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Getting Started
Figure 3-10
Row
connection examples
In addition to
expanding rows
in
a
mainframe,
it
is
also pos-
sible to isolate
card
rows
to
some
extent.
There
are factory-
installed
jumpers on
the
backplane
that
can be
removed
to
separate the general
purpose rows.
These
jumpers,
which
are
behind
the
Model 707A
front panel, are
between
slots
3
and
4
of analog bus #1
and
analog bus
#2.
Removing
these
jump-
ers effectively
separates
the
mainframe
into
two
3-slot
units.
(Jumper removal
is
described
in
paragraph
7.6.)
Another
isolation
method
is
simply
to
disconnect
the
SMB
coax jumpers between
adjacent
Model 7072
cards, for
exam-
ple.
These jumpers
(for
rows
A, B, G,
and H)
are
accessed
through
a
door on
top of
the
mainframe.
As
an example,
jumpers on
the
Model 7073
card
let
you
selectively
expand rows
on
the
backplane
to slots
on
either or
both
sides,
or completely
isolate
rows from
the
backplane.
External
expansion
External
expansion
within a single
mainframe
is
possible
with
user-installed
wiring
between rows and
columns
of
like
cards.
The
available
accessory cables
for external
connec-
tions are
listed
in
Table
3-3.
CAUTION
Connecting
dissimilar
cards together
often
degrades performance of
both
cards.
For example,
connecting
a
Model
7072
to
a
Model
7073
would
degrade
low
current switching
on
the
7072
and
high frequency switching
done
with
the
7073.
An
example
of
external
expansion
uses the
mainframe
as
one
6-slot unit
and, for
some
applications, as
two
3-slot
units.
After
removing
the
backplane jumpers,
just
use
external
row
jumpers between
the
cards
in slots
3
and
4
to select
the
desired configuration.
External
expansion of
the
cards
can
also
be used
to
imple-
ment
a
partial
matrix.
As shown
in
Figure 3-11
for
Model
7071
cards, a
column
connection
is
made
between
the
two
isolated
general
purpose
backplanes.
With
the
example
con-
nections
shown,
three crosspoints
must
be closed
to
source
(increasing the safety
factor),
but
only
one
cross-point
clo-
sure
is
needed
to
measure (recommended
for sensitive
instruments).
3-14
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