Specifications

32 RS-422/485 Application Note
 Copyright B&B Electronics -- Revised October 1997
B&B Electronics -- PO Box 1040 -- Ottawa, IL 61350
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Table 4.1 Comparison of Protection Techniques
Optical Isolation Shunting
Requires no ground reference Must have low impedance ground path
Adds no loading to data lines Presents additional capacitive loading to data
lines
Higher complexity Lower complexity, uses passive components
Effective on common mode
transients
Effective on both common and differential
mode transients
Not dependent on installation
quality
Can be improperly installed by user
Requires an external power source No power required
Not affected by long term or
continuous transients
Subject to damage by long duration
transients