Racal Instruments 9081 Maintenance Manual page 35

REAR
PANEL
ITEMS
Mains (AC) Voltage
Selector.
2.7 This
comprises two
slide switches, with a
screwed
locking plate,
for
selection
of
the appropriate a.c. supply voltage.
Instructions
for
voltage selection are given
in
para. 5.
1
.
Standard Switch.
2.8
This
toggle switch connects the
internal or
external
frequency
standard,
as
required.
If
the switch
is
inadvertently
in
the
EXTERNAL
position,
with no external standard
connected,
the
frequency
display
will
be blank.
Internal
Standard
Output
Socket
(BNC).
2.9
A
1MHz
reference output, derived from the
internal
frequency standard,
is
available
when
the
STANDARD
switch
is
set to
INTERNAL.
External Standard Input
Socket
(BNC).
2.10
This
socket accepts a
1MHz
external
frequency standard
input.
The
input
character-
istics
are
given on
page
Tech. Spec.
(2).
Audio Output
Socket
(BNC).
2.11 The output from the
internal
modulation
oscillators
is
available
at
this
socket.
The
level
is
nominally
IV
r.m.s. from a
600Q
source.
Frequency Standard and Adjustment.
2.12
Two
apertures are provided,
marked
COARSE
and FINE,
for
calibration of
the
internal
frequency standard.
The
FINE
aperture
is
for
use
with
the
9442
unit.
The
optional
9420M
uses
both
COARSE
and
FINE
adjustments.
A
calibration
procedure
is
given
in
para. 5. 41
.
Power
Fuse.
2.13
A
5 x
20mm,
glass
cartidge, anti-surge,
type
fuse
must be
used.
The
fuse ratings
are
marked on
the panel.
The
instrument
is
despatched
with the
188V/260V
fuse
fitted
and
a spare
94V/130V
fuse
is
supplied
in
the Accessories bag.
9081
&
9082
Vol.2
2-9