Editing IBM 1401 (section)

===Modifiers for Select Stacker (K) instruction===
The Select Stacker (K) instruction sent commands to various devices. It was named for its relevance to the 1402 reader/punch.

{| class="wikitable"
|-
! [[Binary-coded decimal#IBM and BCD|BCD]] Character
! Unit
! Meaning
|-
| align="center" | Blank
| 1401
| set program activity recording at BBB only if A is, dd
|-
| align="center" | 1
| 1402
| select last card read to stacker 1 if within 10 ms
|-
| align="center" | 2
| 1402
| select last card read to stacker 8/2 if within 10 ms
|-
| align="center" | 4
| 1402
| select previous card punched to stacker 4
|-
| align="center" | 8
| 1402
| select previous card punched to stacker 8/2
|-
| align="center" | = or #
| 1444
| select previous card punched to stacker 2
|-
| align="center" | L
| 1009
| operate in load mode
|-
| align="center" | $
| 1402
| overlap on
|-
| align="center" | A
| 1009
| suppress 3-second alarm
|-
| align="center" | C
| DDC
| read request
|-
| align="center" | D
| 1009
| set direction to receive
|-
| &nbsp;
| DDC
| write request
|-
| align="center" | E
| 1009
| set direction to transmit
|-
| &nbsp;
| DDC
| reset
|-
| align="center" | F
| 1009
| send EOF
|-
| align="center" | .
| 1402
| overlap off
|-
| align="center" | )
| 1402
| reset overlap
|-
|}
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