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System Verification and 1toubleshooting
3-9.
Switch/Lamp Identification and Description
Figure 3-2 illustrates Maintenance Panel switches and lamps.
The
shaded numbers
on the right side of figure 3-2 identify
the row
number of
lamps or switches and are used in
table 3-2 as an aid
to locating the switch or lamp.
The I/O overlay is shown in fig-
ure 3-3. When referring to a switch or lamp, this manual uses the
name physically
marked on the equipment.
The name is quoted in
capital letters to indicate it is an
equipment
marking.
There
are three types of switches on the panel as follows:
a.
Bistable switches.
These switches
have two
positions,
and
can
remain in
either the up or the
down position.
In the
down
position they have
no effect on normal
computer func-
tioning, and they are left in this position except when their
particular function is required.
In figure 3-2, the bistable
switches can be
identified by the fact that they are in
the
down position.
b.
Two-position
spring-return
switches.
These
switches
are
pressed down when their function is required.
When released,
they return to the up position.
c.
Three-position spring-return switches.
These switches have a
center-off position.
'rhey are pressed up or down to
produce
the desired function.
When released, they return to the cen-
ter position.
All switches
of this type are in
row 12
of
figure 3-2.
Lamps which
display register contents are lighted when
the par-
ticular
position
of
the
register
contains a binary 1.
Lamps
which display
the state of a signal are lighted when
the signal
is
in the
asserted state.
That is,
a lamp is lighted
when a
"not" signal is low;
for other signals,
a lamp is lighted
when
the signal is high.
3-10.
Operating Precautions
The operating system, if in use, may cause unexpected changes
in
computer
functioning when the Maintenance Panel switches are ac-
tuated. These unexpected changes
result
from
such
factors
as
stack overflow, etc.
Therefore, the operator should be thorough-
ly familiar with the operating system before
attempting
to
use
the Maintenance Panel.
3-6
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