IBM 29 - Left-Zero Program Card and Error Reset Key

Left-Zero Program Card
• The size of the left-zero :field is determined by the program card.
• A maximum of eight columns and a minimum of three columns can he
programmed.
The size of a left-zero field is determined by the pro-
gram card coding (Figure 1-2). The first column of
the field, high order, is punched with the correct digits
to indicate field length. The remainder of the field is
defined by 4' s or 12' s for field definition.
Left-Zero Error Reset Key
• This key erases information stored in left-zero registers.
When the operator presses the error reset key, the +48
volts is removed from the left-zero circuits, and all
relays drop. The left-zero control relays will repick
when the key is released.
PROGRAM 1 PROGRAM 2
First
Remaining
First
Remaining
Field Size
Column Columns
Column
Columns
8
2
12 8
4
7
3
12 9
4
6
2-3
12
8-9
4
5
1-2
12 7-8
4
4
1-3 12 7-9
4
3
1-2-3
12 7-8-9
4
Figure 1-2. Left-Zero Program Card Coding
1-2