First Alert FA168C-CN User Manual page 18

The OFF key is used to disarm the system, silence alarm and trouble sounds, and
clear alarm memories.
IMPORTANT: If you return and the main burglary sounder is on, DO NOT ENTER, but
CONTACT THE POLICE from a nearby safe location.
If you return after an alarm has occurred and the main sounder has shut itself off, the keypad will
beep rapidly upon your entering, indicating that an alarm has occurred during your
absence.
LEAVE AT ONCE, and CONTACT THE POLICE from a nearby safe location.
+
(Security Code)
The "READY" indicator light will be lit if all zones
are secure, and the keypad will emit a single tone to
confirm that the system is disarmed.
Enter your security code and press the OFF key to silence the alarm (or warning
tones of a Memory of Alarm).
Note the zone in alarm on the keypad display, and make that zone intact (close
door, window, etc.). Now enter the security code plus OFF sequence again to clear
the keypad's Memory of Alarm display.
Simply press the OFF key to silence the alarm. Then enter the security code plus
OFF sequence to clear the keypad's Memory of Alarm display. See the Fire Alarm
System section.
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