instead of mechanical sensing pins. This made the 059 much quieter than the 056 (which was often louder than the 024 keypunch). The optical sensors used a single light source, which was distributed to various sites within the machine via fiber-optic lightpipes. Despite the technology, the basic mode of operation remained essentially the same as with the 056. Ironically, not all verifier operators appreciated the noise reduction. When used in a room also containing 029 keypunch machines, the verifier operators sometimes missed the auditory feedback provided by the loud "thunk" noise emitted by the older 056. Some were known to compensate by hitting the keys harder, sometimes actually wearing out keyboard parts. IBM 129 Card Data Recorder Introduced with the System/370 in 1971, the IBM 129 was capable of punching, verifying, and use as an auxiliary, on line, 80 column card reader/punch for some computers. A switch on the keyboard console provided the ability to toggle between the punch and verify modes. The transistorized IBM 129 Card Data Recorder's primary advantage over other IBM keypunches was that it featured an electronic 80-column buffer to hold the card image. When using earlier IBM keypunches, a keystroke error required the card to be ejected by pressing the Release and Register keys, the error corrected by pressing the Duplicate key until the error column was reached, typing the correct data for the rest of that card, then pressing the Release key and manually removing the bad card from the output card stacker before it was placed in the deck (this required some practice, but quickly became an automatic action that you no longer had to think about). With the 129, a keystroke error could be erased by pressing the Backspace key and re-keyed. The entire 80-column card was punched automatically, as fast as the mechanism could go, when the Release key was pressed. Logic was in SLT modules on a swing out, wire-wrapped backplane. A secondary advantage of the 129 was that the speed of the keying operation was not limited by punching each column at the time of the keystroke. The 129 could store six programs in its memory, selectable by a rotary switch. Unlike earlier keypunch machines, the program cards were read into memory via the regular card-feed path, and were not wrapped around a "program drum". Thanks to its use of electronic memory, the 129 did not have a separate