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98
T Y P E
6 0 3
E L E C T R O N I C
M U L T I P L I E R
at point A is over f 90 volts regardless of the trig-
Brush
makes
ger status. For example, if the filament of a trig-
here
3
9
8
7
6
5
3
2
I
9 Pulses in ryn-
ger tube is burned out, neither tube can conduct.
L=)
0
a
0
L=)
C3
~ c h r a n i s r n w l t h p ~ c h
/ ~ 3 . ~ ; 4
index
However, the indicator light glows, indicating
that the trigger is
ON.
Sometimes this can be used
to detect
a
faulty -trigger tube.
The indicator bulbs are mounted in a block
which can be plugged into a socket. An extension
cable is provided to permit viewing indicator lights
from the rear of the chassis. The layout of the
bulbs in a block is shown by the insert in Figure
94. Note that there are ten bulbs in the block.
The numbering is designed to permit use of a stan-
dard block in all applications.
The horizontal
numbers between the bulbs ( 1 , 2 , 4 , 8 ) refer to the
digital value of triggers used in counters while the
numbers along the edges of the block merely rep-
resent the bulb number. When the socket is used
in locations other than counters, it is ordinarily
mounted vertically so that the numbers on the
outer edges can be read.
In these cases the left
side is counted first, and number 6 is the first bulb
in the row to the right.
To avoid confusion, it is recommended that on
the indicator blocks used in counters the outer
numbers be blacked out with masking tape or
crayon.
Counter
Read-In
from Card
Reading into an electronic counter from a card
requires that the electronic counter receive a num-
ber of negative pulses equal to the value of the
digit punched in the card. The method of doing
this is illustrated by the block diagram in Figure
91.
A
set of CB's provides 9 positive pulses which
are fed t o a switch tube. The pulses from the CB's
have no effect, however, until the switch is "un-
locked" by the trigger, and consequently no nega-
tive pulses can pass through from the switch tube
to the counter until the read-in trigger is turned
ON.
(A tube inverts a pulse so that the positive
pulses from the CB's pass to the counter as nega-
tive pulses.)
9
3
Po8ilive
Nap.
Swilch
Pulses-
Counler
Tube
cB1s (Index time)
T
T 0 + 4 0
( " 3 " hole in card)
Figure 95.
Block Diagram of Counter Read-in Circuits
When a brush drops through a hole in the card,
the read-in trigger is turned
ON,
and the switch
tube is "unlocked" so that it can start passing
pulses. If, for example, the brush drops through
a 3 hole, the CB's will make only 3 more times in
that cycle and only 3 pulses will be passed to the
counter.
The trigger is necessary to provide a
means of maintaining the switch tube in a con-
ductive state until the end of the cycle, because
the impulse from the hole in the card has a dura-
tion of only 0.3 of a cycle point on the index.
Before a new cycle is started, the read-in trigger
is cancelled
OFF
to prepare it to accept a new read-
ing. The block diagram does not indicate the actual
connections, but these can be found in the com-
plete circuit for read-in control of one counter
position shown in Figure 96.
Observe that the control grid of the pentode
switch tube is tied directly to the grid of tube 2
of the trigger, so that the grid of the pentode fol-
lows the grid of tube 2 of the read-in trigger in
potential.
As long as the'trigger is
OFF,
as indi-
cated in Figure 96, the potential at point
G
is -30
volts and the pentode switch is cut of?. When the
trigger goes ON, point
G
rises to cathode potential
and so does the control grid of the pentode, there-
by conditioning the pentode to conduct. The posi-
tive pulses on the suppressor of the 6SK7 can then
be inverted to negative entry pulses for the
counter input. The voltage shift at the anode
of
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