ISO/IEC 8441-2:1991
(Main)Information technology — High density digital recording (HDDR) — Part 2: Guide for interchange practice
Information technology — High density digital recording (HDDR) — Part 2: Guide for interchange practice
Specifies the minimum performance levels necessary for the effective interchange of information using HDDR. Describes test methods for these levels. Includes terms and definitions. Annexes A and B are for information only.
Technologies de l'information — Enregistrement numérique à haute densité (HDDR) — Partie 2: Guide pour l'échange d'information
General Information
Standards Content (Sample)
ISOAEC
INTERNATIONAL
STANDARD
First edition
1991-08-01
Information technology - High density digital
recording (HDDR) -
Part 2:
Guide for interchange practice
Technologies de I ’informa fion --- Enregistrement nun&-ique Zl harrte
densife (HDUR) -
Partie 2: Guide pour I ’echange d ’informafion
--~ ~--
-- -_~ -._- -----_
--- -_.__ .---
-__ -~ - --
Reference number
ISO/IEC 8441-2:1991(E)
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ISOAEC 8441=2:1991(E)
Contents
Page
1 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .v. . 1
2 Normative references . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
...................... 1
3 Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
4 Recording and reproducing characteristics . . .
. . . . . . . . . . . . . . . . . . . . . . . . .*. 4
General
4.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ._. 4
4.2 Tape Speeds
. . . . . . . . . . . .I. 4
4.3 Track configurations . .
.................... 5
4.4 RecordeVreproducer characteristics .
. . 5
4.5 Other characteristics . 6
....................
5 Methods for high density digital recording . . 15
5.1 Introduction ._._.,. 15
5.2 Record transfer function . .
............. 15
5.3 Flux transition densities and rates for high density recording 15
5.4 Data input/output .-.-.-.-.-. 16
5.5 Data sense . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .-. 16
5.6 Reproduce equalization . . . . . . . . . . . . . . . . . . . . . . . . . . . . .~.
16
5.7 Other System Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
0 ISO/IEC 1991
All rights reserved. No part of this publication may be reproduced or utilized in any form
or by any means, electronie or mechanical, including photocopying and microfilm, without
Permission in writing from the publisher.
ISO/IEC Copyright Office l Case Postale 56 l CH-1211 Genhve 20 l Switzerland
Printed in Switzerland
ii
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ISO/IEC 84452:1991 (E)
5.8 Auxiliary data recording . . . . . . . . . . . . . . . . . . . . . . . _ . . . . . . . . . . . . . . . ._._. 17
Annexes
A Operating modes, Performance categories, and Cross-play criteria
for high density PCM recordinq Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
.
A.l Performance categories . . 18
AI1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
A.1.2 Record head gap length for category A and category B
Performance . . . . . . . . . . . . . ._.-.-.-.-. 18
A.1.3 Record head gap lenqth for category C Performance . . . . . . . . 18
\
A.1.4 Operating modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
A.2 Single track serial high density recording . 19
A.2.1 Serial high density recording with wideband analogue
recorder/reproducer (category A) . 19
.................................. 21
A.2.2 Parallel high density digital recording
B Recording techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ._. 22
B.l Recording code names and their abbreviations . 22
8.2 Enhanced NRZ format for parallel HDDR . 22
22
B.2.1 ENRZ coding .
B.2.2 ENRZ - parallel HDDR format . 22
...................................... 22
B.2.3 Summary of enhanced NRZ format
B.3 Miller squared format (M*) for parallel HDDR . . . . . . . . . . . . . . . . . . . . . . . 23
B.3.1 Miller squared coding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
B.3.2 M* format for parallel HDDR . . . . 23
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
B.3.3 Summary of M* formst
B.3.4 M* format bandwidth utilization/packing density . 24
B.4 Randomized NRZ-L format parallel HDDR . 24
8.4.1 RNRZ-L coding . . 24
B.4.2 RNRZ-L parallel HDDR format . . . ._._. 24
8.4.3 Summary of randomized NRZ-L format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
B.4.4 Randomized NRZ-L format bandwidth utilization/packing
density . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
8.5 PROP format for parallel HDDR (Pseudo random odd parity) 26
B.5.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*.m.
26
. . .
Ill
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ISO/IEC 8441-2:1991 (E)
27
B.5.2 Summary of PROP format .
....................................... 27
8.5.3 PROP format bandwidth utilization
B.6 3PM formats for parallel HDDR . 27
27
B.6.1 General .
28
8.6.2 3PM format Versions .
Error detection and correction (formats A and B) . 29
B.6.3
....................................... 29
8.6.4 Summaty of 3PM formats A and B
3PM format bandwidth utilization . 30
B.6.5
B.7 MODAS airborne recording format . 30
B.7.1 General . . . ‘.- . 30
B.7.2 Description . . . 30
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ISOAEC 8441-2:1991 (E)
Foreword
ISO (the International Organization for Standardization) and IEC (the
International Electrotechnical Commission) form the specialized systern
for worldwide standardization. National bodies that are members of ISO
or IEC participate in the development of International Standards th ‘rough
technical committees established by the respective organization to deal
with particular fields of technical activity. ISO and IEC technical com-
mittees collaborate in fields of mutual interest. Other international or-
ganizations, governmenfal and non-governmental, in liaison with ISO
and IEC, also take patt in the work.
In the field of information technology, ISO and IEC have established a
joint technical committee, ISO/IEC JTC 1. Draft International Standards
adopted by the joint technical committee are circulated to national bod-
ies for voting. Publication as an International Standard requires ap-
proval by at least 75 % of the national bodies casting a vote.
International Standard ISO/IEC 8441-2 was prepared by Joint Technical
Committee ISO/IEC JTC 1, Information technology.
ISO/IEC 8441 consists of the following Parts, under the general title In-
formation technology - High density digital recording (HDDR):
- Part 1: Unrecorded magnetic tape for (MUX?) applications
- Part 2: Guide for interchanqe practice
L
Annexes A and B of this par-t of ISO/IEC 8441 are for information only.
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INTERNATIONAL STANDARD ISO/IEC 844%2:199l(E)
Information technology - High density digital recording
(HDDR) -
Part 2:
Guide for interchange practice
ISO/IEC TR 6371:1989, Information processing --
1 Scope
Interchange practices and test methods for unre-
corded instrcrmentation magnetic tape-
This part of ISO/IEC 8441 specifies the minimum
Performance levels necessary for the effective
interchange of information using High Density Digital
Recording (HDDR). lt also describes methods of
3 Definitions
testing for determining these levels. lt gives guid-
ante on recorders/reproducer characteristics,
For the purposes of this part of ISO/IEC 8441, the
modes of recording, and modulation Patterns.
following definitions apply.
The imperial dimensions given in this part of
ISO/IEC 8441 are the reference dimensions. The
3.1 aliasing: The false lower frequency components
metric and imperial dimensions are, however, given
resulting from an insufficient satnpling rate (i.e. less
to a sufficient degree of accuracy as to be totally
than required by the sampling theorem) when re-
interchangeable.
constructing an analogue Signal from its sampled
data representation.
3.2 baseline restorer: A device to restore the d.c.
2 Normative references -
component removed by the record/reproduce pro-
cess.
The following Standards contain provisions which,
through reference in this text, constitute provisions
3.3 bit error: The incorrect interpretation of a bi-
of this part of ISO/IEC 8441. At the time of publica-
nary bit by a message processing unit.
tion, the editions indicated were valid. All Standards
are subject to revision, and Parties to agreements
3.4 bit error rate (BER): The rate at which bit errors
based on this part of ISO/IEC 8441 are encouraged
occur in a message processing unit, expressed in
to investigate the possibility of applying the most
terms of the number of bit errors divided by the total
recent editions of the Standards indicated below.
number of bits processed in a given period of time,
Members of IEC and ISO maintain registers of cur-
or from a given length of tape.
rently valid International Standards.
3.5 bit packing density: The number of bits re-
ISO/IEC 3788: 1990, Information processing - 9-track,
corded per unit track length, usually expressed in
12,7 mm (0,5 in) wide magnetic tape for information
terms of bits per millimetre (bit/mm) or kilobits per
inferchange using Phase encoding at 126 ftpmm (3
inch (kbit/in).
200 ftpi), 63 cpmm (1 600 cpi).
ISO 6068: 1985, Information processing -- Recording 3.6 bit Slip: The condition in a message processing
characteristics of instrumentation magnetic tape (in- unit where the bit rate clock has gained (or lost)
cluding felemefry Systems) -- Interchange require- more than 180° phasing with respect to synchronism
ments. with the binary message bits.
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ISOAEC 8441-2:1991(E)
NOTE 5
When recording, this is equal to the head
3.7 bit synchronizer: An information processing
spacing, but on reproducing it is equal to head spacing
unit intended to extract the binary message and as-
only when the record and reproduce tensions and head
sociated bit rate clock included in a pulse code
spacing are equal.
modulation (PCM) Signal.
3.15 decoder: Information recovery device that ac-
3.8 Cross play: The ability to record and reproduce
cepts digital Signals from the tape reproducer and
on the Same or a different machine, or record at one
converts them into a form suitable for the output
Speed and reproduce at the Same or different Speed.
interface.
3.9
Cross talk: Interference Signals that are coupled
3.16 digital recording Code: The on-tape digital
from adjacent channels into a given processing unit
coding of the recorded binary message.
channel, usually expressed in terms of decibels
down from full scale amplitude of the unit channel.
3.17 dropout: Reduction in the reproduce Signal
amplitude severe enough to Cause bit errors.
3.10 data azimuth: The instantaneous angle in the
plane of the tape between a line perpendicular to
3.18 duty factor (of a pulse): The ratio of pulse du-
the reference edge and either of the two parallel
ration to pulse period, often expressed as a per-
lines defining data scatter.
centage.
NOTE 1 Data azimuth may be expressed as the sum of
static and dynamic components in the form 3.19 edge margin (AY): The distance between the
outside edge of the highest numbered track and the
A + nf(t)
tape edge (see figure3).
t
3.20 edge margin, minimum (d&,,): The minimum
&)dt = 0
value of the edge margin.
s
0
NOTE 6 This value places an additional constraint on
3.11 data azimuth (dynamic): The maximum angu- track configurations since, in general, the simultaneous
lar deviation, over a period of time, of the data application of all worst-case tolerantes for track width,
track location, and tape width will result in a value of edge
azimuth from its mean value as defined by data
margin less than M,.
azimuth (static). For the purpose of this definition,
the word “maximum” is interpreted as being at the
95 % probability level. For a Gaussian distribution, 3.21 encoder: A processing device that accepts a
this is two Standard deviations (20). data stream at its input and converts it to appropri-
ate digital Signals to be recorded on tape.
NOTE 2 Data azimuth (dynamic) is the maximum value
of the quantity R/(t) in 3.10.
3.22 error detection: The process of detecting bit
errors.
3.12 data azimuth (static): The mean value, over a
period of tirne, of the data azimuth.
3.23 error correction: The process of correcting
detected bit errors.
NOTE 3 Data azimuth (static) is the quantity R in 3.10.
3.24 eye Pattern: The Pattern as displayed on an
3.13 data scatter: The minimum distance between
oscilloscope, that results from the superpositioning
two parallel lines, in the plane of the tape, enclosing
of the waveforms of the different Symbols in a digital
all data transitions recorded simultaneously on all
data sequence. lt is used for assessing the quality
tracks in the Same head.
of the replayed digital Signal.
NOTE 4 The errors in location and angular relation
3.25 flaw: An imperiection in the tape Oxide coating
among transient data recorded simultaneously on all odd
or even tracks are defined by the terms: data azimuth, due to Oxide or slitting debris, foreign particulate
data scatter, and individual track data azimuth differente.
matter, absence of coating, etc.
These are approximately equivalent to the terms: head
azimuth, gap scatter, and head Segment gap azimuth dif-
NOTE 7 Such imperfections are the major Source of
ference; however, guiding misalignment is included in the
dropouts. Other imperfections such as failure to maintain
data location error definition.
slitting tolerantes and other physical nonuniformi ties tan
Cause poor tracking which results in reproduce Signal
fluctuations similar to dropouts.
3.14 data spacing: The distance on the tape be-
tween simultaneous events recorded on odd and
3.26 flutter: Tape Speed errors at frequencies
even numbered tracks when interlaced heads are
used. above 0,5 Hz.
2
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ISO/IEC 8441=2:1991(E)
3.40 head spacing (S): The distance along the tape
3.27 flux transition: A 180” Change in the flux pat-
tern in a magnetic medium, brought about by the path between the gap centrelines of head 1 and
reversal of the magnetic poles within the medium. head 2, when interlaced heads are used (see
figure 2).
3.28 flux transition density: The number of flux
3.41 head tilt: The angle between the plane tangeritt
transitions (i.e. flux reversals) per unit track length.
to the front (active) surface of the head at the
centreline of the head Segment gaps, and a line
3.29 frame synchronizer: A processing device to
perpendicular to the head reference plane (see fig-
detect and synchronize frames and subframes of a
ure 1).
pulse code modulation bit stream.
3.42 high density digital recording (HDDR): Re-
3.30 gap length: Distance from the leading edge to
cording of digital data on a magnetic medium, hav-
the trailing edge of head gap measured perpen-
ing a flux transition density in excess of 590
dicular to the track width (see figure 1).
transitions per rnillimetre (15 000 transitions per
inch) per track.
3.31 gap scatter: The minimum distance between
two parallel lines, in the plane of the tape, between
3.43 individual track data azimuth differente: The
which all the gap trailing edges of a record head are
angular deviation of the data azimuth of individual
embraced (see figure 1).
odd or even recorded tracks from the data azimuth
of other odd or even tracks.
3.32 head: A group of individual head Segments in
a fixed assembly.
NOTE 10 The difficulty in making direct Optical angular
mea?urements requires this error to be expressed as a
loss of Signal amplitude when the tape is reproduced with
3.33 head azimuth: The angle formed in the plane
an ideal head, whose gap is aligned to coincide with the
of the tape, between a line passing through the gap
data azimuth of all odd or even tracks, as compared to the
centres of the two outside head Segments and a line
maximum Signal amplitude obtainable by optimizing the
perpendicular to the head reference plane (see fig-
reproduce head azimuth for the individual tracks (see fig-
ure 1).
ure 1).
3.34 head 1: The first record or reproduce head
3.44 in-line heads: An arrangement in which all re-
over which an element of tape Passes when moving
cord or all reproduce gaps are in line on a Single
in the normal operating direction (see also 3.39).
head Stack.
3.35 head reference plane: A plane, which may be 3.45 interlaced heads: An arrangement whereby
imaginary, that is parallel to the reference edge of pairs of head Stacks are rnounted so that alternste
the tape and perpendicular to the -plane of the tape. tracks are contained in separate head Stacks of a
pair (see figure 2).
definition the tape is
NOTE 8 For the pu r-pose of this
considered as perfett (See figure 1).
3.46 jitter amplitude: The Variation in the timing of
one clock transition relative to that of the preceding
3.36 head Segment: A Single transducer that re- transition, expressed as a percentage of the mean
Cords or reproduces one track (see figure 1). interval between the clock transitions.
3.47 jitter rate: The rate of Change of the jitter am-
3.37 head Segment gap azimuth: The angle, formed
plitude expressed in hertz.
in the plane of the tape, between a line perpendicu-
lar to the head reference plane and a line parallel
to the trailing edge of the gap in a record head seg- 3.48 overbias: When the bias current is continu-
ment (see figure 1). ol~sly increased frorn an initial low level while re-
cording a relatively long wavelength Signal on tape,
the reproduce output first increases with increasing
3.38 head Segment gap azimuth differente: The
bias until it reaches a maximum, after which further
angular deviation of the azimuth of a head Segment
increases in bias Cause a reduction in output. A
gap from the head azimuth.
typical bias adjustrnent procedure involves finding
the level corresponding to maximum (or peak) out-
3.39 head Segment number: The number of the
put and then increasing the bias to Cause a specified
head Segment corresponding to the track number
reduction in reproduce amplitude where the amount
on the magnetic tape on which that head Segment
of this reduction, usually expressed in decibels, is
normally operates (see figure 2).
known as the amount of overbias.
NOTE 9 Head 1 of a pair contains all odd-numbered
3.49 overhead bits: Bits added to the bit stream to
Segments, while head 2 contains all even-numbered seg-
ments (see figure 1 and figure 2). facilitate the transmission and recovery of the bit
3
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ISO/IEC 844192:1991 (E)
stream (e.g. frame synchronization words, check 3.64 tape tensile forte: The tensile forte applied to
bits). the tape during Operation.
NOTE 12
The value of this tensile forte is not necess-
3.50 parallel HDDR: The recording of multiple PCM
arily equal to the reference tensile forte.
data streams that are synchronous to a common
clock on multitrack recorders/reproducers so that
3.65 track location (11,): The distance from the
synchronization tan be restored at playback.
centreline of the reference track to the centreline of
the recorded track location, (n) (see figure 3).
3.51 pseudorandom sequences/patterns: Repeating
sequences exhibiting many of the statistical proper-
3.66 track numbering: The consecutive numbering
ties of uniformly distributed random number se-
of tracks, starting with track 1, from top to bottom,
quences.
when viewing the magnetic surface on the tape with
the earlier Portion of the recorded Signal to the ob-
3.52 pulse code modulation (PCM): A modulation
server ’s right (see figure 3).
method in which information to be recorded is en-
coded into digital Symbols (see 3.21 and figure A-1).
3.67 track spacing (I>): The centre-to-centre dis-
tance between adjacent recorded tracks (see
3.53 reference edge: The edge of the tape nearest
figure 3).
to track 1 (see figure3).
3.68 track width (IV): The mechanical width of the
3.54 reference track location (G): Location of the
common interface of the record head Segment at the
centreline of track 1 relative to the reference edge
gaps (see figure 1).
of the tape (see figure 3).
NOTE 13 This does not include the effects of fringing
3.55 signal-to-noise ratio (SNR): The ratio of Signal
fields which will tend to increase the recorded track width
power to noise power, expressed in decibels.
by a small amount (see figure 1 and figure 3).
Single track serial HDDR: The recording of one
3.56
or more digital data streams on to a Single recording
4 Recording and reproducing
track.
characteristics
3.57 synchronization word: A fixed Pattern of bits
inserted in a digital bit stream to synchronize the
4.1 General
frame synchronizer.
This clause defines those tape and recorderire-
Having the Same rate and
3.58 synchronous:
Producer characteristics required to ensure suc-
Phase.
cessful interchange, so that tapes recorded on one
machine at one facility may be successfully reprod-
3.59 tape skew: Motion of tape such that the tape
uced on another machine of like design at another
tracks are not perpendicular to the gap centre fine.
facility. Test procedures for magnetic tape
Skew tan have both static and dynamic components
recording/reproducing equipment are given in
(see 3.10, 3.11 and 3.12).
ISO 6068:1985, annex A.
The physical properties of the tape at-e specified in
3.60 tape Speed, actual (v&: The tape speed dur-
ISO/IEC 8441-1.
ing recording and reproducing.
In general, the actual tape Speed will not be
NOTE 11
4.2 Tape Speeds
equal to t -he nominal tape Speed (see 4 -2.1).
3.61 tape Speed, effective (IJ,,,): The tape Speed 4.2.1 Tape Speed
corrected for the effects on the tape of operating
conditions, i.e. tensile forte, tape materials, thick-
The record tape Speed shall be in the range of
ness, and environment (temperature and humidity). 23,8 mm/s (15/16 in/s) to 6096 mm/s (240 in/s). lt
shall be appropriate for the input data rate so that
the flux transition density on tape is within the limit
3.62 tape Speed, nominal (IJ): A set of defined nom-
imposed by tableA.l for the Performance category
inal tape Speeds for tapes operating at the reference
tensile forte (see 4.4.7), and in Standard test en-
of the System concerned. The reproduce tape Speed
(+ 73 OF
vironmental conditions of 23 “C + 3 “C may be adjusted to obtain the desired output data
+ 5 “F) and relative humidity 45 % 6 55 %. rate. Tape Speed should be a matter of agreement
-
between the interchange Parties. Table 7 lists nom-
3.63 tape Speed error: Departure of the average inal recording tape Speeds and the associated flux
Speed from the nominal value. transition density limits.
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ISO/IEC 8441=2:1991(E)
4.2.2 Effective tape Speed
4.4 Recorder/reproducer characteristics
The effective tape Speed (v& throughout a reel (in
4.4.1 Data scatter
the absence of tape-derived servo Speed control)
shall be within + 0,5 % of each of the nominal tape
The maximum data scatter shall be as follows:
Speeds given in table 7 which are provided for by the
recorder/reproducer.
Tape width Maximum data scatter
12,7 mm (0,5 in) 2,54 Fm (100 Pin)
25,4 mm (1,0 in)
4.2.3 Pulse-to-pulse jitter 5,08 Fm (200 Pin)
50,8 mm (2,0 in) IO,16 pm (400 pin)
4.2.3.1 Intratrack. On any track, the pulse-to-pulse
4.4.2 Data azimuth (static)
jitter (0 to peak units) plotted against pulse-to-pulse
interval (in the absence of tape-derived Speed con-
Data azimuth (static) shall not be greater than
trol) shall have a slope less than 0,2 % at every
+ 0,3 mrad (k 1 ’).
Speed listed in table7 which is provided for by the
recorder/reproducer.
4.4.3 Data azimuth (dynamic)
NOTE 14 Recommended methods for measuring pulse-
to-pulse jitter are given in ISO 6068:1985, annex A.
Data azimuth (dynamic) shall not be greater than
+ 0,3 mrad (+ 1 ’) as determined from measure-
Gen& of the dynamic interchannel time displace-
4.2.3.2 Intertrack. Between any pair of adjacent
ment error (ITDE) between outer tracks on the Same
tracks on the Same head, the intertrack pulse-to-
head. The method for the measurement of ITDE shall
pulse jitter (0 to peak units) plotted against pulse-
be in accordance with ISO 6068.
to-pulse interval (in the absence of tape-derived
Speed control) shall have a slope less than 0,4 %
at all effective tape Speeds as 4.2.2. The effects of
4.4.4 Individual track data azimuth differente
skew tan be added, provided dynamic skew and
static skew Iimits in this part of ISO/IEC 8441 are not
The maximum Signal loss due to the individual track
exceeded.
data azimuth differentes shall not be greater than
1 dß (excluding reproduce head error) at the short-
est wavelength specified by the manufacturer of the
4.2.3.3 With tape-derived Speed control. With tape-
equipment. The Overall recoudlreproduce error shall
derived Speed control, the intertrack and intratrack
not be greater than 2 dß.
pulse-to-pulse jitter values shall not exceed twice
the values given in 4.2.3.2 and 4.2.3.1, respectively.
4.4.5 Head tilt
Head tilt shall not be greater than + 0,3 mrad (+ 1 ’)
(see figure 1).
4.3 Track configurations
Head mechanical Parameters shall be as shown in
4.4.6 Head polarity
figure 1. Track configurations shall be as shown in
figure2 for an n-track interlaced head, and the re-
4.4.6.1 Record side. Some recording Codes require
corded tape format shall be as shown in figure 3 with
that the recording and reproduce polarities bear a
dimensions given in the applicable table 1 to
known relationship to each other for correct decod-
table 6.
ing. To maintain Signal polarity from record to play-
back it is required that an isolated false-to-true level
NOTE 15 Although a tape reference edge is stated,
transition, followed by a return to the quiescent false
edge guiding of the tape is not an implied requirement of
the recorder/reproducer. level, at the encoder output be recorded as a
South-north north-South flux transition sequence on
The head spacing for adjustable heads refers to tape. Likewise, the passage of such an isolated
equipment having facilities for adjusting the azimuth South-north not-th-South flux transition sequence
of reproduce heads; these facilities are required for past the reproduce head shall Cause a positive-
high density digital recorders/reproducers in cate-
going output pulse to appear at the input to the de-
gory C and possibly category B (see annex A).
coder.
NOTE 16 For Cross-play enhancement, it may be bene- NOTE 17 Details as to how to establish known polarity
ficial to adjust the record head azimuth against a recorded flux transitions on tape will be found in 1SO 6068:1985,
reference tape aligned to the reproduce Systems. annex A .
5
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ISO/IEC 8441-2:1991 (E)
operating tensile forte departs from the reference
4.4.6,2 Reproduce side. Esch reproduce head
tensile forte, the corrections applied to make the
winding shall be connected to its respective ampli-
effective tape Speed (v& equal to the nominal tape
fier in such a manner that a Segment of tape
exhibiting a South-north north-South transition pat- Speed (17) become increasingly unreliable due to
nonlinearities, etc.
tern will produce a positive-going pulse, with re-
spect to System ground, at the output of the
reprod
...
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