System Default for frxMgtN393 - used when the
Download Configuration pushbutton on the channel unit
faceplate is pushed and when frxDefaultEnable is set to 1.
When more than frxMgtN392 errors are detected in any
frxMgtN393 monitored Annex-D events, the network is
declared inactive.
This is the Annex-D N393 parameter (Typical value 4)