Reference · Codes & Standards
Temporal-Three PatternT-3
The standard evacuation signal: three half-second pulses, a 1.5-second pause, repeated. Required for fire alarm evacuation signals so occupants recognise the same pattern everywhere.
NFPA 72: 18.4.2.1, ANSI/ASA S3.41
Section numbers vary by edition — confirm in the edition your AHJ has adopted.