Carriage control tape

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Carriage control tape on an IBM 1403 printer. No channel punches are visible in this photo.
IBM 1403 printer opened up as it would be to change paper. Note carriage control tape in upper right.

A carriage control tape was a loop of punched tape that was used to synchronize rapid vertical page movement in most IBM line printers from unit record days through the 1970s. The tape loop was as long as the length of a single page. A pin wheel moved the tape accurately using holes in the center of the tape. A hole punched in one of the other channels represented a particular position on the page. Channel one was typically used to indicate the top of the page and might be the only channel used. Another channel might indicate the summary line on an invoice, enabling rapid skipping to that line. IBM provides a special manual punch that allowed accurate placement of the channel punches. Skipping occurred under computer control, but a form feed switch on the printer control panel allowed a manual skip to the top of the page. The tapes could be easily changed when new, continuously fed forms were loaded into the printer.