DACTs must attempt communication within a certain number of tries. If all attempts fail, the panel must initiate atrouble condition.
NFPA 72 (2022), Section 26.6.4.4.4.2.1:
"A maximum of 10 attempts on one line and 2 attempts on the other line shall be permitted before a trouble signal is indicated." That totals12 attemptsbefore declaring communication failure.

Ground-fault monitoring circuits are required on many fire alarm systems to detect when a wire has unintentionally contacted a grounded surface. During testing, the inspectorintentionally introduces a ground to verify that the panel can detect it.
NFPA 72 (2022), Section 10.17.1:
"Ground-fault conditions shall be annunciated in accordance with the requirements of this Code." Testing method:
Thestandard functional testis tointentionally ground a circuit(typically using a known resistor) and verify the control panel indicates aground-fault supervisory signal.
Correct answer: D. Verify the ground-fault indication when circuits are grounded

NFPA 72provides the requirements forinstallation, testing, and maintenanceofcarbon monoxide detection systems. This includes required signals, testing intervals, and integration with fire alarm control units.
NFPA 72 (2022), Chapter 29 - Single- and Multiple-Station Alarms and Household Fire Alarm Systems:
Also coversCO detection and testing proceduresper Section 29.10.
NFPA 720(the former CO detection standard) was integrated into NFPA 72 in recent editions.
Correct answer: C. NFPA 72

NFPA 72 requires smoke alarms in residential settings to be replaced every10 years, even if they have not shown any signs of failure.
NFPA 72 (2022), Section 29.8.1.4:
"Unless otherwise recommended by the manufacturer, smoke alarms shall be replaced when they fail to respond to operability tests or have been in service for 10 years." Correct answer: C. 10

If you choosenot to send a sample of devices to a lab for testing, thenall nonrestorable, fixed- temperature spot-type heat detectorsmust be replaced after 15 years.
NFPA 72 (2022), Section 14.4.4.4.1:
"After 15 years from the date of installation, all fixed-temperature, nonrestorable heat detectors shall be replaced or tested using a method approved by the manufacturer." If testing isnot performed, thenreplacement of all devices is required.
Correct answer: D. Replace all devices