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112
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
on the cycle point that the secondary timer carries.
Since the secondary timer receives advancing pulses
at 14, it also carries at 14; and consequently com-
puring will stop at 14 in the primary cycle, thus
leaving the primary timer where i t started (at 14).
Compute Start Control and Primary Timer
Referring to Section 21 of the circuit, it will be
observed that the primary timer consists of four
triggers in tandem, namely, A26, A27, A28, and
A29. The A26 trigger is normally
OFF,
while the
others are normally
ON.
The A28
OFF
side utilizes
half of A20 as a follower, while the two triode
sections of A34 are used as a follower for the
O N
and
OFF
side of A29. Followers are used to avoid
loading the triggers, as excessive loading of
a
trig-
ger results in erratic operation. Note that the in-
dicator block in position A30 is used to indicate
the status of the primary timer ar any time.
Operation of the primary timer is effected by
negative B pulses developed by a pentode switch
tube A21 (Section 23A) afrer computing is init-
iared under control of the punch unit. The grid
of the A21 switch is connected to the grid of the
ON
side of A3 1 trigger, and consequently follows
ir in potential.
Since A31 is normally
OFF,
A21
cannot conduct, thus preventing response of A21
to the A pulses applied to its suppressor.
The grid of tube I of trigger A3 1 is coupled t o
the anode resistor of tube 2 of rrigger A32, which
is also normally
OFF.
The grid of tube 2 of trigger
A32 is directly coupled to P24 cam contact through
R l B U contact in the punch unir. With a card at
the die card lever, when P24 makes at 11.1 on the
punch index, a circuit is completed from the
+
40
volt line to the grid of A3Z2, and trigger A32 is
turned
ON
to initiate computing. The manner in
which trigger A32 goes
ON
is exactly the same as
described in connection with the read-in triggers.
When A32 goes
ON,
the potential at the A322
tube drops, and a negative pulse is rransmitted to
A3 1 trigger (OFF side) from a tap on rhe load re-
sistor of A322.
A31 is thus turned ON, and the
grid of tube 2 rises t o cathode potential as does the
grid of the A21 switch.
With the grid of A21
above cutoff, A21 will respond to any pulses ap-
plied to its suppressor. The suppressor of A21 is
normally at -10 volrs, which is sufficient to block
conduction. However, the suppressor is also con-
nected by a capacitor to the anode of A16, the
source of the A pulses.
Each time the A pulse goes positive, A21 con-
ducts, and the porential at its anode drops. Hence
A21 inverts these A pulses to B pulses, which in
turn are taken from a midpoint tap on the load re-
sistor for A21 and fed to A26, the first stage trig-
ger of the primary timer. As previously explained,
the positive pulses applied to the primary rimer are
of insufficient amplitude t o affect its status; only
negative pulses will be recognized by the primary
timer triggers.
Remember from Figure 107 that the cycle points
represent negative shifts in the B pulses or positive
shifts in the A pulses. A positive shift in the B
pulses or negative shift in the A pulses occurs at
half time, that is, 1.1, 2.1, etc.
The first positive A pulse applied to A21 after
computing is initiated, produces a negative B pulse
to advance the primary timer to 11 by turning A26
ON, as indicated in Figure 107. Since A27, A28,
and A29 are already
O N
when computing starts,
all triggers will be
ON
after the first B pulse. The
second B pulse developed by A21 turns A26
OFF,
and the potential at the A261 anode drops, pro-
ducing a negative pulse.
This negative pulse is
taken from the midpoint of the load resistor for
A261 and passes to A27 trigger, turning A27
OFF.
As A27 turns OFF, its tube I develops a negative
pulse which is applied ro the third-stage trigger,
A28, turning it
OFF.
Follower tube A20 starts con-
ducting and a negative pulse appears at the anode
of A20, which is passed on to A29 to turn it
OFF.
Therefore, after two B pulses are applied t o the
primary timer, all triggers are
OFF
and the timer
is at 0.
The next negative pulse applied to A26 trips it
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