Instruction manual

INSTALLATION
I Clear-CoM
CS-222
2-Channel
Main
Station
SECTION
2
INSTALLATION
OF
THE
CS-222
2-CHANNEL
MAIN
STATION
2.1
INSTALLATION
OVERVIEW
The
CS-222
is
a combination
of
a very
versatile
intercom
station
and
a system
power
supply.
Installations
can
vary
depending
on what
features
are
used.
The
fundamental
concept
of Clear-Com
Party-Line
intercom
is that
all stations
provide
high
impedance
current
sourced
signals
into a
single
common
system
termination.
The line
drivers
in a station
have
a source
impedance
greater
than
10
KOhms.
The termination
of an
intercom
line
(or channel)
is a 220
Ohm
resistor
in series
with
a
4.7 KOhm
that is
paralleled
with
a 10
uF capacitor.
The
impedance
of the
network
at
audio
frequencies
is
220
Ohms.
The
DC
resistance
of
the
network
is
5 KOhms.
The
high
DC resistance
allows
a CALL
voltage
to be
placed
on the line
without
drawing
too
much
current.
A
CALL
signal
is a DC
voltage
greater
than
10 volts
on the
line.
The
DC source
for
this
CALL
signal
is
also
a current
source
there
by providing
a
high
impedance
and
not affecting
the audio
signal.
The
receive
or
"listen"
section
of
stations
contain
a
'hybrid
null'
circuit
that
attempts
to
reject
(null)
any
"talk"
signal
being
sent
by
that station
on
that
channel.
The
'hybrid
null' circuit
depends
on
a known
impedance
on
the intercom
line
to accomplish
this.
Variations
in
impedance
on the
line upset
the 'null'.
Clear-Corn
main
and some
remote
stations
provide
switch
selectable
termination
networks
on
all intercom
output
lines.
It is up
to the user
to determine
where the
termination
will be
provided.
An unterminated
line will
cause
excessive
levels,
possible
oscillation
of
line drivers,
and
sever
unbalance
of
hybrid
null
networks.
A
double
or multiple
terminated
line will
cause
low
levels
and
sever
unbalance
of hybrid
null circuits.
CAUTION:
All
Clear-Corn
Intercom
lines must
be
terminated.
Care
must
be
taken
not to
fall to
terminate
or to
'double'
terminate
a line.
All unused
intercom
inputs
must
be
terminated
to keep
the
line
drive
circuits
stable.
CLEAR-COM
STATION
TYPES:
Clear-Corn
party-line
intercom
stations
all
fall
into one
of
four distinct
categories
that
relate
to system
powering
and
termination.
The
four types
are
as
follows:
A.
MAIN
STATION:------
Supplies
system
power
for
external
stations.
Provides
switch
selectable
terminations.
B. MASTER
STATION:
- Contains
a power
supply
just
for
itself.
-
Provides
switch
selectable
line
terminations.
C.
REMOTE
STATION:
- No power
supply.
Derives
power
from
the Intercom
line.
- May
or may
not have
terminations.
D.
POWER
SUPPLY:
--- Supplies
system
power
for
external
stations.
--- Provides
switch
selectable
terminations.
11/90
Rev.
1.0
Page
9