Service manual

1. INTRODUCTION
1. A. The Clear-Com
Concept
Clear-Com
is a closed-circuit
intercom
dimmer noise.
system
that
consistently
provides
high-
clarity,
two-way
communications
in
high-
Clear-Com
main stations,
power
supplies,
noise
and
low-noise
environments.
A
and certain
remote
station
each
have an
basic
system
consists
of
a single-
or
auxiliary
program
input
with
its own
multi-channel
power
supply
or main
sta-
volume
control,
which
allows
an external
tion
connected
to
various
single-
or
source
to be
fed to
the intercom
system.
multi-channel
remote
stations.
Visual
Signal
Circuitry,
a standard
feature on most main and remote
sta-
Clear-Com
manufactures
a wide
variety
of
tions,
allows
the
user
to
attract
the
both
portable
and
fixed-installation
attention
of operators
who have
removed
units.
All
are compatible
with
each their
headsets.
other
(Clear-Com
can
also interface
with
other
communication
systems;
see Section
Depending
upon the
type
of main
and
IID
or ask
your dealer
for details).
remote
stations
selected,
a maximum
number
of remote
stations from
13 (all
Clear-Com
stations
are
interconnected
speaker
stations)
to 100
(all
headset
with two-conductor,
shielded
microphone
stations)
can be
distributed
along
a
cable,
using
3-pin
XLR connectors.
One
mile
of
wire.
Remote
stations
bridge
wire
carries the
DC power
(28-30 volts)
the
intercom
line at
a very high
impe-
from a
main station
or power
supply
to
dance, and
place
a minimum
load on
the
all
remote
stations,
and
the other
wire
line.
Audio
level
always
remains
con-
carries
audio
information.
The
shield
stant,
and does
not
fluctuate
as
sta-
acts
as a
common ground.
Only one
ter-
tions
leave
or join
the network.
mination
is needed
throughout
the
inter-
com
network,
and
is located
in a
main
The
28-30
volts
DC provided
by
main
station
or
power supply.
stations
and
power
supply units
enable
remote stations
to operate with minimal
Clear-Com
is
a distributed
amplifier
current
(10 milliamperes
quiescent
for
system;
each main
and
remote
station
headset
stations,
20
mA quiescent
for
houses
its own
mic preamplifier
(for
speaker
stations)
while generating
ex-
headset
or speaker)
and signalling
cir-
tremely
loud
listen
volumes
(greater
cuitry.
The
Automatic
Headset
Detection
than
110
dB SPL).
The
higher
voltage
circuit
shuts off
when any
station's
mic
and low
current keep
voltage
losses
to
preamp
is disconnected,
so
background
an absolute
minimum
in
long lines.
If
noise on
the line
is not increased
by
an the
voltage
drops due
to the addition
of
unused yet
on-line
station. Low-impe-
great lengths
of cable
or many
more
dance
mic
input
lines
(200
ohms)
and
stations,
Clear-Com
equipment
will
con-
specially
designed
circuitry make
Clear-
tinue operating
with
less than
12 volts
Com
channels
virtually
immune
to
RFI and
available.