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Operation
4.4.5
Make/break and break/make LEDs
The
MAKE/BREAK
and
Bi^AK/MAKE
displays
each
have two
blocks of
LEDs
labeled
A-H
(one
for
columns
1-36, the other for
columns
37-72).
Refer
to
Figure
4-3.
Each
block
shows which
rows have been
selected for
niake/break
or
break/make
operation.
When
switching current
sources,
use
make/break
operation
to
keep
current
flowing
and
elimi-
nate
switching
transients.
When
switching voltage
sources,
use
break/make
operation
to
avoid
momentary
shorting of
two
paths
together.
The
LEDs
can be
turned
on
or off
by
pressing a
row
letter
key
and
the
MAKE/BREAK
or
BREAK/MAKE
key,
or
with an
optional
light
pen.
Note
that
selecting
a
row
for
break/make
de-selects
it
for
make/break and
vice
versa.
4.4.6
Light
pen
The
light
pen
is
an
optional input device
for
toggling
the
on/
off
states
of
crosspoint display
LEDs,
MAKE/BREAK
row
LEDs,
and
BREAK/MAKE
row LEDs.
One
light
pen
is
used
to
control the
LEDs
of
all
units
in
a
raaster/slave
system.
As
seen
in
Figure
4-4, the
light
pen
plugs
into
the
front
panel
of stand-alone or master
units.
Remove
the light
pen
by
pressing the button
on
the
connector plug while
pulling out
the plug.
Mount
the
light
pen
holder
on
the
left
handle of
the
Model
707A
by
tightening the alien-head
screw
shown
in
Figure
4-4.
To
toggle the
state
of
a crosspoint
LED
or
MAKE/BREAK,
BREAK/MAKE LED
with
the
light
pen, follow these
steps:
1.
Hold
the
light
pen
as
you would
an
ordinary pen.
2.
With
the light
pen
perpendicular
to the front
panel
overlay
at
the
desired
LED,
press the button
on
the
pen's
barrel.
3.
Proper usage
will
toggle
the
state
of
the
LED.
If
the but-
ton
is
pressed
while
not
on
an
LED,
the
message
LIGHT
PEN????
is
displayed
briefly,
then the
Model 707A
reverts
to
its
previous
display.
4-8
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