Rockwell Automation 1715-OF8I Redundant I/O System User Manual - Manual (Page 282)

282 Rockwell Automation Publication 1715-UM001C-EN-P - March 2014
Appendix C 1715-IB16D Digital Input Module Diagnostics
4.3k  is a close standard value, so we use 3.9 k  which changes the voltage
slightly, but not enough to cause the range to change.
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