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Repair kit
Paper-tape repair kit

Punched paper tape was once a popular storage medium for data. In was available in several formats, ranging from the 5-hole standard for telex, to the 8-hole version for computers during the 1970s. Whenever a paper-tape got torn, cut or otherwise damaged, the tape could easily be repaired by means of a paper-tape repair kit, also known as a puncture repair kit.

The image on the right shows a typical example of a paper-tape repair tool. The device is fairly small and easily fits in the palm of a hand. It is a high-precision Swiss-made tool that is suitable for the repair of all known paper-tape formats.

The tool consists of a base plate, a movable bar on top of it, a cutting knife at the right side and a manual punch. The manual punch is attached to the base plate by means of a short chain, so that it doesn't get lost. Both the base plate and the movable bar have a pre-drilled pattern of holes according to the ECMA-10 standard [2].
Paper-tape repair kit (closed)

The tool is part of a complete paper-tape repair kit and came with reels of pre-perforated self-adhesive tape that could be used as a patch when repairing tapes. Although paper-tape repair kits like the one shown here were once common tools, they are very hard to find these days. The device shown on this page was kindly donated by Museum Jan Corver in July 2012 [1].

Repairing a torn tape is really simple when using this device. First both ends of the tape have to be cut clean using the knife that is mounted at the right side of the tool. The bar is raised and the tape is inserted. Small support pins in the base plate will lock the tape in place. They are lined-up with the sprocket holes in the tape.

Next, the bar is lowered to keep the tape in place, and the knife is used to create a nice clean-edge cut. The two tapes are now brought together at the center of the tool in such a way that the two pre-cut sides are nicely aligned.
Applying the patch

Pre-perforated patches should now be applied to both sides of the tape, to ensure that the tape gets its former strength back. The top bar can be used to put pressure on the patches. If part of the torn tape is missing, it is possible to restore the information by inserting a blank piece of tape and using the manual punch to restore the information (see below).

Paper-tape repair kit (closed) Complete paper-tape repair kit Preparing to cut the tape The cut tape Aligning the two tapes Applying the patch Pressing the patch Repaired tape

Manual punch
A manual punch is supplied with the repair tool. It is attached to the base plate by means of a chain, so that it doesn't get lost. It can be used to clear obstructed holes, delete a character (by punching all holes), making corrections and restore information (by punching a blank tape).

Deleting a character is straightforward. The tape is placed on the base plate, with the character to be deleted aligned with the center holes. Next, the bar is lowered and the manual punch is used to punch all holes in the center column. When the bar is raised again, we see that the character is replaced by five holes, which represents the Letters-shift (LTRS) in 5-level Baudot code.

Deleting a character in 7 or 8-level paper-tape is slightly more complex. Although the 7-level ASCII standard recognizes 7 holes as a Delete-character, this is not the case for 8-level ASCII.
Deleting the character by punching all holes

Corrections are also possible by using solid tape or patches to obscure the holes in the tape, and using the manual punch to punch-in the desired pattern. This also allows common sellotape to be used for repairing a torn tape, although one has to bear in mind that some devices read the holes optically. In such cases it is better to use non-transparent (opaque) tape for the repair.

Paper-tape repair kit with knife up Portable... Top view of paper-tape repair kit Character to be deleted Deleting the character by punching all holes Deleted character (replaced by Letters-Shift) Paper-tape repair kit in operation Using a patch to repair the tape

  • Repairing tapes
  • Clearing characters
  • Restoring information
  • Cutting tapes
  • Inserting data
  • Appending date
  • Creating loop tapes
  1. Museum Jan Corver, Paper-tape repair kit - THANKS!
    Device featured on this page kindly donated by Museum Jan Corver. July 2012.

  2. ECMA, Standard EMCMA-10 for Data Interchange on Punched Tape
    2nd Edition. July 1970.
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Crypto Museum. Last changed: Friday, 20 July 2012 - 11:24 CET.
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