Holtgreven GSE-375 - Manual (Page 15)

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In order to connect network lines in parallel from device to device it is necessary to position two
wires into the same lever socket. This requires that the wire used to build the network be 24 AWG
or smaller to allow both wires to fit into the same lever socket.
Both Half Duplex and Full Duplex
The network boards on both end-points should install jumper 3 on the RS-485 option board to
engage the 120 W termination resistor (R8). The boards between the two end-points should
remove jumper 3 on the RS-485 option board.
The isolated ground (ISO GND) should be connected in parallel from unit to unit. A shielded
twisted two pair cable is recommended throughout the network.
20 M A C URRENT L OOP O PTION
This option will convert the comm port 1 to a 20 mA current loop instead of an RS-232. This is a
digital communication signal and should not be confused with a 4 to 20-mA (or 0-20 mA), which
are analog output signals. The intended use is primarily printers and scoreboard displays.
This option will mount into the socket for the comm port RS-232 chip on the main board. This
option will exclude the use of the RS-485 option board. (I.e. only the RS-485 OR the 20 mA
option can be installed into a Model 370/375).
Installation Instructions
1. DISCONNECT POWER! UNPLUG THE MODEL 370/375 TO INSURE DAMAGE WILL
NOT OCCUR DURING OPTION INSTALLATION.
2. Remove the six 8 mm screws (size) from the bottom plate. Separate the top enclosure
from the bottom plate.