Editing Keypunch (section)

===IBM 056 Card Verifier===
[[File:Keypunching at Texas A&M2.jpg|thumb|left|Two women discussing their work while entering data onto punched cards at Texas A&M in the 1950s. The woman at the right is seated at an [[IBM 026]] keypunch machine. The woman at left is at an IBM 056 Card Verifier. Her job would be to re-enter the data and the verifier machine would check that it matched the data punched onto the cards.]]
The IBM 056 was the verifier companion to the 024 Card Punch and 026 Printing Card Punch.  The verifier was similar to the 026 keypunch except for a red error lens in the machine cover lower center.  The verifier operator entered exactly the same data as the keypunch operator and the verifier machine then [[Two pass verification|checked]] to see if the punched data matched.  Successfully verified cards had a small notch punched on the right hand edge.

The IBM 056 verifier used most of the same mechanical and electrical components as the 024/026 keypunches with the exception of the punch unit and print head.  The punch unit had sensing pins in place of the punches. The holes sensed or not sensed would trip a contact bail when the configuration was other than that entered by the verifier operator.  This stopped the forward motion of the card, and presented a red error light on the machine cover.  The notching mechanism was located in the area occupied by the print mechanism on a 026 printing keypunch.  It had a solenoid which drove the notching mechanism, and another that selected the top notch punch or end of card punch.

When an operator keying data to be verified encountered an error, the operator was given a second and third try to re-enter the data that was supposed to be in the field.  If the third try was incorrect an error notch was put on the top of the card over the column with the error and the "OK" punch at the end of the card was not enabled. The data on the card could actually be correct, since the verifier operator was just as likely to make an error as the keypunch operator.  However, with three tries, the operator was less likely to repeatedly make the same error. Some verifier operators were able to guess the error on the card created by the previous keypunch operator, defeating the purpose of the verify procedure, and thus some machines were altered to allow only one entry and error notched on the second try.{{Clarify|date=August 2012}}

Cards with error notches were re-punched (using an 024 or 026) usually by "duplicating" up to the column in error, then entering the correct data.  The duplicating function was accomplished by feeding the card through the punch station without punching it. At the next station sensing pins read the holes present in the original card and transferred the data to the punching station and onto a blank card.  Columns with errors were corrected instead of being duplicated.  The corrected card was then verified to check the data again and be "OK notched".