— 16 —
Panel Lockout
When the
PANEL LOCKOUT
terminal is grounded,
all
front-
panel buttons are disabled. Web-interface control remains ac-
tive, however.
Alarm Tallies
The four alarm lines are open-collector NPN transistors that
saturate to ground with an alarm.
LOW SIGNAL
,
MULTIPATH
and
AUDIO LOSS
conditions, as well as remote indication of the
PEAK FLASHER
, all have corresponding rear-panel terminals to
enable remote display.
These tally outputs can sink 50mA from an external power
supply without stress. The +5 volts provided on the two right-
hand terminals is current-limited, however, and is intended for
LEDs, optical couplers or other low-consumption devices.
Figure 6, below, suggests a possible remote hookup, which in-
cludes a carrier-loss indication that would be difficult to ignore.
Figure 6 –
Suggested Remote Alarm Connection
DE-EMPHASIS SELECTION
The 531N accommodates both the 75-microsecond (Western
Hemisphere) and 50-microsecond (Europe and Asia) FM broad-
casting pre-emphasis standards. De-emphasis that is appropri-
ate to the shipping destination is set at the factory, but this is
easily changed if required.
Changing
De-Emphasis
Remove the top cover of the 531N. With the front panel facing
you, locate the long row of integrated circuits just behind the
rear-panel
AM NOISE
connector. On either side of IC35, you’ll
find 3-pin jumper strips, each with a removable jumper shunt.
The jumpers are labeled JP3 and JP4. Each is marked with a 50
and a 75, corresponding to the de-emphasis selection. Figure 7
on the following page shows proper placement of the jumper
shunts for each characteristic.