Marconi Instruments 2955 - Page 46

OPERATION
(2)
HELP
key.
Used
to select
the
20 dB
attenuator
and
600
H
dBm
accessory’
as
des-
cribed
under
‘HELP
Key
Operationh
TONES
key.
Used
to
select two
tone
operation
during
AUDIO
TEST.
AF
voltmeter
operation
(1)
Connect
the unit
under
test
to
the
AF INPUT
socket
(2)
Select
mode
RX
Q.
RECEIVER
TEST
is
written
on the
screen.
(3)
Press
BAND
PASS
(J)
to select the
300 Hz
to
3.4
kHz BP filter
or
press
LOW
PASS (i)
once
or twice
as necessar>^
to select
a
300
Hz
or
50
kHz
LP
filter.
(4)
To
read
AE volts,
press the
AC
DC
k-ey
(£)
until AC is
displayed,
(5)
To
read
DC
plus
AF volts,
press
the
AC
DC key
until
DC is
displayed.
The
50
kHz
filter
is
automatically
selected.
Note that the
DC
is
shown
with
no
sign
but
may
be
positive
or
negative.
(6)
To
select
dBV
or
dBr
(dB relative to
the entered
level), set
@
to
DISTN
OFF.
(7)
If
required,
change
between cBV
and dBr
by
pressing
the
dB
key
Q.
(8)
To
use the
optional
600 Q
dBm
accessory,
e.g.
for testing
telephone
lines,
connect
this
unit
between
the
,AF
GEN
OUTPUT
0
and the
AF* LTUT
0
sockets.
Press
the
HELP
key
(0
and
then continue by following
‘HELP Key
Operation'.
When
the
accessory
is selected. dBV
or dBr
changes-
to dBm.
Audio
test
During
AUDIO
TEST
operation.
.AF generator
operation
-
normally a
transminer
test
function
-
is
enabled
in
addition
to the
.AF voltmeter.
This permits the generator to be.
tuned
while
the
voltmeter
readincs are noted.
This mav
be used to
Dlot the characteristics
of
a filter
or
an
amplifier
which
Is connected
between
'the
AF
GEN OUTPUT
and the
AF
INTUT
sockets.
To
operate
in
AUDIO TEST,
proceed
as
follows:-
(9)
Press
AF
GEN
0
.
.AUDIO
TEST is
written
on
the screen and the
,AF genera-
tor
is
enabled.
(10)
Select
the
required
filter
as
in
(3).
(11)
Select
AC
or
DC
as in
(4)
or
(5).
(12)
Select
dBV
or
dBr
as in
(6)
and
(7).
3-22
46881
-622N
.
Apr.
88