B&R Automation PC 3100 User Manual page 262

Appendix A
A.2 Abbreviations
Abbreviation
NC
ND
NO
TBD
MTBF
262
Stands for
Normally closed
Not connected
Not defined
Normally open
To be defined
Mean time between failures
Table 252: Abbreviations used in this user's manual
Automation PC 3100 User's manual V 1.00 Translation of the original documentation
Description
Stands for a normally closed relay contact.
Used in pinout descriptions if a terminal or pin is not connected on the module
side.
Stands for an undefined value in technical data tables. This may be because the
cable manufacturer has not provided a value for certain technical data.
Stands for a normally open relay contact.
Used in technical data tables if there is currently no value for specific technical
data. The value will be supplied later.
The expected value of the operating time between two consecutive failures.