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E L E C T R I C A L P R I N C I P L E S
97
-
N
n
O
m
l
Indicator
Block
Figure
94.
Indicator Lights
used t o indicate the counter reading a t any time by
indicating which triggers are
ON.
One row of
lights applies to each counter position. The bottom
view of the chassis indicates the ,terminal connec-
tions.
As an example of the circuits for
a
complete
counter chassis, see the circuit diagram for chassis
K,
the 5th and 6th counter positions of rhe multi-
plicand counter (Sections 47 and 48 on wiring
diagram).
Note that the nine filaments are in
series across the 111 volt A.C. line, placing 12.8
volts across each filamenr. All counter chassis are
che same regardless of where they are used.
If
carry circuits are necessary, the tubes controlling
carry are mounted in separate chassis. N o carry
circuits are used in the multiplier or multiplicand
counters; only the product counter requires carry
circuits.
Observe that all counters use high-speed triggers.
Since counter read-in may be a t either high or low
speed, i t is necessary to employ high-speed triggers
throughout.
Indicator Blocks
Neon indica,tor lights are used throughout the
electronic unit t o indicate the status of various
triggers. The light is wired to glow when the cor-
responding trigger is in the
O N
status. Figure 94
shows how the indicator light is connected to a
trigger. As long as the trigger is
OFF
(tube 1 con-
ducting), the anode of tube 1 (point A ) is at +40
volts, and there are 40 volts impressed across the
neon bulb since the bulb is connected between
ground and the anode of tube 1 through resistor
R.
This bulb will not glow, however, until a t
least 90 volts are impressed across it.
When the
trigger goes
ON,
the potential at the anode of tube
1 rises to + I 3 6 volts, and the neon bulb will glow,
indicating that the trigger is ON.
The I megohm resistor
R
limits the current
through the neon bulb, isolates the anode of tube
1 from other circuits, and thus prevents capacity
coupling in the cables.
As a word of caution, it should be pointed out
that the neon bulb will glow when the po.tential
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