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r
:
I
Model 5245L
pulse.
Consequently,
when
a frequency
is
applied
to
the input of
the
decade
divider, the
first
binarydivides
it
by
two
(since
the
first
pulse switches the binary to
the
opposite state and
a
second
pulse
is
required to
return
it
to
its
original state)
and
again by
two in
the
second
binary
(making
a total division by four)
and
so
on,
with
an
expected
total division of
sixteen
at
the
output
of the
fourth
binary.
The
desired division by
ten
is
obtained
bya feed-ahead pulse to the fourth
bi-
nary
and feedback pulses to the
second and
third bi-
naries.
Therefore, after the
eighth input pulse is
received the binaries
wiII
be
in a
state as
if
they
had
counted
fourteen
pulses.
Then,
when
the
ninth
and
tenthpulses are
received the desired final
output
pulse
is
produced.
Operation
is
similar
to that described
for
the
decimal
counters
discussedin Paragraphs
2
-76
and
2-?? except that there
is
no
display
array
con-
nected
to the
binaries.
Note
that
A31
throughA34 are
suppliedwith a reset input sothat
only
a
certain
num-
ber
of
input pulses
to
the
decade
dividers are necessary
after reset before
an output
is
produced. Refer tothe
schematic
diagram Figure 7-24,
for circuit
details.
2.IT7"
TIME-BASE CONTROL ASSEMBLY
A35.
2-118.
GENERAL. The
purpose
of the
time-base
control is
to
a)
Iower the output impedance of the
10
MHz signal
from multiplier
A21;
b) select
a
f
requency
between
0.1 Hz
and
10
MHz as controlled
by
the TIME
BASE
switch,
and c)
provide a multiplied period sig-
nal
when
the
FIINCTION switch selection
is
between
10 and 100K
PERIOD
A\IERAGE. Inhibit
gates
?
thru
11
(CRB,
CR11,
CR14,
CR1?,
and CR20)
are normally
open;
a
control
voltage
to turn
one
of these gates
off
is
applied only
for
multiplied period
measurement.
Multi-period
gates
7
thru
11(CRg,
CR12,
CR15,
CR18,
and CR21)
are normally closed;
one
onlyis
opened
for
multiplied period measurements.
Selected
frequency
gates 21
thru
28
are
controlled by the TIME-BASE
switch.
2-Lt9.
SELECTED
FREQUENCY
CONTROL.
For
atl
ope
rating functions
except
PE
RI
OD
AVE
RAGE
C
Im
C
K,
gates
21
thru 29 are onfor the TIME BASE selections
listed in Table
2-4.
For example,
if
the TIME
BASE
switch
is
set
to
1
ms,
the control voltage
is
applied
to
gate
25, turning
it
on and
permitting
the
l
kHz signal
from
A30
to be amplified byQ11
and Q12;
the
ampli-
fied
l
kHz
is supplied as
the
selected
frequencytoA2l.
Section
II
Paragraphs 2-117
to
2-122
(For
PERIOD AVERAGE
CIIECK,
gate 21
is
on, re-
gardless of TIME BASE seleetionrandl00kHz
is
sup-
plied as the selected frequency.
)
2-120.
MULTIPLIED PERIOD CONTROL. Control
voltages
for
gates
?
through
11
are
supplied only
for
multiplied period measurements, as listed in
Table
2-5.
These
control voltages select
one
to give
steps
of
decade
division
for
the period
signal supplied by
A21.
Example
1:
The FUNCTION switch
is
set to
IO-PERIOD AVERAGE; gate
control
11
is
on,
turning
off inhibit
gate 11 (to prevent
further division
of
the
signal from
4.26)and
turning
on
multi-period
gate
11;
the amplified period signal from
Q1
is
passed
thru
CR21, divided by ten
in
A34,
and supplied
thru
Q10
as the multiplied period
signal.
Example
2:
The
FUNCTION switch
is
set to IK-PERIOD
AVERAGE;
gate control 9
is
on, turning off inhibit
gate
9
and
turning
on
multi-period
gate 9; the amplified period
signal
from
Q1
is
passed
through CR15,
divided
by
ten
in
432,
passed
by CR1?, divided in A33,
passed
by
CR20, divided
in
A34,
and supplied through
Q10
as
the multiplied period signal.
Table
2-5.
Multiplied Period Control
Gate
Control
On
Function
Switch
7
B
I
10
11
lOOK
PERIOD
A\TE
lOK PERIOD
A\TE
lK
PERIOD AVE
1OO
PERIOD AVE
10 PERIOD
AVE
2-12t.
GATING
CONFLICT.
A few combinations
of
TIME
BASE
and FUNCTION
switch
selections produce
overlapping decade-divider
requirements. For
ex-
ample,
a
TIME BASE selection of
0.
1s
and
a FUNC-
TION selection
of
10K-PERIOD AVERAGE turns
on
gate
control
23
and gate
control
8;
the expected
selected
frequency
of 10
Hz is not
supplied
through
CR16-Q7
since
the frequency-dividing chain
is blockedatCRll;
the
counter display
is
therefore meaningless.
An
alarm for
unallowed
switch combinations
of this sort
is
given by
the lighting of an
asterisk (*)
at the right
end
of the front
panel
display.
The
asterisk
is
also
used
to indicate two other
non-useful
control
combin-
ations: 1)TIME
BASE
of 0.1 psand frequencyFUNC-
TION, and 2) TIME
BASE
of
10 SEC and
PERIOD
function.
The
asterisk
lamp (in A9)
is
controlled by
switching
contacts on
both
the
TIME BASE
and
FUNC-
TION switches.
2-L22.
CIRCUITS. Refer to the
schematic diagram,
Figure 7-25,
for circuit details.
Most of the gates in
A35
are of
the
type described
in
Paragraph 2-6, but
gates 28
and
29 are
two-diode AND gates, described
in
Paragraph
2-94.
The
inhibit
gates (CR8, CRl1,
CR14, CR1?,
and
CR20)
are similar to
conventional
AND gates except that
they
are
always on
(forward-
biased
diode)
in the
absence
of the control voltage
and
off
(reverse-biased diode)when the control voltage is
applied.
Table
2-4.
Normal Time Base Control
Gate
Control
On
Time
Base Switch
2l
22
23
24
25
26
27
28
29
10s
1s
0.
1s
10 ms
1ms
0.
1ms
10
ps
1
trts
0.
1ps
02349-1
2-23
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