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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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