IBM Selectric I/O Manual Of Instruction page 61

Keylever Pawl
Index Pawl
Interposer Latch
FIGURE 117. Carrier Return/Indexing Operational Control Mechanism
Operational Control Mechanism
The operati ona I control mechanism is a compact unit con-
tained in a bracket located under the operational cams. The
purpose of the mechanism is to select the function to be
operated, control the movement of the cam, and transfer
the cam motion to the selected operation. To fulfill these
three purposes, each cam requires four basic parts in its con-
trol mechanism. They are: an interposer to select the oper-
ation and to help with the cam control, a clutch release arm
to control the cam, a restoring device for the interposer, and
a cam follower to transfer the cam motion to the operations.
The principle of operation for both cam control mechanisms
is the same; however, the parts design differs slightly.
Keylever Pawl
GUide Bracket
Interposer
Cam Follower
1. Interposers
Each mechanism operated by the cams requi res an interposer
to select the mechanism to be operated and to cause the cam
to be engaged. These five interposers operate front to rear
through slots in the operational control bracket and are
latched forward on an adjustable guide attached to the front
of the bracket (Figs. 117 and 118). The interposers are each
spring loaded to the rear by an extension spring between the
interposer and the rear of the operational control bracket.
Attached to the front of each interposer is a sma II pivoting
latch. The latch is spring loaded upward against the inter-
poser so that the top portion forms a hook for the interposer.
The latch hooks under the keylever pawl guide bracket to
Operationa I Latch
FIGURE 118. Backspace/Space/Tab Operational Control Mechanism
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