Marconi Instruments 2955 - Page 36

OPERATION
(F)
ACCESSORY
socket
DIN
7-pin connector
for
external loudspeaker
or
earphones.
Connection
does
not
disable
the internal
loudspeaker.
Control
of volume
is
by(J^.
LOW PASS
key.
Selects
a
300
Hz or
a
15 kHz
low-pass
filter.
(n)
AF
GEN OUTPUT
socket
BNC connector
supplying a
modulating
output in
the
range
20
Hz to 20
kHz.
Impedance
5
@
BAND
PASS key.
Selects
a
0.3
to 3.4
kHz
band-pass
filter.
(
13
)
VOLUME
control.
Controls the
volume
of the internal
loudspeaker
and
of
a
loud-
speaker
or earphones
connected
to
(?)
,
Modulation
meter
operation
—
To
measure
.AM
depth
or
FM
and DM deviation,
proceed
as
follows:-
(1)
Select
IX
0
.
TRANSMITTER
TEST is
written on
die screen.
(2)
Connect
the
transmitter
output to the
RF
IN/OUT
N
socket
0
. Mternatively,
connect
the
telescopic
aerial option
to the RF IN/OUT
BNC
socket
0
.
(3)
The
instrument
automatically tunes to
the
transminer’s
frequency. If
required,
the
transmitter
may
be tuned
for
minimum
or
zero
indicated offset
using the
2955
-
see
Transmitter
frequency
adjustment’ under
‘Applications’.
(4)
Press
SELECT
0
until the
LED
lights
above the
RF
IN/OLT
N*
connector
0
or
the
BNC
connector
0
.
(5)
Select
moduiation
type FM
(0,
A.M
(T),
or
^M
0.
if greater man
50%
-AM
is
applied,
there
is
a
possibility that
false readings
may
occur. Use
keyboard
tuning
of
the
modulation
meter
as
for ‘Transmitter frequency
adjustment'.
(6)
Press
B.AND
PASS
0
to select
the
0.3 to
3.4 kHz
BP
filter or press
LOW
Pass
(0
once or twice
as
necessary
to select
a
300
Hz
or 15
kHz LP
filter.
(7)
[f
required,
modulate the
transmitter’s
carrier by
connecting
the .AF GEN
OUTPUT
socket
0
to the microphone
input
of the
transmitter. Set
the frequency
and
level
as under
‘AF generator
operation’.
(S)
Read
the
disolaved % depth for
AM or
the
deviation and svmmetrv
for FM and
(
9
)
Adjust
VOLUTv'IE
control
0
to
monitor
the
demodulated
signal using
the in-
ternal
loudspeaker,
an
external loudspeaker
or
earphones
using the
ACCESSORY
socket
0
.
(10)
The
demodulated output is
available
at the
DE-.MOD
OUT
socket
on
the rear
panel.
3-1
2
46S81-622N
Apr.
83