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Model 5245L
I
l
Figure
2-19.
Sampling
Control Block Diagram
of
both the
gate
flip-flop
and
amplifier
Q10
are
com-
bined,
then
amplified by A11 to drive the front-panel
GATE lamp;
the
GATE lamp
is
therefore
on
during
the gating signal plus 30
milliseconds;
this
ensures
a
visible flash from
the
lamp
even
for very short
gates.
2-98.
CIRCIIIT
DETAILS.
Refer
to the
schematic
diagram, Figure
7
-19,
for
circuit details. AII
cir-
cuits are conventional; flip-flop operation is described
in
Paragraphs 2-15
and
2-16,
and one-shot
multi-
vibrator
operation
is
described
in
Paragraphs 2-19
thru 2-22.
The steering amplifiers
(Q2
and Q3)
are
common-base
amplifiers;
one
amplifier
(whose
col-
lector
is
connected
to the collector of the conducting
flip-flop transistor)
cannot operate
because
of
low
collector voltage; the other amplifier
(whose
collec-
tor is
connected
to
the
collector of
the
cut-offflip-flop
transistor) amplifies the
gate
triggering pulse
and
supplies
it
to the receptive
flip-flop transistor.
2-99.
SAMPLING CONTROL ASSEMBLY
A23.
2-100.
GENERAL. During normal operation, the
sampling control assembly receives
the
positive
trans-
fer
pulse and
the
sampling
trigger
pulse
from
A22;
its
outputs
are
a)
the amplified
and
inverted transfer
pulse,
b)
reset
pulses
for
the
decimal counters
and
decade
dividers,
and
c)
the holdoff signal which pre-
vents
retriggering
of
the
gate
flip-flop
tn
A22.
Refer
to
the block diagram, Figure 2-19, during the fol-
Iowing explanation.
g.?31?;'
2-101.
TRANSFER
PULSE.
The positive transfer
pulse
is
amplified without inversion by Ql, then amp-
Iified
and
inverted by
Q2.
During manual reset (RE-
SET
pushbutton pressed or FUNCTION or TIME-BASE
switches operated)-15volts
is
amplified
and
inverted
by
Ql,
then amplified
and
inverted by
Q2
to
produce
a manually generated equivalent of the
transfer
pulse.
Action
of other circuits
resets
all
decimal counters
to zerobeforethe
reset contacts
open;
then
the
voltage
on
the transfer pulse line transfers the zero
count
to
the front-panel numerical display.
2-t02.
RESET.
The
negativetransitionof the
samp-
Iing trigger pulse
from
A22 normally
triggers
the
sample-rate one-shot multivibrator and starts opera-
tion of all sample-rate control
circuits.
Multivibrator
feedback
is
through quick-recovery
amplifier
Q?,
capacitor C4,
and
emitter follower Q5. The
sample-
rate outputpulse duration
is controlled bythe SAMPLE
RATE
potentiometer andis variable
between 55
milli-
seconds
and
5 seconds.
When
the
SAMPLE-RATE
control
is
operated
to the HOLD position (completely
clockwise), the multivibrator provides a
eontinuous
output. An amplified
output
is
taken
from
Q?,
differ-
entiated
(leading
edge
is
selected), amplified
by
QB,
and supplied
as
the DCA
reset pulse
and
the DDA
reset
pulse.
If
manual
resetoccurs during the sample-rate
multivibrator
cycle, the multivibrator
is
quickly re-
turned
toits
quiescent state as
a result of the -15volt
input through
CR3.
Section
U
Paragraphs
2-98
to
2.102
ig-ioi3gr-,r
A22
(6)
OUTPUT
OF
TRANSFER MVB
I
RESEr
I
-.1-
Lo-lli .--''
Lo_ui
A3StE(R-9
t/2)
J|
(22)
INHIBIT
SIG
FROM
DR
A2?el
SAMPLING
TRIGGER
L
PART OF
A3
PART
OF
A3
Aro-
A
t7
DCA RESET
A
3t
-A34
DDA
RESET
A22
(7'
HOLDOFF
PULSE
PULSE
-t5v
CLOSED
MAX
CW
TO
53
IOPENS
LINE
MAX
INHIB
INPUT
2-2L
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