AC15QTP And AC20QTP Operations Manual....
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It is strongly recommended that an RS-232C optical isolation be included in any RS-232C/SCPI
protocol integration to avoid the creation of ground-loops and ground-fault paths through the
remote communication port; such isolation is not included with the standard product.
6.5.2 RS-485/Modbus
If included in the converter, a Modbus Option converter/optical-isolator will be located adjacent
to the RS-232C serial port (see Figure 5 on page 21).
The Modbus Option included converter/optical-isolator connections are depicted in Figure 9
below.
FIGURE 11: RS-485 CONNECTIONS
