Rockwell Automation DC3R Isolation Option Board - Manual (Page 14)

8 Installation
Polarity reversal switch connections
To reverse the output voltage polarity without changing the input voltage (or
current) polarity, connect POL REV to COM (terminal 11 to terminal 12). A
single-pole, single-throw switch can be used as a polarity reversal switch
(Figure 6). Close the switch to reverse polarity. Open the switch to return the
output voltage back to its original polarity.
An open collector PNP transistor may also be used to reverse the output voltage
polarity (Figure 7). Another alternative is to use an NPN transistor as shown in
Figure 11 to reverse the output voltage polarity.
IMPORTANT: If using an NPN transistor, additional components must be
installed. Install a 39K ohm resistor in series between Terminal 11 and the
transistor collector, and a 10K ohm resistor between Terminal 6 and the transistor
collector as shown in Figure 8.
Figure 6. Polarity Reversal Switch Connection