AXYS H90 Panduan Instalasi - Halaman 14

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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. An 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 grille installed, and is

a useful check that the system is operational.

The 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 19 to 25 kHz, and of at least 5 Vrms amplitude

(relative to the 100 W tap setting) 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.

In a PA/VA system, it is important that the failure of a single

loudspeaker does not incapacitate the rest of the system.

The ADC range of speakers incorporate three protection

systems to prevent this.

1. The glass fuse used to select the internal transformer

tapping is designed to protect against excessive 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 fuseholder from

the PCB (noting the tap setting). 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. 9.1

2. ADC units also incorporate a separate thermal fuse in

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.

3. A ceramic connector ensures that the terminal will not

melt in a fire situation and short out the audio line.

AXYS

Intellivox ADC Installation Manual

200905/ADCIM_v1.0