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EXTERNAL STANDARD:
The
I.e.d. illuminates
when
the external
standard
is
connected and
operating.
UNITS INDICATORS:
In
the
9906
four I.e.d's
provide appropriate
indication
to
show
the
units
for
interpreting
the display -
kHz/ps,
ms,
ns
and
seconds.
REAR
PANEL
ITEMS
1
MHz
O/P
Socket:
A
1
MHz
reference
signal
derived from
the
frequency
standard
in
use
is
available
at
this
BNC
socket.
Data
Output
Connector:
The
facilities
provided by
the
28-way
edge
connector
are
listed in
Table
1
on
page
Tech. Spec.
(10).
Power
Plug/Filter:
A
three-core
power
lead
(line
cord)
is
supplied with
the instrument.
Power
Fuse:
Fuse
ratings are
marked
on
the rear
panel.
A
surge
resisting
5
x
20mm
type must be
used.
Osc.
Adjust:
This
aperture provides access
to
the
calibration
adjustment
in
the 5
MHz
reference
oscillator.
Calibration must
be
carried out
in
accordance
with
Instructions
in
the
maintenance manual.
Voltage
Selector Switch:
This
switch
is
set
in
conjunction with
selected tappings
on
the
line
power
transformer.
Instructions
are
given
in
Chapter
2.
It
is
important
that the label
adjacent
to
the
switch shows
the
voltage
range
selected
.
9902
&
9906
Vol
.
1
3-5
POWER
SUPPLY
CHAPTER
4
0_P_E_R_A
T
l_N
G_
J
N_S_T_R_U
C
T
I
0_N
S
4.1
Before operating a
new
Instrument,
or at
a
new
location,
check
that the
line
voltage
selection
is
correct
(check
rear
panel
label)
and
that the
fuse has the specified rating.
FREQUENCY MEASUREMENT
4.2
In
this
mode
the
unknown
frequency
is
gated
to
the counter
decades
for
the gating period selected
by
the
chosen
Timebase
push-button
(n).
For
frequencies
below lOkHz
the use of period
mode
will
give greater
resolution.
(1)
Set the
POWER
switch
to
ON.
(2)
Set the following controls:-
(a)
Function switch
to
FREQUENCY
-
'A'
MAN.
(9902)
or,
on
the
9906,
select required
range,
VHF
or
HF.
(b)
The
'A'
channel
AQ^DC
switch
to
AC
or
DC,
as
required.
(c)
If
using
AC
mode
set
the
SENSITIVITY
control
initially to
the
maximum
clockwise
position.
(d)
CHECK/OPERAT^HOLD
switch
to
OPERATE.
(e)
DELAY
switch
to
OUT.
(3)
Connect
the
unknown
signal
to
the
'A'
input socket.
(4)
If
counting
is
not satisfactory adjust the
SENSITIVITY
control anti-
clockwise towards
the
lOmV
setting
until
a
stable
reading
is
obtained
.
(5)
Select
the
'n'
push-button
which
fills
the display, or
switch
to
AUTO
(9902
only)
for
optimum
resolution.
The
frequency readout
is
in
kHz.
9902
&
9906
Vol
.
1
4-1
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