ISO/IEC 9661:1994

lSO/IEC
INTERNATIONAL
9661
STANDARD
Second edition
1994-l 2-l 5
Information technology - Data
interchange on 12,7 mm wide magnetic
j
18 tracks, 1491 data
tape cartridges -
bytes per millimetre
- khange de don&es sur cartouches de
Technologies de I’informa tion
bande magnktique de 12,7 mm de large - 18 pistes, 1491 caractG.res
par millimi! tre
Reference number
lSO/IEC 9661 :I 994(E)

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ISO/IEC 9661:1994 (E)
Page
Contents
1
Section 1 - General
1
1
1
Conformance
2
1
Normative references
3
1
4 Definitions
1
4.1 Average signal amplitude
1
4.2 Back surface
1
Beginning of Tape (BOT)
4.3
1
4.4 Byte
1
4.5 Cartridge
1
4.6 Cyclic Redundancy Check character
1
4.7 Data density
1
Error Correcting Code
4.8
1
4.9 Flux transition position
2
4.10 Flux transition spacing
2
4.11 Magnetic tape
2
Master Standard Reference Tape
4.12
2
4.13 Physical recording density
2
4.14 Postamble
2
4.15 Preamble
2
Reference field
4.16
2
4.17 Secondary Standard Reference Tape
2
4.18 Standard reference amplitude
2
4.19 Standard reference current
2
Test recording current
4.20
2
4.21 Track
2
4.22 Typical field
2
5 Environment and safety
Cartridge/Tape testing environment
5.1
Cartridge operation environment
5.2
53 Cartridge storage environment
5:4 Safetv requirements
4
@ ISO/IEC 1994
All rights reserved. No part of this publication may be reproduced or utilized in any form or
by any means, electronic or mechanical, including photocopying and microfilm, without per-
mission in writing from the publisher
ISO/lEC Copyright Office * Case Postale 56 l CH-1211 Genbve 20 * Switzerland
Printed in Switzerland

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ISO/IEC 9661t1994 (E)
3
5.4.1 Safety
3
5.4.2 Flammability
3
5.5 Transportation
3
Section 2 - Tape requirements
3
6 Characteristics of the tape
Material
61
6:i Tape length
6.3 Tape width
. Tape discontinuity
64
65 Total thickness of tape
6:6 Base material thickness
67 Longitudinal curvature
6:8 Out-of-plane distortions
Cupping
69
Dynamic frictional characteristics
6’10 .
Frictional drag between the recording surface and the tape back surface
6.10.1
6.10.2 Frictional drag between the tape recording surface and ferrite after environmental cycling
Coating adhesion
6.11
Flexural rigidity
6.12
6.13 Electrical resistance of coated surfaces
6.14 Tape durability
6.15 Inhibitor tape
Tape abrasivity
6.16
Pre-recording condition
6.17
6.18 Magnetic recording characteristics
6.18.1 Typical field
Signal amplitude
6.18.2
Resolution
6.18.3
6.18.4 Overwrite
6.18.5 Narrow-Band Signal-to-Noise Ratio (NB-SNR)
Tape quality
6.19
10
Missing pulses
6.19.1
10
6.19.2 Missing pulse zones
10
6.19.3 Coincident missing pulse zones
10
3 - Cartridge requirements
Section
10
Dimensional and mechanical characteristics of the cartridge
7
11
7.1 Overall dimensions (figures 4 to 6)
11
5)
72 Write-inhibit mechanism (figures 4 and
11
7:3 Label area of the rear side (figures 5 and 6)
12
Label area of the top side (figure 5)
7.4
12
7.5 Case opening (figures 4,5,7 and 9)
12
7.6 Locating notches (figures 7,8 and 10)
13
Locating areas (figure 7)
7.7
13
Inside configuration of the case around the case opening (figures 7 and 11)
7.8
13
7.9 Other external dimensions of the case (figure 8)
13
7.10 Central window (figure 7)
13
7.11 Stacking ribs
14
7.12 Flexibility of the case
14
7.12.1 Requirements
. . .
111

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-
ISO/IEC 9661:1994 (E)
14
7.12.2 Procedure
14
7.13 Tape reel (figures 12 and 13)
14
Locking mechanism (figure 13)
7.13.1
15
Axis of rotation of the reel
7.13.2
15
7.133 Metallic insert
15
7.13.4 Toothed rim
15
7.13.5 Hub of the reel
15
Relative positions
7.13.6
16
7.13.7 Characteristics of the toothed rim (figure 12)
16
7.14 Leader block (figure 15)
17
7.15 Attachment of the tape to the leader block (figure 16)
17
Latching mechanism (figure 17)
7.16
18
7.17 Tape wind
18
7.18 Wind tension
18
7.19 Circumference of the tape reel
18
Moment of inertia
7.20
25
Section 4 - Recording requirements
25
8 Method of recording
25
8.1 Physical recording density
25
8.2 Bit cell length
25
Average bit cell length
83 .
25
84 l Long-term average bit cell length
25
85 0 Short-term average bit cell length
25
86 0 Rate of change
25
Bit shift
87 l
25
88 . Total character skew
26
89 Read signal amplitude
26
8’10 . Coincident missing pulses
26
9 Track format
26
9.1 Number of tracks
26
9.2 Reference edge
26
9.3 Track positions
26
9.4 Track width
26
Azimuth
9.5
26
10 Data format
27
10.1 Types of bytes
27
10.1.1 Data bytes
28
10.1.2 Pad bytes
28
10.2 Frame
29
10.3 Data Block
29
Prefix
10.3.1
?
29
10.3.2 Data Frames
30
10.3.3 Residual Frame 1
31
Residual Frame 2
10.3.4
32
10.3.5 Summary of requirements for Residual Frames
33
10.3.6 Suffix
33
10.4
Error Correcting Code (ECC)
33
10.4.1 Diagonal Redundancy Check (DRC)
iv

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ISO/IEC 9661:1994 (E)
34
10.4.2 Vertical Redundancy Check (VRC)
34
10.4.3 ECC Format
35
10.4.4 Summary of ECC
36
10.5 Recording of &bit bytes on the tape
36
10.6 Recorded Data Block
36
10.6.1 Preamble
36
10.6.2 Beginning of Data Mark (BDM)
36
10.6.3 Resync Control Frame
36
10.6.4 End of Data Mark (EDM)
36
Postamble
10.6.5
36
10.7 Data density
37
11 Tape format
37
11.1 Density Identification Burst
38
11.2 ID Separator Burst
38
113 Interblock Gaps
38
11.4 Erase Gaps
38
11.4.1 Normal Erase Gaps
38
11.4.2 Elongated Erase Gaps
38
Tape Marks
11.5
39
11.6 Relationship between Interblock Gaps, Erase Gaps and Tape Marks
39
11.6.1 Interblock Gap followed by a Tape Mark
39
11.6.2 Tape Mark followed by an Interblock Gap
39
11.6.3 Interblock Gap followed by an Erase Gap
39
11.6.4 Erase Gap followed by an Interblock Gap
40
11.6.5 Summary of the relationship between Interblock Gaps, Erase Gaps and Tape Marks
40
11.7 First and last recording on the tape
41
11.8 Summary of the tape format
41
11.8.1 Characteristics of recording other than recorded Data Blocks
41
11.8.2 Arrangement of recording on the tape
Annexes
42
A - Recommendations for transportation
43
B - Inhibitor tape
44
C - Tape abrasivity measurement procedure
47
D - Recommendations on tape durability
48
E - Pre-recording condition
49
F - Representation of &bit bytes by g-bit patterns
52
G - Measurement of bit shift
54
H - Dimensions of the cartridge ,

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ISO/IEC 9661t1994 (E) -
Foreword
IS0 (the International Organization for Standardization) and IEC (the Inter-
national Electrotechnical Commission) form the specialized system for worldwide
standardization. National bodies that are members of IS0 or IEC participate in the
development of International Standards through technical committees established
by the respective organization to deal with particular fields of technical activity.
IS0 and IEC technical committees collaborate in fields of mutual interest. Other
international organizations, governmental and non-governmental, in liaison with
IS0 and IEC, also take part in the work.
In the field of information technology, IS0 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 bodies for voting. Publication
as an International Standard requires approval by at least 75 % of the national
bodies casting a vote.
International Standard ISO/IEC 9661 was prepared by Joint Technical Committee
ISO/IEC JTC 1, Information technology, Subcommittee SC 11, Flexible magnetic
media for digital data interchange.
This second edition cancels and replaces the first edition (IS0 9661: 1988).
Annexes C, E, F and G form an integral part of this International Standard.
Annexes A, B, D and H are for information only.
vi

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ISO/IEC 9661:1994 (i3)
INTERNATIONAL STANDARD
Information technology - Data interchange on 12,7 mm wide magnetic tape
cartridges - 18 tracks, 1491 data bytes per millimetre
Section 1 - General
1 Scope
This International Standard specifies the physical and magnetic characteristics of a 12,7 mm wide, H-track magnetic tape
cartridge to enable interchangeability of such cartridges. It also specifies the quality of the recorded signals, the format and
recording method thus allowing, together with IS0 1001 for magnetic tape labelling, full data interchange by means of such
magnetic tape cartridges.
2 Conformance
A magnetic tape cartridge shall be in conformance with this International Standard if it meets all mandatory requirements
specified herein. The tape requirements shall be satisfied throughout the extent of the tape.
3 Normative references
The following standards contain provisions which, through reference in this text, constitute provisions of this International
Standard. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to
agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent
editions of the standards listed below. Members of IEC and IS0 maintain registers of currently valid International Standards.
ISO/IEC 646: 199 1, Information technology - IS0 7-bit coded character set for information interchange.
Part 13: Wrought stainless steels.
IS0 683-13: 1986, Heat-treatable steels, alloy steels and free-cutting steels -
IS0 1001: 1986, Information processing - File structure and labelling of magnetic tapes for information interchange.
IS0 1302: 1992, Technical drawings - Method of indicating su@ace texture.
ISO/IEC 2022: 1994, Information technology - Character code structure and extension techniques.
ISO/IEC 4873: 199 1, Information technology - IS0 &bit code for information interchange - Structure and rules for
implementation.
4 Definitions
For the purposes of this International Standard, the following definitions apply.
4.1 Average signal amplitude: The average peak-to-peak value of the signal output of the read head measured over a
minimum of 25,4 mm of tape exclusive of missing pulses.
4.2 Back surface: The surface of the tape opposite the magnetic coating used to record data.
4.3 Beginning of Tape (BOT): The point along the length of the magnetic tape indicated by the start of the Density
Identification Burst.
Byte: An ordered set of eight bits acted upon as a unit and recorded as a 9-bit pattern.
4.4
4.5 Cartridge: A container holding a supply reel of magnetic tape with an attached leader block.
4.6 Cyclic Redundancy Check character: A character represented by two bytes, placed at the end of a Data Block and
used for error detection.
Data density: The number of &bit bytes stored per unit length of tape, expressed in bytes per millimetre.
4.7
4.8 Error Correcting Code: A mathematical procedure yielding bits used for the detection and correction of errors.
1

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ISODEC 9661:1994 (E)
Flux transition position: That point which exhibits maximum free-space flux density normal to the tape surface.
4.9
4.10 Flux transition spacing: The distance along a track between successive flux transitions.
and retain the magnetic signals intended for input, output
4.11 Magnetic tape: A tape which will accept
purposes on computers and associated equipment.
amplitude, resolution
4.12 Master Standard Reference Tape: A tape selected as the for reference field, signal
and overwrite.
Note - A Master Standard Reference Tape has been established at the National Institute for Standards and Technology (NIST) for this International Standard.
4.13 Physical recording density: The number of recorded flux transitions per unit length of track, expressed in flux
transitions per millimetre (ftpmm).
4.14 Postamble: A repeated 9-bit pattern at the end of a recorded Data Block providing electronic synchronization when
reading in the reverse direction.
beginning recorded Data Block providing electronic synchronization
4.15 Preamble: A repeated 9-bit pattern at the of a
when reading in the forward direction
4.16 Reference field: The typical field of the Master Standard Reference Tape.
4.17 Secondary Standard Reference Tape: A tape the performance of which is in relation to that of the
Master
Standard Reference Tape.
Note - Secondary Standard Reference Tapes have been developed at the National Institute for Standards and Technology (NIST) and are available fkom the
NIST Office of Standard Reference Materials, Room 205, Building 202, National Institute of Standards and Technology, Gaithersburg, MA 20899, USA,
under reference number SRM 3202, until January 2004.
It is intended that these be used for calibrating tertiary reference tapes for use in routine calibration.
4.18 Standard reference amplitude: The average signal amplitude from the Master Standard Reference Tape when it is
recorded with the test recording current on the NIST measurement system at 972 ftpmm.
Traceability to the standard reference amplitude is provided by the calibration factors supplied with each Secondary Standard
Reference Tape.
4.19 Standard reference current: The current that produces the reference field.
4.20 Test recording current: The current that is 1,5 times the standard reference current.
4.21 Track: A longitudinal area on the tape along which a series of magnetic signals may be recorded.
4.22 Typical field: In the plot of the average signal amplitude against the recording field at the physical recording density
of 972 fipmm, the minimum field that causes an average signal amplitude equal to 85 % of the maximum average signal
amplitude.
5 Environment and safety
room and not to
Unless otherwise stated, the conditions specified below refer to the ambient conditions in the test or computer
those within the tape equipment.
51 0 Cartridge/Tape testing environment
Unless otherwise stated, tests and measurements made on the tape cartridge to check requirements of this International
Standard shall be carried out under the following conditions:
temperature: 23 “C k 2 “C
relative humidity: 40 % to 60 %
conditioning period
before testing: 24 hours.
52
l Cartridge operation environment
Cartridges used for data interchange shall be capable of operating under the following conditions:
temperature: 16 “C to 32 “C
relative humidity: 20 % to 80 %
2

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ISO/IEC 9661:1994 (E)
wet bulb temperature: 25 “C max.
The average temperature of the air immediately surrounding the tape shall not exceed 405 “C.
Note - Localized tape temperatures in excess of 49 “C may cause tape damage.
storage and/or transportation to conditions outside the
Conditioning before operating: If a cartridge has been exposed during
above values, it shall be conditioned for a period of at least 24 hours.
53 l Cartridge storage environment
Cartridges used for data interchange shall be stored under the following conditions.
temperature: 5 “C to 32 “C
relative humidity: 5 % to 80 %
wet bulb temperature: 26 “C max.
54 0 Safety requirements
5.4.1 Safety
The cartridge and its components shall not constitute any safety or health hazard when used in its intended manner or in any
foreseeable misuse in an information processing system.
5.4.2 Flammability
The cartridge and its components shall be made from materials which, if ignited from a match flame, do not continue to bum
in a still carbon dioxide atmosphere.
55 l Transportation
This International Standard does not specify parameters for the environment in which cartridges should be transported. Annex
A gives some recommendations for transportation.
Section 2 - Tape requirements
6 Characteristics of the tape
61 a Material
The tape shall consist of a base material (oriented polyethylene terephthalate film or its equivalent) coated on one side with a
strong, yet flexible layer of ferromagnetic material dispersed in a suitable binder. The back surface of the tape may also be
coated with a ferromagnetic or non-ferromagnetic material.
62 0 Tape length
The length of the tape shall not be less than 165 m.
Tape width
63 l
The width of the tape shall be 12,650 mm & 0,025 mm. The width shall be measured across the tape from edge-to-edge when
the tape is under a tension of less than 0,28 N.
64 l Tape discontinuity
There shall be no discontinuities in the tape such as those produced by tape splicing or perforations.
65 l Total thickness of tape
The total thickness of the tape at any point shall be between 0,0259 mm and 0,0337 mm.
66 a Base material thickness
The thickness of the base material shall be 0,0234 mm nominal.
67 l Longitudinal curvature
The radius of curvature of the edge of the tape shall not be less than 33 m.

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ISO/IEC 9661:1994 (E)
Procedure
Allow a length of tape of 1 m to unroll and assume its natural curvature on a flat smooth surface. Measure the deviation from a
1 m chord. The deviation shall not be greater than 3,8 mm. This deviation corresponds to the minimum radius of curvature of
33 m if measured over an arc of circle.
68 0 Out-of-plane distortions
All visual evidence of out-of-plane distortion shall be removed when the tape is subjected to a uniform tension of 0,6 N.
Out-of-plane distortions are local deformations which cause portions of the tape to deviate from the plane of the surface of the
tape. Out-of-plane distortions are most readily observed when the tape is lying on a flat surface under no tension.
69 l Cupping
The departure across the width of tape from a flat surface shall not exceed 0,3 mm.
Procedure
Cut a length of tape of 1,O m k 0,l m . Condition it for a minimum of 3 hours in the test environment by hanging it so that the
coated surface is freely exposed to the test environment. From the centre portion of the conditioned tape cut a test piece of
length 25 mm. Stand the test piece on its end in a cylinder which is at least 25 mm high with an inside diameter of 13,0 mm 2
0,2 mm. With the cylinder standing on an optical comparator measure the cupping by aligning the edges of the sample to the
reticle and determining the distance from the aligned edges to the corresponding surface of the test piece at its centre.
6.10 Dynamic frictional characteristics
In the tests of 6.10.1 and 6.10.2 the specified forces of 1,O N and 150 N, respectively, comprise both the force component of
the dynamic friction and the force of 064 N applied to the test piece of tape.
NOTE - Particular attention should be given to keeping the surfaces clean.
6.10.1 Frictional drag between the recording surface and the tape back surface
The force required to move the recording surface in relation to the back surface shall not be less than 1,0 N.
Procedure
Wrap a test piece of tape around a 254 mm diameter circular mandrel with the back surface of the test piece facing out-
9
ward.
ii) Place a second test piece of tape, with the recording surface facing in, around the first test piece for a total angle of wrap
of 90”.
iii) Apply a force of 0,64 N to one end of the outer test piece of tape. Secure its other end to a force gauge which is mounted
on a motorized linear slide.
iv) Drive the slide at a speed of 1 mm/s.
6.10.2 Frictional drag between the tape recording surface and ferrite after environmental cycling
The force required to move the tape at a point 1,34 m from the leader block of the cartridge shall not be greater than 1,50 N.
The force required at a point 4,3 m from the junction of the tape with the cartridge hub shall not exceed the first force by more
than a factor of 4.
Procedure
Wind tape on to a spool hub of diameter 50 mm to an outside diameter of 97 mm with a winding tension of 2,2 N sf:
0
0,2 N.
ii)
Repeat the following two steps five times:
Store for 48 hours at a temperature of 50 “C and a relative humidity of 10 % to 20 %.
a)
Acclimatize in the testing environment for 2 hours and rewind with a tension of 2,2 N k 0,2 N.
b)
iii) Condition the tape for 48 hours at a temperature of 30,5 “C and a relative humidity of 85 %. The tape shall remain in
this environment for steps iv) and v).

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ISO/IEC 9661:1994 (E)
iv) Apply a force of 0,64 N to one end of a test piece of tape of not more than 1 m, taken 1,34 m from the leader block. Pass
the test piece over a ferrite rod of diameter 25,4 mm with the recording surface in contact with the rod for a total angle
of wrap of 90”.
The rod shall be made from the ferrite specified in annex C. It shall be polished to a roughness value ra of 0,05 pm
(roughness grade N2, IS0 1302). Pull the other end of the test piece horizontally at 1 mm/s.
Repeat step iv) for a similar test piece taken 4,3 m from the junction of the tape with the cartridge hub.
VI
6.11 Coating adhesion
The force required to peel any part of the coating from the tape base material shall not be less than 1,5 N.
Procedure
Take a test piece of the tape approximately 380 mm long and scribe a line through the recording coating across the
9
width of the tape 125 mm from one end.
. . .
Using a double-sided pressure sensitive tape, attach the full width of the test piece to a smooth metal piece plate, with
11)
the recording surface facing the plate, as shown in the figure below.
iii) Fold the test piece over 180”, attach the metal plate and the free end of the test piece to the jaws of a universal testing
machine and set the speed of the jaw separation to 254 mm per min.
iv) Note the force at which any part of the coating first separates from the base material. If this is less than 1,5 N, the test
has failed. If the test piece peels away from the double-sided pressure sensitive tape before the force exceeds 1,5 N, an
alternative type of double-sided pressure sensitive tape shall be used.
If the back surface of the tape is coated, repeat i) to iv) for the back coating.
Scribed line
Pressure-sensitive tape
a 125 mm -
Figure 1 - Coating adhesion
6.12 Flexural rigidity
The flexural rigidity of the tape in the longitudinal direction shall be between 0,06 N-mm2 and 0,16 N*mm2.
Procedure
Clamp a 180 mm test piece of tape in a universal testing machine, allowing a 100 mm separation between the machine jaws.
Set the jaw separation speed at 5 mm per minute. Plot force against distance. Calculate the flexural rigidity using the slope of
the curve between 2,2 N and 6,7 N by the formula:
E dF/WT
-
-
dL/L
I =WT3/12

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ISO/IEC 9661:1994 (E)
Flexural rigidity = El
where :
6F = change in force in N
= measured thickness in mm
T
= measured width in mm
W
a/L = change in lenght of test piece between the jaws divided by the original length between the jaws.
6.13 Electrical resistance of coated surfaces
The electrical resistance of any square area of the recording surface shall be within the range:
-
1 O5 IR to 5 x lo* Sz for non-backcoated tapes;
-
105 Q to 5 x lo9 Sz for backcoated tapes.
The electrical resistance of any backcoating shall be less than lo6 52.
Procedure
Condition a test piece of tape to the test environment for 24 hours. Position the test piece over two 24-carat gold-plated,
semi-circular electrodes having a radius r - - 25,4 mm and a finish of at least N4, so that the recording surface is in contact with
each electrode. These electrodes shall be placed parallel to the ground and parallel to each other at a distance d = 12,7 mm
between their centres. Apply a force F of 1,62 N to each end of the test piece. Apply a d.c. voltage of 500 V k 10 V across the
electrodes and measure the resulting current flow. From this value, determine the electrical resistance.
Repeat for a total of five positions along the test piece and average the five resistance readings. For back-coated tape repeat the
procedure with the backcoating in contact with the electrodes.
F F
Figure 2 - Position of test piece over two semi-circular electrodes
When mounting the test piece, make sure that no conducting paths exist between the electrodes except that through the coating
under test.
Note - Particular attention should be given to keeping the surfaces clean.
4
6.14 Tape durability
This International Standard does not specify parameters for assessing tape durability.
However, a recommended procedure is described in annex D.
6.15 Inhibitor tape
This International Standard does not specify parameters for assessing whether or not a tape is an inhibitor tape.
However, annex B gives further information on inhibitor tapes.
6

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ISO/IEC 9661:1994 (E)
6.16 Tape abrasivity
Tape abrasivity is the tendency of the tape to wear the tape transport. The length of the wear pattern on a wear bar shall not
exceed 56 pm when measured as specified in annex C.
6.17 Pre-recording condition
Prior to recording data or to testing, the tape shall have been erased using alternating magnetic fields of decaying levels
(anhysteretic process) to ensure that the remanent magnetic moment of the recording surface does not exceed 20 % of the
maximum remanent magnetic moment. Annex E specifies the method of measurement.
In addition no low density transitions shall be present on the tape.
6.18 Magnetic recording characteristics
The magnetic recording characteristics shall be as defined by the testing requirements given below.
When performing these tests, the output or resultant signal shall be measured on the same relative pass for both a tape
calibrated to the Master Standard Reference Tape and the tape under test (read-while-write or first forward-read-pass) on the
same equipment.
The following conditions shall apply to the testing of all magnetic recording characteristics, unless otherwise stated:
-
tape condition : pre-recording condition
tape speed : not greater than 2,5 m/s
read-track : within the written track
-
azimuth alignment : not greater than 6’ between the mean write transitions and the read gap
: 1,4~m+0,2~m
write-gap length
write head saturation density : 0,34 T & 0,03 T
-
tape tension : 2,2 N AZ 0,2 N
-
recording current : test recording current
6.18.1 Typical field
The typical field of the tape shall be between 90 % and 110 % of the reference field.
Reference
Traceability to the reference field is provided by the calibration factors supplied with each Secondary Standard
Tape.
6.18.2 Signal amplitude
The average signal amplitude at the physical recording density of 972 ftpmm shall be between 70 % and 140 % of the standard
reference amplitude.
Traceability to the standard reference amplitude is provided by the calibration factors supplied with each Secondary Standard
Reference Tape.
6.18.3 Resolution
The ratio of the average signal amplitude at the physical recording density of 1 458 ftpmm to that at the physical recording
density of 972 ftpmm shall be between 80 % and 120 % of the same ratio for the Master Standard Reference Tape.
Traceability to the resolution of the Master Standard Reference Tape is provided by the calibration factors supplied with each
Secondary Standard Reference Tape.
6.18.4 Overwrite
Overwrite is the ratio of the average signal amplitude of the residual of the fundamental frequency of a tone pattern after being
overwritten at 972 ftpmm to the average signal amplitude of the 972 ftpmm signal. The average signal amplitude of the tone
pattern is the peak-to-peak amplitude of the sinusoidal signal with equal rms power.
6.18.4.1 Requirement
The overwrite for the tape shall be less than 120 % of the overwrite for the Master Standard Reference Tape.
Traceability to the overwrite of the Master Standard Reference Tape is provided by the calibration factors supplied with each
Secondary Standard Reference Tape.
Procedure

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ISO/IEC 9661:1994 (E)
Record a tone pattern which shall be the following sequence of flux transitions:
where: al = 1,029 pm
a2 = 0,514 pm
Record a 972 ftpmm signal over the tone pattern. Measure the average signal amplitude of the residual of the fundamental
frequency of the tone pattern (one sixth of the frequency of the 972 ftpmm signal) and the average signal amplitude of the 972
ftpmm signal. Both amplitude measurements should be made using suitable filters.
6.18.5 Narrow-Band Signal-to-Noise Ratio (NB-SNR)
The narrow-band signal-to-noise ratio is the average signal amplitude rms power divided by the average integrated (side band)
rms noise power, and is expressed in dB.
6.18.5.1 Requirement
The NB-SNR ratio shall be equal to, or greater than, 30 dB when normalized to a track width of 410 pm. The normalization
factor is dB(410) = dB(W) + 10 log 410/W, where W is the track width used when measuring dB(W).
6.18.5.2 Procedure
The NB-SNR ratio shall be measured using a spectrum analyzer with a resolution bandwidth (RBW) of 1 kHz and a video
bandwidth (VBW) of 10 Hz. The tape speed shall be 762 mm/s for the frequencies specified below.
The NB-SNR ratio shall be measured as follows:
Measure the read-signal amplitude of the 972 ftpmm signal, taking a minimum of 150 samples over a minimum length
of tape of 46 m.
ii) On the next pass (read only) measure the rms noise power over the same section of tape and integrate the rms noise
power (normalizing for the actual resolution bandwidth) over the range from 332 kHz to 366 kH
...