IBM Selectric I/O Manual Of Instruction page 21

Selector Compensator Tube
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Compensator : .
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Ball
A. INTERPOSER AT REST B. INTERPOSER LATCHED
DOWN
FIGURE 37. Interposer Latch and Selector Compensator
An interposer must be latched down to insure that it wi II remain
in the path of the fi Iter shaft blade unti I the cycle operation
occurs. Unless latched down, the interposer could restore up-
ward without being driven forward. This would result in an
erroneous character because of no character selection (+ 5
rotate ti It 3).
With this latching device, one interposer can be latched down
just as the previously depressed interposer is being operated
forward. The second interposer wi II then be operated forward
as soon as the cycle operation for the first interposer is com-
pleted. This is known as character storage and tends to even
erratic typing rhythm.
Selector Compensator
The selector compensator prevents simultaneous depression of
two keylevers insuring that only one interposer at a time can
be operated down and then forward. If more than one inter-
poser at a time were depressed, they would be operated for-
ward together and a selection error would result causing the
wrong character to print. A hook shaped lug at the rear of
each interposer operates in a device called the selector com-
pensator attached to the rear interposer guide comb (Fig. 37).
The compensator contains closely spaced steel balls that pre-
vent downward movement of two or more interposers simulta-
neously (Fig. 380). When an interposer is down, the steel
balls shift in the tube of the compensator to block the down-
ward movement of any other interposer (Fig. 38b).
Selector Compensator Ball
00
A. Simultaneous Keylever Depression Blocked
B. Second Keylever Depression Blocked
FIGURE 38. Selector Compensator Action
14
The hook portion of the interposer lugs extends to the rear just
to the center I ine of the steel balls (Fig. 37). When an inter-
poser is driven forward after being depressed at the rear, the
lug will not be between the steel balls and another interposer
can be depressed. With this arrangement, the operator does
not have to wait unti I an interposer is restored upward before
actuating another.
An adjustable stop at each end of the compensator tube keeps
the balls somewhat centered between the interposers. The balls
are thus prevented from shi"fting too for left or right. If the
balls were allowed to move too far under the interposer lugs,
they would partially block the depression of an interposer and
the keyboard touch would suffer. The stops are removable so
that the steel balls may be removed and cleaned if necessary.
Selector Bails and Links
Seven se lector bai Is are mounted between the si de frames so
they can operate forward and back (Fig. 35). Each bai I is in
front of a selector lug position on the interposers. When an
interposer containing all its lugs is driven forward, all the
selector bai Is are moved forward. If any lug is absent from
an interposer, the bai I for that position wi II not be operated
forward by that interposer.
Seven sliding interposers called the latch interposers are lo-
cated under the left end of the se lector bai Is (Fig. 35). These
interposers operate
Each latch interposer has a lug that extends up directly in front
of a selector bai I. As the selector bai I is moved forward, the
latch interposer is moved forward by the bai I. The bai Is and
latch interposers are paired so that each bail operates only one
interposer. An extension spring at the bottom of each latch
interposer loads the interposer and its selector bail to the rear.
The latch interposers rest against ac'justable lugs at the rear to
prevent the bai Is from being forced against the selector inter-
poser lugs. This prevents the selector interposers from binding
against the bailsas the interposers are depressed. The stop lugs
also help prevent the selector bails from bouncing as they are
restored to the rear.
An adjustable I ink connects each latch interposer to one of the
selector latches of the differential mechanism (Fig. 35). When
a latch interposer ismoved forward, the selector latch connected
to that interposer is pulled forward to prevent its be ing operated
downward by the latch bai I.
Cycle Clutch Latch
Although not actually a part of the keyboard section, the cycle
clutch latch is directly related to the keyboard mechanisms.
It is through depression of a keylever that the cycle clutch is
allowed to operate.
The cycle clutch latch pivots on a bracket at the front of the
power frame. It pivots from the top and rests in a vertical po-
sition just in front of the cycle clutch sleeve. A thin metal
plate, mounted in rubber on the rear of the latch prevents rota-
tion of the sleeve thereby preventing the cycle clutch spring
from tightening on the cycle clutch pulley hub (Fig. 39). The
latch is held in this position by the cycle clutch latch pawl and
I ink assembly that extends forward from the latch. The cycle
cl utch latch pawl pivots on the I ink. An extension spring be-
tween the two parts rotates the front of the pawl up into a latched