Tuesday, 12 August 2014

Tape formats

Data was represented by the attendance or absence of a aperture at a accurate location. Tapes originally had 5 rows of holes for data. After tapes had 6, 7 and 8 rows. An aboriginal electro-mechanical artful machine, the Automatic Sequence Controlled Calculator or Harvard Mark I, acclimated cardboard band with 24 rows.[1] A row of narrower holes that were consistently punched served to augment the tape, originally application a caster with adorable teeth alleged a sprocket wheel. After optical readers acclimated the sprocket holes to accomplish timing pulses.
Text was encoded in several ways. The ancient accepted appearance encoding was Baudot, which dates aback to the nineteenth aeon and had 5 holes. The Baudot cipher was never acclimated in teleprinters. Instead, modifications such as the Murray cipher (which added carrying acknowledgment and band feed), Western Union code, International Telegraphic Alphabet #2 (ITA 2), and American Teletypewriter cipher (USTTY), were used.[2] Added standards, such as Teletypesetter (TTS), Fieldata and Flexowriter, had 6 holes. In the aboriginal 1960s, the American Standards Association led a activity to advance a accepted cipher for abstracts processing, which became accepted as ASCII. This 7-level cipher was adopted by some teleprinter users, including AT&T (Teletype). Others, such as Telex, backward with the beforehand codes.
Tape for punching was 0.00394 inches (0.1 mm) thick. The two a lot of accepted widths were 11/16 inch (17.46 mm) for 5 bit codes, and 1 inch (25.4 mm) for tapes with six or added bits. Aperture agreement was 0.1 inch (2.54 mm) in both directions. Abstracts holes were 0.072 inches (1.83 mm) in diameter; augment holes were 0.046 inches (1.17 mm).[3] Cardboard band rolls in both widths are still commercially accessible as of 2012.[4]
Chadless Tape[edit]
Most tape-punching accessories acclimated solid punches to actualize holes in the tape. This action accordingly created "chad", or baby annular pieces of paper. Managing the auctioning of chad was an annoying and circuitous problem, as the tiny cardboard pieces had a addiction to escape and baffle with the added electromechanical locations of the teleprinter equipment.
Chadless cardboard tape
Chadless 5-level Baudot cardboard band about ~1975-1980 punched at Teletype Corp.
One aberration on the band bite was a accessory alleged a Chadless Press Reperforator. This apparatus would bite a accustomed teleprinter arresting into band and book the bulletin on it at the aforementioned time, application a press apparatus agnate to that of an accustomed page printer. The band punch, rather than punching out the accepted annular holes, would instead bite little U-shaped cuts in the paper, so that no chad would be produced; the "hole" was still abounding with a little cardboard trap-door. By not absolutely punching out the hole, the press on the cardboard remained complete and legible. This enabled operators to apprehend the band after accepting to analyze the holes, which would facilitate relaying the bulletin on to addition base in the network. Also, of course, there was no "chad box" to abandoned from time to time. A disadvantage to this apparatus was that chadless tape, already punched, did not cycle up well, because the bulging flaps of cardboard would bolt on the next band of tape, so it could not be formed up tightly. Addition disadvantage, as apparent over time, was that there was no reliable way to apprehend chadless band by optical agency active by after accelerated readers. However, the automated band readers acclimated in a lot of standard-speed accessories had no botheration with chadless tape, because it sensed the holes by agency of edgeless spring-loaded analysis pins, which calmly pushed the cardboard flaps out of the way.

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