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E L E C T R I C A L P R I N C I P L E S
133
as followers for trigger MY, the first stage of the
tertiary timer.
M3, the second stage of the ter-
tiary timer, uses the two sections of M4 as follow-
ers, while the rwo sections of MI serve as followers
for the third stage trigger M2. The trigger stages
are mounted in reverse order to simplify wiring.
The triggers M2, M3 and M5 are slow-speed
triggers because the frequency of pulses to these
triggers is quite low even when computing at
35,000 kc frequency of the multivibrator.
The
slow-speed trigger gives more stable operation at
the frequency at which the tertiary timer operates.
Observe rhat each trigger in the tertiary timer
has two followers, one for the
O N
side and one for
the
OFF
side. This is done to prevent loading the
triggers.
Each follower has a voltage divider be-
tween its anode and the -100 volt line. The mid-
point of these voltage dividers is ar -25 volts as
long as the corresponding follower is conducting,
and at +25 volts as long as rhe corresponding fol-
lower is non-conducting
The midpoint of each
voltage divider is connected to the associated grids
of the interpolating tubes.
By this means, the
interpolating tubes determine which trigger (or
triggers) in the tertiary timer is
ON
and thereby
establish the column shift position.
The tertiary timer is cancelled to 1, so as to
indicate the column shift cycle in which the ma-
chine is operating. Since the tertiary timer oper-
ates as a binary counter, the followinn conditions
-
will exist during successive column shift cycles:
ON
-
OFF
-
CODE
1st column shift
M5
M2, M3
1
2nd column shift
M3
M5, M2
2
3rd column shift
M5, M3
M2
1, 2
4th
column shift
M2
MS. M3
4
5th column shift
M5, M Z
M3
1,
4
6th column shift
M3, M2
M5
2,
4
The followers for the triggers will follow their
respective tubes; the conditions existing at the
midpoints of the voltage dividers connected to the
followers is as follows:
M-6
M-61 M-4b
M-41
M-I
M-11
(M-j
(W5
(M-3
(M-3
(M-;
(M-z
ON) OFF)
ON)
OFF)
ON)
OFF)
1st column shift
- + + -
+ -
2nd column shift
+ - -
-
+ + -
3rd column shift
+ - + + -
4th
column shift
+
-
+ - -
5th column shift
-
f
+
-
-
+ +
6th column shift
f
-
-
+
-
+
The triode sections M211 through M161 (Sec-
tion 52 of wiring diagram) signal the column shift
cycle in which the machine is operating.
M211
conducts during the first column shift cycle, M201.
during the second, M191 during the third, etc.
Observe that the grids of triodes M211 through
M161 are each connected to a voltage divider be-
tween the -100 volt line and the anodes of the three.
corresponding interpolating tubes.
M211 for ex-
ample, can conduct only if M141, M142, and M2
1 2
are all cut off. MI42 is controlled by M62; MI41
is controlled by M41; M212 is controlled by M11.
By examining the table in the preceding paragraph.
it will be seen that all three of the interpolating
tubes controlling M211 are cut off during the first
column shift cycle; hence, M2 1 conducts during
the first column shift cycle.
By examining the
above table and observing the grid connections of
the other interpolating tubes, it will be found thar
M201 conducts during the second column shift
cycle, MI91 during the third column shift, MI81
during the fourth, erc.
The table below shows the tubes conducting
during the successive column shift cycles:
Column
Tertiary
Shift
Timer
Followers
Interpolating Tubes
Control-
--
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