Margin Control - IBM Selectric I/O Manual Of Instruction

Tab Lever Cannot Latch
Although Operated To The Rear
Escapement Torque Bar
FIGURE 174. Carrier Return Tab Interlock
Tab Contacts
Tab operation may operate three kinds of contacts. These are
C-5 (feedback contact), a latch type contact (transmitting
contact) which identifies the operation and a tab interlock
contact. The first two (C-5, transmitting) were covered under
"Operational Selection Unit". The third is a tab-interlock
contact that stays made to interlock the machine through the
whole tab operation.
Tab-Interlock Contact (Early)
The tab-interlock contact is a mi croswitch (Fig. 175). It is
mounted inside the left side of the power frame by a bracket.
The tab on the left end of the torque bar operates the inter-
lock .. contact (Fig. 175).
FIGURE 175. Tab-Interlock Contact (Early)
With the torque bar latched, the tab rises allowing the con-
tact to operate under its own spring tension. When the torque
bar restores, the tab lowers opening the contact.
69
Tab Interlock Contact (Late)
The tab interlock contact is a snap action switch. It is
mounted in the same place as the old style interlock. The
main difference is the manner in which the contact is trans-
ferred.
As the tab torque bar is rotated the tab arm (Fig. 176) moves
upward pulling upward on the trigger lever. Since the torque
bar rotates through an arc the trigger lever wi II cam off the
tab arm. However, the trigger wi II be in contact with the
rear si de of the tab arm and wi II be cammed toward the rear
as the torque bar continues to rotate.
Trigger lever
Actuating Lever
----...J.IIMt
FIGURE 176. Tab Interlock (Late)
The motion from the trigger is transferred through the actuat-
ing lever (Fig. 176) to the interlock contact transferring the
contact. When the tab lever is unlatched the torque bar re-
stores. As the torque bar restores the trigger lever resets over
the tab arm and allows the contact to re-transfer.
The new interlock is considered positive action. Either up-
ward or rearward motion applied to the trigger lever will
transfer the contact.
MARGIN CONTROL
The term "margin" denotes the distance between the edge of
the paper and the typewritten material. The left and right
margins are determined by the position of the margin stops on
the margin rack. The carrier travel is restricted by contact-
ing the margin stops.