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FREQUENCY STANDARD
CHARIER
_2
1
.7
Customers
are offered a
choice
of
two
high
stability
temperature
controlled
frequency
standard from the
Racal-Dana
range,
or
an
unovened
oscillator.
Details are
given
on pages Tech. Spec.
(9).
The
high
stability units
should be serviced only by
Racal-Dana
or authorised
agents.
An
aperture
in
the
rear
panel provides access
for
calibration
of
the
frequency standard.
A
1
MHz
reference
frequency, derived from
the standard
in
use,
is
available from a
BNC
socket on the
rear
panel
.
1
.8
An
external standard,
which
will
over-ride the
internal
standard,
can be
applied via
the front
panel
'B'
input socket
for
use
on Frequency and
Period
mode.
A
front
panel l.e.d. Illuminates
when
the external standard
is
operating.
CARRYING HANDLE
1
.9
The
instrument
is
fitted
with a
combined
carrying handle
and bench
stand.
To
adjust the stand,
press
in
the
two handle
bosses
simultaneously
while
setting the
stand
to
the desired position.
MAINTENANCE
1.10
The customer
is
recommended
to
take
advantage
of the servicing
facilities
offered
by Racal-Dana
instrument Ltd.,
and
agents.
A
comprehensive
Maintenance Manual
is,
however,
available
for
purchase from Racal-
Dana.
P R
E
P
A_R
ATJIIN^ iPJi
1
1
AC
SUPPLY
VOLTAGE
SELECTION
Introduction
2.1
A
label
on
the
rear
panel shows the voltage range
to
which
the
instrument
is
set.
Six
pairs
of
voltage ranges are obtainable by appropriate
arrangement
of a
link
and
tappings on the transformer tag board.
A
two-position
slide
switch on the
rear
panel
enables
the user to select either the
upper
or
lower
range from
each
pair
(see Fig.
3o and
3b).
2.2
When
the selection
procedure
has
been completed,
a
label
showing
the
selected range
pair
must be
affixed
to
the rear panel.
Instruments
are
manufactured
with a
permanent
panel
marking
for
the
212-251V
range.
Five spare
labels
are supplied
in
the accessories
bag
for
use
if
another voltage range
has to
be
selected.
)
Voltage
Selection Procedure
2.3
(1)
Unplug
the
power
cable from the supply
and remove
the top
cover
(para. 2.9).
(2)
Refer
to Fig.
3a
or Fig.
3b and
note the
diagram
which
corresponds
to
desired
voltage range.
Note
that
the switch
diagram
is
drawn
as
seen from within
the unit.
(3)
Remove
the
snap-on
plastic
cover
plate from the transformer tag
board.
(It
clips
on
at the corners).
(4)
Using
a soldering
iron,
arrange
the
link
and
switch leads on the
transformer tag
board
to
conform
with the chosen
diagram.
Do
not disturb the neutral lead,
which
remains on
the
OV
tag at
all
times.
(5)
Refit
the plastic plate
to
the tag board.
(6)
On
the
outer
face
of the rear
panel
set
the switch
to the position
for the
required
upper
or
lower
half of
the voltage range,
and
attach
the
appropriate voltage
label
to
the
panel
.
(7)
Carefully
recheck
the
work
against the
diagram,
then replace the
top cover.
9902
&
9906 Vol
.
1
1-3
9902
&
9906
Vol
.
1
2-1
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