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Browse Prior Art Database

Process for Measuring Magnetic Tape Velocity

IP.com Disclosure Number: IPCOM000090688D
Original Publication Date: 1969-Jun-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 21K

Publishing Venue

IBM

Related People

Breitenbach, RC: AUTHOR

Abstract

The velocity of magnetic tape movement is computed by recording a special pattern of a known length using a multiplicity of fixed length IBG's and short data records, incrementing a counter as the special pattern is read, and computing the velocity from the counting time and known pattern length. Some magnetic tape drives include apparatus for interspersing IBG's between data records with accurate and reliable IBG lengths. This method makes extensive use of these accurate IBG lengths in a special data pattern, which includes a series of short 1-byte data records. Tape marks are defined as recordings of 0's in selected tracks on magnetic tape, with the remainder of the tracks being blank, and are typically 40 bytes long.

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Process for Measuring Magnetic Tape Velocity

The velocity of magnetic tape movement is computed by recording a special pattern of a known length using a multiplicity of fixed length IBG's and short data records, incrementing a counter as the special pattern is read, and computing the velocity from the counting time and known pattern length. Some magnetic tape drives include apparatus for interspersing IBG's between data records with accurate and reliable IBG lengths. This method makes extensive use of these accurate IBG lengths in a special data pattern, which includes a series of short 1- byte data records. Tape marks are defined as recordings of 0's in selected tracks on magnetic tape, with the remainder of the tracks being blank, and are typically 40 bytes long. Also, diagnostic mode is an operation in which recording hardware reacts to any attempt to write consecutive 1's by recording a blank or dead track instead. This dead-track recording can be performed selectively for any track, any combination of tracks, or all tracks.

The pattern is recorded by placing a normal tape mark 10 at the beginning of the record, which is then followed by IBG 11. A 1-byte record 12 is then recorded, including a preamble, an all 1's marker, the 1-data byte, another all 1's marker, and a postamble. Record 12 is followed by a series of IBG's 13, 15, 17, 19, and 21 which are interspersed between other similar 1-byte records 14, 16, 18, and 20. The pattern is completed with a special record 22 which includes a normal preamble and marker 2...