Specifications

1. INTRODUCTION
A. THE
CLEAR-COM
CONCEPT
Clear-Com
is a
closed-circuit
in-
mic
input
lines
(200
ohms)
and
tercom
system
that
provides
high-
specially
designed
circuitry
make
intelligibility,
two-way
communica-
Clear-Com
channels
virtually
immune
tions
in
high-
or low-noise
envi-
to
RF and
dimmer
noise.
ronments.
A basic
intercom
system
contains
a
one-
or multi-channel
Clear-Com
Main
Stations,
Power
Sup-
Main
Station
interconnected
with
plies,
and
some
Remote
Stations
various
remote
headset
and
speaker
provide
an
auxiliary
program
input
stations.
with its
own
volume
control,
which
al lows
the station
operator
to
Clear-Com
manufactures
a wide
va-
monitor
external
audio.
riety
of
portable,
rack-mount,
and
custom-mount
intercoms.
All
are
Visual
Signal
Circuitry,
a
standard
compatible,
allowing
systems
to be
feature
on
most
stations,
allows
set up
according
to specific
needs.
the
user
to attract
the
attention
The
Clear-Com
System
interfaces
of
operators
who have
removed
their
with
virtually
any other
type
of
headsets
or
turned
off their
spea-
communications
systems
(call
Clear-
kers.
Con
or see
your
dealer
for info).
Depending
upon
the
type
of
Main
and
Clear-Com
Stations
normally
inter-
Remote
Stations
selected,
a maximum
connect
with standard,
2-conductor
amount
of Remote
Stations
from
12
shielded
microphone
cable;
they
(speaker)
to 100
(headset)
can
be
include
inputs
for
XLR-type,
3-pin
connected
along
one
mile
of wire.
connectors.
One
wire
in
the mic
Remote
Stations
bridge
the
intercom
cable
carries
DC
power
(28-30
line
at a very
high
impedance,
and
volts)
from
the
Main
Station
to
the
place
a minimum
load on
the
line.
remote
stations,
and
the
other
wire
Audio
level
remains
constant,
never
carries
the
audio
signal.
The
fluctuating
even
when
stations
shield
acts
as common
ground.
Au-
leave
or
join the
line.
dio termination
is required
at only
one
point
in
the intercom
system,
The regulated
DC
voltage
provided
and
is usually
provided
by
the Main
by
Main
Stations
and Power
Sup-
Station
or Power
Supply.
plies
enables
remote
stations
to
operate;
they
run
at minimal
cur-
Clear-Com
is a "distributed
ampli-
rent
(10
milliamperes
quiescent
for
fier
system:"
each main
and
remote
headset
stations,
20 ma
quiescent
station
contains
its
own
mic pream
for speaker
stations)
while
genera-
plifier,
power
amplifier
(for
head-
ting
extremely
loud
listen
volumes
set or
speaker),
and
signalling
(greater
than
110 dB
SPL).
The
circuitry.
Every
intercom
has Auto-
higher
voltage
and
low current
keep
matic
Headset
Detection,
a circuit
voltage
losses
to a
minimum
in long
that
shuts
off the
mic
preamp
when
lines.
If the
voltage
drops
due
to
the
mic or
headset
is
not connec-
the
addition
of
cable
or many
sta-
ted,
so background
noise
is
not
tions,
Clear-Com
equipment
conti-
increased
by an
unused
but
on-line
nues
operating
normally
with
less
(connected)
station.
Low-impedance
than
12
volts
available.