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E L E C T R I C A L
P R I N C I P L E S
101
As shown in Figure 97, a set of CB's (P5 and
P6) make 5 teeth after each index line and break
8 teeth after.
P17 cam contact allows only the
pulses from 9.F through 1.5 to pass.
Each time
the CB's make, rhe trigger is turned
ON
in exactly
the same manner described in the section, Coz~nter
Rmd-i~r
f
roln Card.
Observe that the 25L6 power tube is normally
conductive, since its control grid is tied to the
+ I 50 volr line. This means that its anode is nor-
mally at low potential. Also observe that the grid
of the 25L6 is coupled to the anode of tube 2 of
the trigger through coupling capacitor C?. When
the trigger goes
ON,
the anode of tube 2 drops sud-
denly from about $136 volts to +40 volts. This
negative shift in voltage is passed through C:? to
the grid of the 25L6 and momentarily cuts it off.
When rhe 25L6 stops conducting, its anode poten-
tial rises to $1 50 volts, and the resulting positive
pulse is passed to the suppressors of all the switch
tubes controlling the multiplier and multiplicand
read-in.
Another set of CB's (P7 and P8J make at
each index line and open three teeth after the line.
PI8 cam contact allows only the pulses from 9
through
O
to pass to the right side of the trigger.
Each time that P7 and P8 make from
8
to 0, the
trigger is turned
OFF
in exactly the same manner
it was turned
O N
by Pf and P6.
Consequently,
the trigger goes
ON
at mid-index points from 9.5
through 1.5 and goes
OFF
at index points from 8
through 0, thus providing 9 pulses in synchronism
with card movement through the punch for read-
in control.
The by-pass capacitors CI and C? serve the same
purpose as the by-pass capacitor C in Figure 96.
As in the case of the read-in triggers, this method
of generaring pulses eliminates all trouble due to
bouncing contacts. For example, once the trigger
is turned
ON
by PI and P6 making, it makes no
difference if they do open and close because of a
bounce.
The trigger cannot be turned
OFF
by
opening P5 and P6; it can be turned
OFF
only by
P7 and P8 closing. Likewise, once the trigger is
turned
OFF
by P7 and P8 making, any break in
rhe circuit will not turn the trigger ON; only a
circuit through P5 and P6 can turn it
ON.
The
two .0025 megohrn wire-wound resistors shown
connected from ground to P17 and PI8 are pro-
vided to maintain a sufficient flow of current
through the contact points in order to p- &event a
film forming over these points when no current
flows.
The read-in trigger and power tube are tubes
B-35 and B-36 in the B chassis.
The circuit is
shown in Section 30B of the wiring diagram. Ob-
serve that the read-in pulse control trigger is a
slow-speed trigger.
Counter Read-In at High Speed
When multiplying, high-speed pulses at the rate
of 3 5,000 per second are fed to the multiplicand
counter. For each cycle during which the multi-
plicand counter is to be "rolled," ren pulses are
fed to the counter to provide a timed carry pulse
and restoration of the counter back to its original
setting. These Ten pulses are positive pulses which
are applied to the grid of a normally cut-off in-
verter triode.
The positive pulses cause conduc-
tion through the tube, and the resulting negative
pulses are fed ro the counter through an anode re-
sistor tap.
' T he complete wiring diagram for the multipli-
cand counter read-in controls in the
D
chassis may
be seen in the circuit diagram in Sections 3 3 and
34. Posts 1, 5, 8, 12, 15, and 19 are connected to
the mulriplicand counter entry hubs on the con-
trol panel through ,the connecting cable. Posts 2
1,
26, 28, 33, 35, and 40 connect to the input of the
six multiplicand counter positions. The indicator
lights indicate which of the six read-in triggers
( D l , D4, D7, D10, D13, D16) is
ON,
that is,
which is accepring card read-in pulses.
No indi-
cation is given of the high-speed read-in.
Only one voltage divider is used t o furnish the
-50 volt potential normally applied to all pentode
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