Service manual
IV.
Rm-120A
OPERATING
CONTROLS
&
CONNECTORS
The
RM-120A
controls
and
connectors
are
described
below
in
the
order
in
which
they
appear
on
the
FRONT
PANEL
from
LEFT
to
RIGHT.
Fo
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~~~~~~~~~~RM.120A
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1900
-48260)
Call
The
Call
push-button
activates
visual
signalling.
It
allows
the
inter-
com
user
to
attract
the
attention
of
operators
who've
removed
their
headsets
or
turned
off
their
speakers.
The
Call
button
can
also
con-
trol
the
speaker
or
mic
at
KB-112
Stations
set
up
for
remote
control.
The
Call
signal
follows
the
position
of
the
"Channel
Select"
switch;
if
you
using
Channel
A,
the
Call
button
causes
the
lamps
to
light
at
all
other
stations
using
Channel
A
(and
likewise
for
Channel
B).
When
the
Channel
Select
switch
is
set
to
"both,"
the
lamps
at
all
stations
on
both
channels
shine
simultaneously.
The
Call
signal
is
active
for
as
long
as
you
keep
your
finger
on
the
Call
button.
Receiving
Signals:
The
amber
Call
lamp
on
the
left,
for
Channel
A,
lights
when
any
station
on
that
channel
activates
the
Call
circuit.
The
amber
Call
lamp
on
the
right,
for
Channel
B,
lights
up
when
any
Channel
B
station
activates
Call.
They
operate
independently
of
the
setting
of
the
Channel
Select
switch.
Note:
an
internal
jumper
reverses
the
Call
function
for
use
with
KB-112
remote
control--
call
Clear-Com
for
info.
Channel
Select
This
3-position
toggle
switch
assigns
the
RM-120A
speaker/headset
moni-
toring
function
to
(1)
Channel
A,
(2)
Channel
B,
or
(3)
both
channels
(RM-120A
operator
can
talk/listen
to
stations
on
Channel
A
and
stations
on
Channel
B,
but
Channel
A
stations
cannot
talk/listen
to
Channel
B
stations--
unless
a
Party
Line
system
has
been
set
up
via
the
Main
Station).
Sidetone
Adi
The
sidetone
adjustment,
which
is
controlled
with
the
blade
of
a
small
screwdriver,
allows
the
RM-120A
operator
to
add
back
a
fixed
level
of
his/her
voice
in
the
speaker
or
headset,
regardless
of
which
channels
are
selected.
When
using
the
gooseneck
and
speaker
simultaneously,
this
control
should
be
turned
all
the
way
down
to
further
reduce
the
possibility
of
feedback.
Internal
Trimpots
(schematic
reference,
P5
and
P6):
One
sidetone
null
control
per
channel;
you
need
only
adjust
the
sidetone
once
at
the
time
of
installation
(if
at
all),
even
if
other
stations
subsequently
join
or
leave
the
intercom
system.
Adjusting
the
sidetone
does
not
affect
the
level
of
incoming
or
outgoing
signals.
(continued)
4