LN1000 IS Annunciator
21
SECTION 6 ALARM SEQUENCES
Summary
From the sequence tables shown in the following pages, it will be evident that an alarm
occurring causes a flashing visual indication with audible and optional relay drive.
The following pushbutton inputs summarise the user controls
TEST
may be operated at any time and operates on the visual indication and the audible
output, turning on all LED’s, LCD’s and the audible.
These will remain on for as long as the button is pressed.
ACKNOWLEDGE
stops the flashing and audible. If a new alarm occurs on an already
acknowledged system, the horn will sound and the new alarm will flash.
RESET
operates only if the visual is steady and plant conditions have returned to normal.
The relay drive is normally only terminated when the reset operates.
SILENCE
is used only to silence the audible.
First-up sequence
When a group of alarms is initiated, it is often important to know which of them was the first
to occur. This is achieved by both flashing the first-up alarm in a different manner compared
to the subsequent alarms and also showing the 'F' in the LCD display.
Three different first-up sequences are available F1, F2 and F3 as detailed below and in the
following sequence tables.
First-up operation should be used with care with the auto-reset sequence as momentary
alarms can cause ambiguity.
F1
In this mode subsequent alarms appear in the acknowledged state, hence they do not
flash. The audible device does not operate when subsequent alarms occur, unless
still operating from the first alarm. The acknowledge pushbutton will reset the first-up
indication.
F2
In this mode all subsequent alarms do not flash, they will however operate the audible
device. The acknowledge pushbutton will reset the first-up indication.
F3
Additional types of flashing are added so that the first-up alarm can still be identified
when the annunciator has been acknowledged. The acknowledge pushbutton does
not reset the first-up indication this is cleared using the reset pushbutton.
