What can be defined as a momentary low voltage? 

Answer options:

A. Spike
B. Sag
C. Fault
D. Brownout

B

A sag is a momentary low voltage. A spike is a momentary high voltage. A fault is a momentary power out and a brownout is a prolonged power supply that is below normal voltage. Source: HARRIS, Shon, All-In-One CISSP Certification Exam Guide, McGraw-Hill/Osborne, 2002, chapter 6: Physical security (page 299)