Pilot Tone Indicator; Speaker Protection - JBL Intellivox ADC V90 Mark II Instruction Manual

HOLE FOR
SECURITY SCREW
REAR OF
GRILL
LOCATING HOLE
WITH RETAINING CLIP
fig.11 - Securing the front grill
Insert a screw through the larger hole in the corner of
the grill rear flange by feeding it from the inside of the
flange, so that the thread of the screw protrudes from the
rear of the grill. Push a retaining washer (supplied with
the screws) over the screw thread, and up against the
metalwork to retain the screw in position. Repeat for the
other three corners.
Push the grill into place using the locating spigots as
previously described. Insert the hex key supplied through
holes in the grill itself to tighten the security screws into
the M4 tapped holes.
PILOT-TONE INDICATOR
In many PA/VA systems, a high-frequency pilot-tone is
continuously fed to the loudspeakers for load monitoring
purposes. This permits load and cable integrity to be
constantly verified. A LED is fitted to the front panel of the
ADC range of speakers, which illuminates on detection of
a pilot-tone. The LED is visible with the grill installed, and
is a useful check that the system is operational.
The JBL AXYS PB-400 and PB-800 amplifiers include
a suitable pilot-tone generator; other manufacturers'
equipment may also be suitable. The pilot-tone should
be in the frequency range 20 to 23 kHz, and of at least 6
Vrms amplitude (note that this level is not dependant on
the tap setting, the detection process is most sensitive for
frequencies around 21 kHz) for the LED to illuminate. Pilot-
tones of other frequencies and/or levels may be used if the
fault monitoring system demands them; the illumination of
the LED is not essential for such a system to operate correctly.
16

SPEAKER PROTECTION

In a PA/VA system, it is important that the failure of a single
loudspeaker does not incapacitate the rest of the system.
M4 TAPPED HOLE
The ADC range of speakers incorporate three protection
systems to prevent this.
FRONT OF
SPEAKER
1. The glass fuse is designed to protect against excessive
LOCATING SPIGOT
2. ADC units also incorporate a separate thermal fuse in
3. A ceramic connector ensures that the terminal will not
JBL Professional
current being drawn by the unit. The fuse is a standard
20 mm diameter 1 A anti-surge type. Only replace this
with a fuse of the same type and rating. In the event of
the fuse needing replacement, remove the protective
cap from the fuseholder. The fuse can be removed from
the holder by inserting a small screwdriver or similar
through the holes in the top of the holder. Refer to
fig.12.1 (Model V90) and fig.12.2 (Model H90).
series with the 100 V/70 V input. This is intended as
fail-safe device, which goes open-circuit if the internal
temperature becomes excessive, such as would occur
in the event of a fire. Thus a local fire which damages
a single speaker on a system does not cause other
speakers elsewhere to fail, as the damaged unit is
removed from the speaker circuit.
melt in a fire situation and short out the audio line.
fig.12.1 - Fuse location (Model V90)
fig.12.2 - Fuse location (Model H90)
® Intellivox ADC Installation Manual
201402/ADCIM