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Distinguishing Classes of Data Using a Single Timing Channel

IP.com Disclosure Number: IPCOM000094992D
Original Publication Date: 1965-Aug-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 2 page(s) / 25K

Publishing Venue

IBM

Related People

Grant, CH: AUTHOR [+4]

Abstract

Sensing of timing channel marks having controlled spacings permits distinguishing between different classes of data to be sampled on a recording medium. The medium can be magnetic tapes, disks, drums, paper tape, cards or the like. Classes of data can include various possible combinations such as mixtures of mark data, punched holes or divergent codes. For illustrative purposes only, the following refers to the reading of cards having intermixed punched and marked fields with a single edge marked time channel.

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Distinguishing Classes of Data Using a Single Timing Channel

Sensing of timing channel marks having controlled spacings permits distinguishing between different classes of data to be sampled on a recording medium. The medium can be magnetic tapes, disks, drums, paper tape, cards or the like. Classes of data can include various possible combinations such as mixtures of mark data, punched holes or divergent codes. For illustrative purposes only, the following refers to the reading of cards having intermixed punched and marked fields with a single edge marked time channel.

A constant speed card feeder moves card 10 past a sensing station which utilizes both direct and reflected illumination to energize a series of photodetectors. Direct illumination detects passage of leading edge 11. The initial mark for first field 14, a punched field, occurs distance 12 from 11. If the first field had been a marked field, distance 12 would preferably have been greater than for the punched field, a double distance simplifying circuit design. When the first mark of 14 is sensed, a column of data is sampled by the punched data sensor. Timing marks for field 14 recur at standard distance 15 and each cause a column of punched data to be sampled.

To indicate marked field 16 follows punched field 14, a gap is left in the timing channel following 14 which, when sensed, causes the machine to switch to mark mode. Thus, when the first timing pulse of mark field 16 is sensed, the sensor is l...