Engineering Documentation

Table Of Contents
Chapter 2 Network Electrical Systems
RS-485 MS/TP Communications
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Fig. 17: Replacing a 2-Wire Node with a 3-Wire Node.
Network Repeater for 3-Wire Networks
When placing nodes on a network repeater, (capable of supporting 3-wire networks),
use the following sample connection methods. An RS-485 repeater that supports 3-
wire interface cabling methods can be purchased from Black Box, (Model ICD107A
along with 12Vdc power source (PSD100). This repeater is fully optically isolated. This
repeater is recommended whenever cable is run between two buildings or sections of
building supplied from separate power sources. Black Box can be found in the Field
Purchasing Guide section 16-05 (http://iknow.us009.siemens.net/fpg/sec16-
05/default.asp).
Network traffic is only allowed to go through two repeaters in series.
Baud rate and mode switches must be setup to conform to network speed and half
duplex 2-wire (vs. 4-wire) operation
The following figures depict several scenarios for network repeater usage.