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Model 5245L
lighted, the lamp
associated
with
the
noncon-
ducting
transistor
is dark.
Typically, volt-
ages
will
be as shown.
Since the
transistor
associated
with the dark lamp
is
not conduct-
ing, no current
is
flowing in the
circuit of
the
dark lamp,
and
voltage across
it is established
(a)
by the circuit of
the conducting lamp
and
its
transistor,
and (b)
by the
voltage on
the
collector
of
the
non-conducting transistor.
This voltage is
not
high
enough to
fire
the
dark
lamp.
(2)
When
the
binary
shown
in Figure 2-8A
changes
state, the voltage
on
the
collector
of
transistor
A
(now conducting)
drops
to -10
volts, while
the
voltage
on the
collector
of
nonconducting
transistor A rises
to
+19
volts. Withtransis-
tor A
turned
off, current
through
lamp A de-
creases,
and
the voltage
at the junction of
the
two lamps
rises.
Since
Iamp
A cannot
fire
until
ionized, voltage
will
continue
to rise until
the
?0-volt firing level
is
reached;
the
junction
will
reach approximately
?3
volts during
the
ioni-
zation period. After
the
dark lamp
fires,
the
voltage across
it
stabilizes at
about
55
volts,
and
since the voltage across the other
lamp
is
now
reduced
to
38 volts, the other
lamp
extinguishes.
(3)
Circuit
state after lamp A has
fired is
shown
in
Figure 2-8A-2;
it is
the
mirror
image
of
that
shown
in Figure
2-8A-1.
b. Lamp Circuit with Diodes. The
steady, or
stora
it is
indicated in
Figure
2-88-1.
The
diodes
are
forward-biased,
eff
ectively connecting the lamps
in
parallel
and
clamp-
ing them to
approximately
-1.5
volts.
One lamp is
conducting, the other lamp
is dark.
Since
both lamps
are
clamped
to -1.5
volts, regardless of the state of
the
binary,
there
will
never
be
sufficient voltage across
the dark tight
to
fire it
and
it
wiII
remain dark until
1)
the diodes
are reverse-biased
and
2)
there
is
con-
duction through the
transistor in
whose
collector
cir-
cuit
the
lamp
is
connected.
(1) When the gate closes at the completion of
the
counting period (see Paragraph 2-95)
a
-29
volt transfer
pulse
(see
Paragraph 2-99) is
applied to the binary diodes, reverse-biasing
them.
With the
diodes reverse-biased,
the
lamps are
disconnected
from
each
other,
and
the
circuit
for
each lamp
is
now completed
through
its
associated
transistor.
(2)
If
the
state
of
the binary
is
the
same
as
that at the
end
of
the
previous
counting
period,
the lamps '(see', the
voltages required
to
maintain them without change.
If,
however,
the
digit
is
such
that the binary state
is
changed, the lamps change
state.
With
the
diodes reverse-biased,
circuit
action
is
the
same
as
that
described
in
subparagraph
a.
Condition
of
the
circuit
during the initiat
period
of
the transfer pulse
when
voltage
across the dark lamp
is
increasing is indi-
cated
in
Figure
2-BB-2; circuit
condition
after the
lamp has fired
is
indicated
in Fig-
ure
2-BB-3.
02349-
1
Section
II
Paragraphs 2-36
to
2-40
c.
Disabling the Storage. Whenthefunctionselector
is
set to MANUAL
or
theSTORAGE
switchon the rear
panel
is in
the off
position, the storage feature is
disabled. Circuit
action
is
then described
in
sub-
paragraph
a.
2-36.
BAStC COUNTER FUNCTtONS.
2-37,
GENERAL.
a.
The basic counter circuits are arranged to pro-
vide
several functional
modes
of operation.
Each
arrangement includes
a
main AND gate with 1)
a
signal input and 2)
a
control
input,
or
gating signal.
Following
the
maingate is
a
cascaded
series
of
decimal
counters which accumulate
and
display the total num-
ber of
pulses
which pass through the main
gate.
The
various
modes
of
operation
are
discussed
in
Para-
graphs 2-36 through 2-41.
b.
Circuit
sequence
in
the
various
modes
of opera-
tion is similar:
pulses pass through
the main gate
to
the decimal
counters
for
a
predetermined time, are
counted
and
displayed. The difference
between
ar-
rangements
is
in
1)
the source of the pulses
counted,
and
2)
the source
of
thegatingsignalwhich establishes
the
length of time during which the main gate is
open
to pass pulses to the decimal counters.
2-38.
TOTALIZING.
In
the totalizing
mode
(see
Figure 2-9A),
the
gate
flip-flop is
controlled by
the
FUNCTION switch
when
it
is in
the
MANUAL
START
or
MANUAL STOP
positions.
The
decimal counters
count
the total
number
of
input pulses
applied
while
the main gate
is
held
open
with the FUNCTION switch
in
the
MANUAL START position. SwitchingtheFUNC-
TION switch to the MANUAL
STOP
position
closes the
main gate
and
the
number
of
pulses which
came through
the
main gate while
it
was open
are
displayed.
2-39.
FREQUENCY
MEASUREMENT.
The circuit
arrangement
shown
in
Figure
2-9B permits control
of
the main gate
by
the counter time
base.
The
gate
is
opened
for a
controlled
time,
therefore the accumu-
Iated count represents
the number
of input cycles or
pulses
during this
time.
Controlled
intervals
are
from
10
seconds
down
to
1
microsecond
in
decade
sub-
multiples,
selectable
with
the
front
panel
TIME
BASE
switch.
The
decimal point
is
automatically positioned
and the
readout
is in kilohertz or
megahertz
with
the
units in line with the digital display.
2-40.
PERIOD
MEASUREMENT. The arangement
shown
in
Figure 2-9C
provides
the
meansformeas-
uring the period
of the
input
signal.
The
period of
a
signal
is
the time required for the
completion
of
one
cyclel
the counter displays the time
in
seconds,
milli-
seconds
or
microseconds.
The
period measurement
is
obtained
by making the duration of tfie
gating
signal
equal to the period of the input signal, and counting
a
train
of
pulses supplied
bythe
counter
time base.
The
displayed count
is
the number of time-base
pulses
which
occur during
one
period of the input signal. For
multiple period measurements,
Figure 2-9D,
the
input
signal
is
divided
bythe
selected
decadefactor
so
that the gating signal
is
the selected multiple of
one
2-g
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