Carriage control tape
| Industry | Computer hardware |
|---|---|
| Founded | June 16, 1911 in Endicott, New York, United States |
| Products | Printers, punched tape devices |
A carriage control tape consisted of a continuous loop of punched tape designed to coordinate swift vertical paper movement in the majority of IBM and various other line printer models throughout the unit record period up until the 1960s. This tape loop was cut to correspond exactly with the length of one page and was advanced with precision by a pin wheel mechanism that engaged holes located in its central area. Specific page positions were identified by holes punched into distinct channels—commonly, channel one signified the top of the page and was often the sole channel utilized. Additional channels could designate particular lines, such as invoice totals, facilitating rapid skipping through the document. IBM supplied a manual punching device to ensure accurate placement of these channels. The computer controlled the skipping function, while a manual form feed switch allowed for top-of-page skips. Operators could easily replace tapes when loading new continuous forms.
Forms control buffer
With the introduction of the IBM 3211, printers transitioned to using a "forms control buffer" (FCB), which served as an electronic substitute for the traditional carriage control tape. Print tasks could specify particular FCBs that were automatically loaded prior to printing, thereby minimizing the need for operator intervention.
Conventions
Typically, channel 1 marks the first printable line on a form and triggers a "skip to channel 1" command that accelerates page positioning more effectively than line-by-line spacing. Channel 9 is positioned slightly above the bottom of the page, creating space for footers or total amounts during printing. Channel 12 denotes the final printable line on the page. These channel assignments are not fixed and can be modified according to specific application requirements.
Sources
- IBM 407 manual p.129 ff
- Excerpt on printing from IBM 1130 manual
- Rack for holding carriage tapes at Computer History Museum