3. Operation of the Control Panel
Operation of Special System Timers
38
NFS-640 Operations Manual P/N 51334:B 10/03/2003
Operation of Special System Timers
What are System Timers?
There are user-programmable time delays for three specific functions: the Auto Silence Timer, the
Alarm Verification Timer, and the Silence Inhibit Timer. Figure 20 shows a sample System Function
Selection screen with system timer settings. For instructions on changing system functions, refer to the
NFS-640 Programming Manual.
How to View System Timer Selections
You can use the Read Status Entry option (explained in Chapter 4) to view the current selection for the
System Timers. To do so, press the keys shown below in sequence:
The LCD display shows the current selections for System Functions, which includes the three system
timers.
Sample LCD display of a System Function screen with system timer selections:
Figure 20 Sample System Function Selection Screen
How System Timers Work
The control panel can operate with special system timers: Auto Silence Timer, Alarm Verification Timer
and Silence Inhibit Timer.
Auto Silence Timer
A timer that functions like pressing the
SIGNAL
SILENCE
key. When the Auto Silence Timer reaches its
programmed value (600-900 seconds), the control panel automatically shuts off all active outputs
programmed as silenceable. To restart the Auto Silence Timer, press the
DRILL
key.
Alarm Verification Timer
A timer that directs the control panel to ignore a fire alarm for a smoke detector, programmed for Alarm
Verification, while the Alarm Verification Timer is counting. Table 10 contains a summary of how the
Alarm Verification Timer works.
Table 10 Alarm Verification Timer Operation
Continued on the next page...
If
The control panel does this
A second fire alarm occurs while the
Alarm Verification Timer is counting
Ignores the Alarm Verification Timer
The Alarm Verification Timer elapses
and a fire alarm still exists
Activates the fire alarm
The Alarm Verification Timer expires
and a fire alarm no longer exists
Increments the Alarm Verification counter (up to
99) for the device and returns to normal operation
Silence Inhibit Timer set to 180 seconds
Auto Silence Timer set to 600 seconds
Alarm Verification Timer set to 30 seconds
SIL INH=180 AUTO=600 VERIFY=30 USA TIME
TERM=N AC-DLY=Y LocT BLINK=01 ST=4 ACS=N
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