— 40 —
The alarm will reset (clear) when total-mod drops to a
Threshold
Off (%):
value specified by this slider, and remains at or below
that point for the number of seconds set by the
Time Off (Sec):
slider.
In the example shown, total mod must reach 105% and stay at
or above that figure for 15 seconds before an alarm is trig-
gered. Then when total mod drops, it must stay below 105% for
5 seconds for the alarm to reset.
In this case we have determined 105% as a ‘drop-dead’ alarm
figure, with a full 15-second blast of overmod as an alarm con-
dition. This example alarm setting has no hysteresis, but pro-
vision for this has been included as we’ll see next.
‘Hysteresis’
Type Alarms
This discussion relates to a number of alarms, not necessarily
related, but with very similar setup options. This will pertain
to the following:
FM Audio Loss
,
Low Signal
,
HD1 Audio Loss
,
HD
A
Audio Loss
,
HD
B
Audio Loss
and
HD
C
Audio Loss
.
Taking FM Audio Loss
as an example for this
group,
Alarm:
must of
course be set
On
to
function. The grayed-
out
Level (dB):
meter
shows the current pro-
gram audio level for
this channel.
In this case we’re looking for a low-level audio condition, so the
Threshold On (dB):
setting of
–30
is what the program level has to
drop to, and stay below
–30
, for the
Time On (Sec.)
interval of
30
seconds.
For the alarm to reset/clear, program audio must reach and
remain above the
Threshold Off (dB):
figure of
–15
for the
Time Off
period of
5
seconds.
This same logic applies to the other alarms in this ‘hyseresis’
group. Just remember that it’s both level
and
time settings that
will trigger and reset an alarm.
Low Signal Mute
The
Low Signal
alarm has one feature that the others in this
group don’t.
Mute:
may be set
On
to mute program audio when
the alarm is active (triggered and not yet reset/cleared). HD
channels will mute themselves, but FM audio will naturally
‘pitch a hissy-fit’ when the carrier disappears.
RDS Alarms
There are two
Off
or
On
settings for RDS errors. Turning
RDS
Loss: On
delivers an alarm when the RDS subcarrier simply goes
missing. Setting
PI Error: On
gives an alarm when RDS is re-
ceived with a PI code mismatch.
RDS data contains a PI code unique to the station. A PI mis-
match can signal a translator ‘hijacking’ by a radio hooligan, or
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