are unsure which two wires are the drive (data out) wires and which two wires are
the receive (data in) wires.
DATA CONFIGURATION
NOTE: This unit is shipped in the following default configuration.
Channel 1: RS485 (4 wire) or Manchester data
Channel 2: RS485 (4 wire) or Manchester data
Channel 3: Audio
For other configurations, please refer to the drawing below for changes to the default switch settings.
These configuration switches are located on the left side of the unit and can be modified without
opening the unit.
CHANNEL BIAS/TERMINATION SWITCHES
Switches are available internally that allow offset bias and termination features to be activated when
using RS485 data. These switches also allow termination features to be activated when using RS422
data. In order to reconfigure the RS485/422 channel, the module needs to be opened up. To open the
MT-91P558, remove the end panel on the
terminal block side and remove the screw on
the bottom of the module. Slide the PCB
assembly out about half way. The
configuration switch banks are located at the
center of the PCB. The switch bank for
channel 1 is located in line with the BNC
connector. The switch bank for channel 2 is
located in line with the data terminals (See the
drawing on the next page). The chart to the
right describes the layout of each switch bank.