Terminology and abbreviations

DC 24 V

A value preceded by AC or DC represents a rated voltage containing standard tolerances (normally ±15 %).
Example:
DC 12 V refers to a 12 V battery, regardless of whether it is fully charged (13.7 Vdc) or discharged (10 Vdc).

24 Vdc

A value with the unit (Vdc) at the end is a momentary value that contains no tolerances.

1+1 redundancy

Use of two identical power supply units in parallel in order to ensure continued operation after most failures of a single power supply unit. The two power supply outputs should be isolated from each other by the use of diodes or other switching devices. For example, two 10 A power supply units are required in order to achieve a redundant 10 A system.

N+1 redundancy

Use of three or more identical power supply units in parallel in order to ensure continued operation after most failures of a single power supply unit. All power supply outputs should be isolated from one another by the use of diodes or other switching devices.

Example:
Five 10 A power supply units are required in an N+1 redundant system in order to achieve a 40 A redundant system.