58
SPECIAL
DEVICES
the sort magnet at 9 time through the card matching
commutator. This sorts the detail card into the 9 pocket.
Under regular sorting conditions, the OA4G trigger
tube ceases to conduct when the center brush on the
selector commutator opens its main anode circuit after
12 time each cycle.
In
this instance, however, the
N/c
A point of the card matching relay A shunts
around the outer and center commutator brushes via
MCM-R2, thus keeping the
OA4G trigger tube con-
tinuously ignited. This automatically sorts all successive
detail cards into the 9 pocket along with the first detail
card.
Although the
OA4G trigger tube remains contin-
uously ignited while successive detail cards are passing
through the machine, the
SOrt
magnet
is
de-energized
between 12 and 9 time on each cycle
so
that there will
be
no conflict with the mechanical armature knockoff.
This de-energization
is
accomplished
by
introducing an
additional bias voltage in the cathode circuit of the
2516 power tubes which control the circuit to the sort
magnet.
This voltage
is
obtained from a voltage divider con-
sisting of a 1 megohm resistor and
a
.5
megohm
re-
sistor connected in series across the DC machine circuit.
By
referring to Figure 41, it
can
be
seen that any volt-
age drop across the
.5
megohm resistor
is
applied to
the cathodes of the 2516 power tubes through octal
plug pin 8. This voltage
is
of a positive value in
re-
spect to the zero or negative
side
of the DC circuit and,
as
such, drives the cathodes
of
the 2516 power tubes
positive with respect to the negative side of the
DC
circuit.
When
these cathodes are
driVt'n
positive in this
manner, they become more positive than their control
grids. This in effect means that the control grids are
then negative with respect
to
their cathodes; there-
fore, the tubes cease
to
conduct and the sort magnet
is
de-energized. (See principle 7 in the Type 82 Circuit
Description. )
The
.5
megohm resistor
is
shorted
by
the card match-
ing commutator between 9 and 12 time, thus removing
the bias from the cathodes
by
connecting them directly
to the negative side of the circuit. This allows the
2516
power tubes to conduct and energize the sort
magnet at 9 time of each cycle
as
long
as
the OA4G
trigger tube remains ignited.
Sorting
Master
Cards
When
a master card
is
sensed
by
the card brush,
the starting anode of the MCM
OA4G tube
is
driven
positive, thus firing the tube and picking up the card
matching relay A (Figure
41).
This relay then holds,
through the
500 ohm resistor, the
N/O
relay A points,
and the center and outer brushes on the selector com-
mutator. The starting anode circuit of the MCM
OA4G
tube
is
interrupted when the hole in the card passes from
under the card brush. Transfer of the A relay points
shunts the main anode circuit of the MCM
OA4G tube,
lowering the potential across it greatly and causing it
to
go out. (See principle 9 in the Type 82
Circuit
Description. )
Transfer of the A relay points places the sort trigger
OA4G tube under control of the center and outer
selector commutator brushes via MCM-R2.
When
the
center brush on the selector commutator breaks after 12
time, the hold circuit for relay A
is
interrupted and the
main anode circuit of the
OA4G sort trigger tube
is
opened. Opening of the main anode circuit of the
OA4G
trigger tube causes it to go out, thus de-energizing the
sort magnet and restoring the sorting circuits to normal
by
placing the normal negative grid bias on the 2516
power tubes.
Once the sorting circuits have been restored
to
nor-
mal in the foregoing manner, any succeeding master
cards are rejected until the advent of a detail card
which
is
read
by
the rail brush.
When
a detail card
is
sensed, this card and all successive detail cards are
sorted into the 9 pocket
as
previously described, until
a master card
is
encountered.
Purpose
of
Miscellaneous Circuit
Components
The 8 mfd. capacitor across the A relay coil increases
the dropout time of this relay sufficiently to insure that
the MCM
OA4G tube will go out before anode voltage
is
again applied.
The
47,000 ohm resistor in the starter anode cir-
cuit of the MCM
OA4G limits the starter anode cur-
rent when the tube
fires.
The .001 mfd. capacitor between the starter anode
and cathode of the MCM
OA4G serves
to
bypass high
frequency transient pulses which might otherwise
fire
the tube at the wrong time.
The
.5
megohm resistor in the cathode circuit of the
MCM
OA4G connects the starting anode
to
its
cathode,
thus keeping the starter anode at its own cathode po-
tential
as
long
as
the card insulates the card brush from
the contact roll.
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