Helical-scan video tape cassette system using 12,65 mm (0,5 in) magnetic tape on type L

Applies to magnetic video recording and/or reproduction using 12,65 mm (0,5 in) tape on helical-scan video cassette recorders suitable for broadcast applications.

Video-Bandkassettensystem mit Schrägspuraufzeichnung auf Magnetband 12,65 mm (0,5 in) L-Format

Système de magnétoscope à cassette à balayage hélicoïdal utilisant la bande magnétique de 12,65 mm (0,5 in) de format L

S'applique à l'enregistrement et/ou à la lecture magnétique vidéo des cassettes à bande magnétique de 12,65 mm (0,5 in) de large sur les magnétoscopes à cassettes à balayage hélicoïdal convenant aux applications en radiodiffusion.

Helical-scan video tape cassette system using 12,65 mm (0,5 in) magnetic tape on type L (IEC 60961:1993)

General Information

Status
Published
Publication Date
31-Mar-1999
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
01-Apr-1999
Due Date
01-Apr-1999
Completion Date
01-Apr-1999

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SLOVENSKI STANDARD
SIST EN 60961:1999
01-april-1999
Helical-scan video tape cassette system using 12,65 mm (0,5 in) magnetic tape on
type L (IEC 60961:1993)
Helical-scan video tape cassette system using 12,65 mm (0,5 in) magnetic tape on type
L
Video-Bandkassettensystem mit Schrägspuraufzeichnung auf Magnetband 12,65 mm
(0,5 in) L-Format
Système de magnétoscope à cassette à balayage hélicoïdal utilisant la bande
magnétique de 12,65 mm (0,5 in) de format L
Ta slovenski standard je istoveten z: EN 60961:1994
ICS:
33.160.40 Video sistemi Video systems
SIST EN 60961:1999 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN 60961:1999

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SIST EN 60961:1999

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SIST EN 60961:1999

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SIST EN 60961:1999

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SIST EN 60961:1999

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SIST EN 60961:1999
NORME CEI
INTERNATIONALE IEC
961
INTERNATIONAL
Deuxième édition
STANDARD
Second edition
1993-12
Système de magnétoscope à cassette
à balayage hélicoïdal utilisant
la bande magnétique de 12,65 mm (0,5 in)
de format L
Helical-scan video tape cassette
system using 12,65 mm (0,5 in)
magnetic tape on type L
© CEI 1993 Droits de reproduction réservés — Copyright — all rights reserved
Aucune partie de cette publication ne peut âtre reproduite ni No part of this publication may be reproduced or utilized in
utilisée sous quelque forme que ce soit et par aucun pro- any form or by any means, electronic or mechanical,
including photocopying and microfilm, without permission
cédé, électronique ou mécanique, y compris la photocopie et
les microfilms, sans raccord écrit de l'éditeur. in writing from the publisher.
Bureau Central de la Commission Electrotechnique Internationale 3, rue de Varembé Genève, Suisse
Commission Electrotechnique Internationale
CODE PRIX ii
International Electrotechnical Commission
PRICE CODEPRICE CODE
IEC MextuyHaponHaA 3nettrpoTeXHH4ecMaa
HOMHCCHA
Pour prix, voir catalogue en vigueur
• ^
For price, see current catalogue

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SIST EN 60961:1999
961 ©IEC:1993 - 3 -
CONTENTS
Page
FOREWORD 9
Clause
SECTION ONE: GENERAL
11
1 Scope
11 2 Normative references
11 3 Environment and test conditions
11
Environment
3.1
13
3.2 Reference tape
13
Calibration tape 3.3
SECTION TWO: VIDEO TAPE AND VIDEO TAPE CASSETTE
SECTION THREE: VIDEO CASSETTE RECORDERS

15
4 Definitions of terms
15
Scanner 4.1
15
4.2 Drum
15 4.3 Upper drum
15
4.4 Lower drum
15 4.5 Effective drum diameter
17
4.6 Helix angle
17
4.7 Track angle
17 4.8 Centre span tension
17
4.9 Wrap angle
17
4.10 Lead signal overlap
17
5 Scanner pole-tips
17 5.1 Pole-tip projection
17
5.2 Luminance pole-tips
17 5.3 Colour-recording pole-tips
5.4 Erase pole-tips 19
19
5.5 Channel identification
Helix angle 19
6
19
7 Drum diameter and tape tension
19 7.1 Actual upper drum diameter
19
7.2 Actual lower drum diameter
7.3 Upper drum 19
21 7.4 Centre span tension

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SIST EN 60961:1999
961 © I EC:1993 – 5 –
Page
Clause
21
Dimensions and location of records 8
21
Test environment 8.1
21 8.2 Tape speed
21
Recording locations and dimensions 8.3
21
8.4 Curvature of video recordings
23
Relative positions of recorded signals 8.5
23 8.6 Gap azimuth
23
9 Luminance and colour-recording system
23
10 Recording characteristics
SECTION FOUR: RECORDING CHARACTERISTICS
23
11 Video recording
25 11.1 Luminance channel
31 11.2 Chrominance channel
35 11.3 Decoding and colour-field identification
37 12 Longitudinal audio signal recording (channels 1 and 2)
37
12.1 Reference levels
37 12.2 Frequency response
39
12.3 Track usage
41 13 FM audio signal recording (channels 3 and 4)
41
13.1 Signal processing
41
13.2 Reference levels
43 13.3 Noise reduction
43
13.4 Frequency modulation
43 13.5 Recording current
45
13.6 Track usage
45 14 Time and control code recording
45
14.1 Designated track for time and control code
45 14.2 Recording method
45 15 Tracking control recording
45 15.1 Tracking control signal
47 15.2 Tracking control and video timing
47
15.3 Recording method
SECTION FIVE: TYPE–L FORMAT VIDEO TAPE AND VIDEO TAPE CASSETTE
47 16 Mechanical characteristics of video tape cassette
47
16.1 Cassette outside dimensions
47
16.2 Datum planes

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SIST EN 60961:1999
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961 ©IEC:1993
Page
Clause
47
16.3 Window area and label area
47
16.4 Manufacturer's identification holes
16.5 Safety tab and safety plug 49
51
16.6 Reel
51
16.7 Cassette lid
51
17 Magnetic tape
51 17.1 Type of magnetic tape
53 17.2 Tape width
53 17.3 Tape thickness and length
53
17.4 Coercivity
53
17.5 Transmissivity
53 17.6 Offset yield strength
55 17.7 Residual elongation
55 17.8 Magnetic orientation
55
18 Leader tape/trailer tape
55
18.1 Mechanical characteristics
55
18.2 Leader tape and trailer tape dimensions
57
18.3 Offset yield strength
57
18.4 Splicing break strength
61
Figures
Annexes
135 A Cross tape track measurement technique
139
Reference tapes B

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SIST EN 60961:1999
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961 ©IEC:1993
INTERNATIONAL ELECTROTECHNICAL COMMISSION
HELICAL-SCAN VIDEO TAPE CASSETTE SYSTEM
USING 12,65 mm (0,5 in) MAGNETIC TAPE
ON TYPE L
FOREWORD
The IEC (International Electrotechnical Commission) is a worldwide organization for standardization
1)
comprising all national electrotechnical committees (IEC National Committees). The object of the IEC is to
promote international cooperation on all questions concerning standardization in the electrical and
electronic fields. To this end and in addition to other activities, the IEC publishes International Standards.
Their preparation is entrusted to technical committees; any IEC National Committee interested in
the subject dealt with may participate in this preparatory work. International, governmental and
non-governmental organizations liaising with the IEC also participate in this preparation. The IEC
collaborates closely with the International Organization for Standardization (ISO) in accordance with
conditions determined by agreement between the two organizations.
2) The formal decisions or agreements of the IEC on technical matters, prepared by technical committees on
which all the National Committees having a special interest therein are represented, express, as nearly as
possible, an international consensus of opinion on the subjects dealt with.
3) They have the form of recommendations for international use published in the form of standards, technical
reports or guides and they are accepted by the National Committees in that sense.
4) In order to promote international unification, IEC National Committees undertake to apply IEC International
Standards transparently to the maximum extent possible in their national and regional standards. Any
divergence between the IEC Standard and the corresponding national or regional standard shall be clearly
indicated in the latter.
International Standard IEC 961 has been prepared by sub-committee 60B: Video
recording, of IEC technical committee 60: Recording.
This second edition cancels and replaces the first edition published in 1989.
The text of this standard is based on the following documents:
DIS Report on Voting
60B(CO)152 60B(CO)168
Full information on the voting for the approval of this standard can be found in the repo rt
on voting indicated in the above table.
Annexes A and B are for information only.

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SIST EN 60961:1999
961 ©IEC:1993 - 11 -
HELICAL-SCAN VIDEO TAPE CASSETTE SYSTEM
USING 12,65 mm (0,5 in) MAGNETIC TAPE
ON TYPE L
SECTION ONE: GENERAL
1 Scope
This International Standard applies to magnetic video recording and/or reproduction using
12,65 mm (0,5 in) tape cassettes on helical-scan video cassette recorders suitable for
broadcast applications.
This standard specifies two recording modes. MODE I uses oxide particle tape, MODE II
uses metal particle tape and permits frequency modulated (FM) audio signals to be
recorded. The standard defines the electrical and mechanical characteristics of equipment
which will provide for interchangeability of recorded casse ttes. The requirements given are
related to 525 line-60 field and/or 625 line-50 field systems.
2 Normative references
The following normative documents 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 normative documents 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 normative documents indicated
below. Members of IEC and ISO maintain registers of currently valid International
Standards.
IEC 94-1: 1981, Magnetic tape sound recording and reproducing systems - Part 1:
General conditions and requirements
IEC 268-17: 1990, Sound system equipment - Part 17: Standard volume indicators
IEC 461: 1986, Time and control code for video tape recorders
IEC 767: 1983, Helical-scan video tape cassette system using 12,65 mm (0,5 in) magnetic
tape on type beta format
CCIR Repo rt 624-4: Characteristics of television systems
3 Environment and test conditions
3.1 Environment
Test and measurement made on the system to check the requirements of this standard
shall be carried out under the following conditions.

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SIST EN 60961:1999
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961©IEC:1993
Temperature (drum diameter): 20 °C ± 0,5 °C
20 °C ± 1 °C
Temperature (all other tests):
48%to52%
Relative humidity:
86 kPa to 106 kPa
Barometric pressure:
24 h
Conditioning before testing:
3.2 Reference tape
Blank tape to be used for reference recordings may be purchased from the manufacturers
listed in annex B. The electromagnetic compatibility parameters and their specifications
should be specified by the manufacturers and controlled accordingly.
Model name:
a) IEC L-format reference tape for MODE I;
IEC L-format reference tape for MODE II.
b)
Electromagnetic compatibility parameters and their specifications are indicated in
annex B.
3.3 Calibration tape
Calibration tapes which have satisfied the following requirements will be available from
manufacturers of video tape recorders and players in accordance with this format specifi-
cation.
Record locations and dimensions
3.3.1
For calibration tapes intended for the purpose of calibrating the mechanical accuracy of
the recorder or player, in accordance with this format specification, a 50 % reduction in the
tolerances shown in table 7 should, in general, be applied. If necessary, the record
locations and dimensions can be specially modified for certain calibration tapes in order to
avoid calibration error or to aid calibration.
3.3.2 Calibration signals
Two classes of signals should be recorded on the calibration tapes:
a) a series of conventional test signals for analogue component video tape recorders
Longitudinal audio
Video
- 1 kHz 0 VU
Colour bars (75 % or 100 %) -
- 15 kHz or 10 kHz 0 VU
- Multi-burst
- 40 Hz -20 VU
- Bow-tie (50 %)
-20 VU
- 1 kHz
- Pulse and bar
- 7 kHz -20 VU
FM audio
- 10 kHz -20 VU
- 400 Hz, 25 kHz deviation
-20 VU
- 400 Hz, 75 kHz deviation - 15 kHz

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SIST EN 60961:1999
961 ©IEC:1993 –15 –
b) special test signals developed by each manufacturer for product alignment. These
signals are not universally applicable to all manufacturers' products, and will not be
specified.
SECTION TWO: VIDEO TAPE AND VIDEO TAPE CASSETTE
This video tape recording system specifies the use of video tape and video tape cassette
in the BETA-format as delineated in sections two and four of IEC 767 or the use of video
tape and video tape cassette in the type-L format as delineated in section five of this
standard, which is newly specified to provide all-inclusive specifications of video tape and
video tape cassette for MODE Il recordings and/or long-playing operations including
current video tape and video tape cassette (see 16.1 through 18.4 of this standard).
SECTION THREE: VIDEO CASSETTE RECORDERS
4 Definitions of terms
The following definitions are given to assist in the correct understanding of this Inter-
national Standard.
4.1 Scanner
The mechanical assembly containing a drum, rotating pole-tips and tape-guiding elements.
It is used to record and reproduce video tape recordings.
4.2 Drum
The circular cylinder around which tape is at least partially wrapped in order to form the
head-to-tape inte rface of a video tape recording system.
4.3 Upper drum
That part of the drum in a helical-scan video recording system which does not come into
contact with the reference edge of the tape.
4.4 Lower drum
That part of the drum in a helical-scan video recording system which comes into contact
with the reference edge of the tape and usually contains tape-guiding elements.
4.5 Effective drum diameter
The value of drum diameter which, when used in theoretical calculations, will correspond
to the actual video record produced in a helical-scan video tape recording system. The
effective value is equal to or greater than the actual diameter.

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SIST EN 60961:1999
– 17 –
961 © I EC:1993
4.6 Helix angle
The angle formed between the path of the rotating pole-tips and the tape-reference-edge
guiding system on the scanner of a helical-scan video tape recording system.
4.7 Track angle
The angle of the recorded video track with respect to the reference edge of the tape in a
helical video tape recording.
4.8 Centre span tension
The calculated value of tape tension at a point midway between tape entrance and exit
guides of the scanner in a video tape recording system.
4.9 Wrap angle
The angle at the centre of the drum rotation subtended by the line of contact between the
drum and the reference edge of the tape.
4.10 Lead signal overlap
That portion of the helical record which is required to provide a duplicate (overlap)
recording.
5 Scanner pole-tips
There shall be four circumferential pole-tip locations as shown in figure 1 (top view).
5.1 Pole-tip projection
mm, measured from the outer surface
Each pole-tip projection shall be radially 0,04
+0,0,
of the upper drum to the end of the pole-tip.
5.2 Luminance pole-tips
180° ± 0,003° shall be provided for recording the
Two pole-tips circumferentially spaced at
luminance signal.
5.3 Colour-recording pole-tips
Each luminance pole-tip shall have associated with it a pole-tip for recording the time-
multiplexed colour signals and, when applicable, the FM audio signals.
A colour-recording pole-tip shall be located at a chordal distance of 4,396 mm ± 0,010 mm
in a counter-rotational direction from its associated luminance pole-tip, as shown in fgure 2,
mm
and shall be axially displaced from its associated luminance pole-tip by 0,0745
mm, in a direction away from the reference edge of the tape as shown in figure 2.
± 0,003

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SIST EN 60961:1999
961 ©IEC:1993 – 19 –
5.4 Erase pole-tips
If the erase pole-tips are employed, each luminance/colour-recording pole-tip pair shall
have an associated erase pole-tip located at any angle with respect to the luminance pole-
tip of the pair, in the direction of rotation as shown in figure 1.
5.5 Channel identification
Suitable means shall be provided, such as a pulse generator producing one pulse per
drum revolution, to permit the identification of the luminance/colour-recording pole-tip
pair which records field 1. This pair shall be identified as channel 1, and the remaining
pair shall be identified as channel 2.
6 Helix angle
The helix angle shall be 4,600° ± 0,003°.
7 Drum diameter and tape tension
Effective drum diameter, tape tension, helix angle, and tape speed completely determine
the video record track angle. Different methods of design and/or minor variations in drum
diameter and tape tension shall produce equivalent recordings for interchange purposes.
Values and operating conditions specified in this clause will produce the reference value
of track angle.
7.1
Actual upper drum diameter
ô,008 (2,933+00,00032
The actual upper drum diameter shall be 74,487 mm in). New techno-
logies and techniques are enabling compatible and interchangeable tapes to be produced
by recorders in which some of the dimensions of the transport scanning mechanism are
significantly changed. This can enable recorders to be made smaller and lighter for
portable applications by the use of a smaller scanning drum assembly. Such an approach
has been used for ENG applications.
7.2 Actual lower drum diameter
+0,000 +0,00000
74,487 The actual lower drum diameter shall be mm (2,933 in). New techno-
-0,008 0 00032
logies and techniques are enabling compatible and interchangeable tapes to be produced
by recorders in which some of the dimensions of the transport scanning mechanism are
significantly changed. This can enable recorders to be made smaller and lighter for
portable applications by the use of a smaller scanning drum assembly. Such an approach
has been used for ENG applications.
7.3 Upper drum
The upper drum shall rotate in synchronism with the video head tips.

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SIST EN 60961:1999
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961 © I EC:1993
7.4 Centre span tension
The centre span tension shall be 0,46 N ± 0,05 N.
8 Dimensions and location of records
This clause specifies the dimensions and locations of the video, audio and tracking control
records.
Test environment
8.1
8.1.1 In addition to the general environmental requirements of clause 3, the following
additional conditions shall be met in order to meet requirements of clause 8:
tape tension: 0,46 N ± 0,05 N.
8.1.2 Conditioning before recording and testing
Environmental: stabilized at the measurement conditions.
Tape tension: wound on a reel at 0,56 N ± 0,20 N.
8.1.3 The reference edge of the tape for dimensions in this standard shall be the lower
edge as shown in figures 3, 4a and 4b. The magnetic coating of the tape faces the
observer in all figures.
Tape speed
8.2
8.2.1 The tape speed shall be 118,582 mm/s ± 0,2 mm/s for 525 line-60 field systems.
8.2.2 The tape speed shall be 101,510 mm/s ± 0,2 mm/s for 625 line-50 field systems.
8.3 Recording locations and dimensions
8.3.1 Recording locations and dimensions shall be as specified in figures 3, 4a and 4b
and in table 7.
and 0 are shown for reference purposes only.
8.3.2 Dimensions P, R, W
rt ,
The actual value of these dimensions is determined by the parameters of the transpo
the tape speed and their tolerances. Direct measurement of the actual value of these
Q may be impractical; therefore, these dimensions should be
dimensions and dimension
made by an indirect measurement method, such as that specified in 8.4.
8.4 Curvature of video recordings
The edge of the video recording shall be contained within two parallel straight lines
0,010 mm apa rt .

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SIST EN 60961:1999
961 ©IEC:1993 – 23 –
Relative positions of recorded signals
8.5
8.5.1 Video luminance, video chrominance, tracking control, audio and time code signals
with information intended to be time coincident shall be positioned as shown in figures 4a
and 4b.
8.5.2 As shown in figures 4a and 4b, even-numbered fields have a different video
luminance and video chrominance phasing, due to the odd number of lines in a television
frame.
Gap azimuth
8.6
8.6.1 The azimuth of the audio, tracking control and time code head gaps used to
produce longitudinal track records shall be perpendicular to the direction of relative head-
to-tape motion.
8.6.2 The azimuth of the video head gaps for the luminance signal shall be –15° 15' and
signal shall be +15° 15' to the perpendicular to the direction of head
for the chrominance
motion.
9 Luminance and colour-recording system
Each pass of a luminance/colour-recording pole-tip pair shall record one television field,
plus an overlap.
10 Recording characteristics
The recording characteristics of video cassette recorders shall be in accordance with the
requirements specified in section four.
SECTION FOUR: RECORDING CHARACTERISTICS
11 Video recording
The video recording system shall provide separate and distinct signal paths for the
luminance and chrominance components. These component signals shall be recorded on
two separate tracks, designated as the Y track for the luminance signal, and the C track
for the chrominance signal. The C track shall record both R-Y and B-Y colour difference
signals in the form of a compressed time division multiplexed signal and, when applicable,
FM audio signals. Monochrome signals shall be recorded on the Y track, with the C track
recording only a blanking level signal and horizontal timing pulse.
Two modes of operation are defined for the following tape types:
oxide particle tape: MODE I;
metal particle tape: MODE II.
Sensing of tape type shall be automatic by means of a sensing hole in the cassette as
described in section five.

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SIST EN 60961:1999
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961 ©IEC:1993
11.1 Luminance channel
11.1.1 Signal processing
A signal processing system as specified in this clause shall contain in the order of the
signal flow the following elements:
rtion of the luminance signal.
11.1.1.1 A means of modifying the sync po
ical interval subcarrier in MODE II when the signal to
rt
11.1.1.2 A means of inserting a ve
be recorded has been decoded from a composite signal source which is defined in
SECAM
ical interval subcarrier (VISC) is not recorded in the
CCIR repo rt 624-4. The ve rt
system and shall be optional in MODE I.
11.1.1.3 A video detail enhancement process.
11.1.1.4 A video pre-emphasis network.
11.1.1.5 A means of clipping the video signal after pre-emphasis.
11.1.1.6 A linear frequency modulator having constant deviation with respect to the ampli-
tude of the modulating frequencies.
11.1.1.7 An amplifier of the frequency modulated carrier signal to provide alternating
current drives to the Y channel record heads.
11.1.2 Modification of the sync portion
A means shall be used to modify the pulse width and amplitude of the horizontal sync
ion as shown in figures 5a and 5b.
port
Luminance detail enhancement
11.1.3
The video signal shall receive detail enhancement with the characteristics shown in
table 1.

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SIST EN 60961:1999
961 © I EC:1993 - 27 -
Table 1 - Detail enhancement output (dB)
Input
Frequency dB
Hz
-30 -20 -15 -10 -5 0
0,2
200 k 0,4 0,4 0,4 0,4 0,3
500 k 1,9 1,7 1,7 1,4 0,8 0,4
0,7
1,0 M 4,6 4,0 3,5 2,4 1,3
1,5 M 6,7 4,6 3,0 1,6 0,9
5,6
3,3 1,1
2,0 M 8,0 6,6 4,9 1,8
3,0 M 9,5 7,5 5,3 3,6 2,2 1,3
1,4
4,0 M 9,9 7,6 5,3 3,6 2,2
5,0 M 9,9 7,3 5,1 3,3 2,0 1,2
NOTES
1 The video signal input level, including synchronization tip, is 1,0 Vpp.
The play-back response is such that the recording response is compensated during play-back.
2
at 3,5 MHz prior to
3 The phase of side chain signal shall be equal to the phase of input signal 43 1
t2
mixing.
(Di Input Output
o
0 0
2
High pass Low pass
Limiter
filter filter
MC 288193
11.1.4 Luminance pre-emphasis
The pre-emphasis is defined by the frequency and phase characteristics of the network
shown in figure 6, when fed from a zero impedance source, and feeding an infinite
impedance load.
11.1.5
Amplitude clipping
For an input signal where synchronization tip is at 0 % and peak white at 100 %, any
positive or negative amplitude excursion exceeding the levels shown in table 2 shall be
clipped.

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SIST EN 60961:1999

961 ©IEC:1993 29 -
-
Table 2 - Amplitude clipping (luminance)
525 line-60 field 625 line-50 field
MODEI MODE II MODEI MODE II
+250 % +260 % +250 % +300 %
Nominal
Positive excursion limit
Maximum +255 % +265 % +255 % +305 %
-65 % -100 % -65 % -150%
Nominal
Negative excursion limit
Maximum -70 % -105 % -70 % -155 %
11.1.6
Recorded carrier frequency
Carrier frequency corresponding to reference levels of the modified luminance signal shall
be as defined in table 3.
Table 3 - Recorded carrier frequency (luminance)
525 line-60 field system MODE I MODE II
7,7 MHz
Peak white 6,5 MHz
50 % level 5,7 MHz 7,0 MHz
6,27 MHz ± 0,05 MHz
Blanking 4,97 MHz ± 0,05 MHz
5,7 MHz
Synchronization tip 4,4 MHz
Frequency deviation 1,43 MHz ± 0,05 MHz 1,43 MHz ± 0,05 MHz
625 line-50 field system MODE I MODE II
8,8 MHz
Peak white 6,4 MHz
8,1 MHz
50 % level 5,7 MHz
Blanking 5,00 MHz ± 0,05 MHz 7,40 MHz ± 0,05 MHz
6,8 MHz
Synchronization tip 4,4 MHz
Frequency deviation 1,40 MHz ± 0,05 MHz 1,40 MHz ± 0,05 MHz
NOTE - Frequency deviation is between peak white and blanking level.
11.1.7 Record head current
11.1.7.1 The amplitude of the recording current for the Y track shall be such that a
maximum level of remaining flux on tape is produced when recording a Y signal with a
50 % average picture-level.
11.1.7.2 The amplitude of the Y track record current shall decrease with increasing
frequency in the range 2 MHz to 10 MHz according to a straight line contained within limit
lines as shown in figure 11.
This method assures optimum recording irrespective of video head material.

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SIST EN 60961:1999
961 © I EC:1993 – 31 –
11.2
Chrominance channel
11.2.1 Signal processing
A signal processing system as specified in this clause shall contain in the order of the
signal flow the following elements.
11.2.1.1 A means of compressing the time scale of the R-Y and B-Y signals over a period
of one horizontal line such that they may be time multiplexed into one horizontal line.
11.2.1.2 A means of adding a horizontal timing pulse.
11.2.1.3 A video detail enhancement process.
11.2.1.4 A video pre-emphasis network.
11.2.1.5 A means of clipping the video signal after pre-emphasis.
11.2.1.6 A linear frequency modulator having constant deviation with respect to the
amplitude of the modulating frequencies.
11.2.1.7 A high pass filter to reduce the amplitude of the low-frequency components of
the FM chrominance signal.
11.2.1.8
A means of combining the frequency-modulated audio signal, and the
frequency-modulated chrominance signal in MODE II when the FM audio signals are
present.
11.2.1.9 An amplifier of the frequency-modulated carrier signal to provide alternating
current drive to the C channel recording heads.
11.2.2 Time compression and multiplexing
11.2.2.1 The R-Y and B-Y signals shall each be compressed into a half time scale. The
starting point of compression shall be as shown in figures 7a and 7b.
11.2.2.2 The compressed R-Y and B-Y signals shall be multiplexed alternately as
shown in figure
8.
11.2.2.3 The compressed and multiplexed R-Y and B-Y signals shall be delayed by one
horizontal line with respect to the luminance signal.
11.2.3 Addition of a horizontal timing pulse
A horizontal timing pulse shall be added to the compressed and multiplexed R-Y and B-Y
signals as shown in figures 7a and 7b. The fall time of the timing pulse shall have an
approximate Gaussian shape with a fall time of 220 ns.
11.2.4 Chrominance detail enhancement
The video signal shall receive detail enhancement with the characteristics shown in
table 1.

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SIST EN 60961:1999
961 ©IEC:1993 - 33 -
11.2.5
Chrominance pre-emphasis
The pre-emphasis is defined by the frequency and phase characteristics of the network
as shown in figure 6, when fed from a zero impedance source and feeding an infinite
impedance load.
11.2.6 Amplitude clipping
For a signal with timing pulse tip at -105 % and nominal positive peak at +50 % corre-
sponding with "100/7,5/77/7,5 colour bars" of the 525 line-60 field system, or at -120 %
and nominal positive peak at +50 % corresponding with "100/0/75/0 colour bars" of the
625 line-50 field system, any positive or negative amplitude excursions exceeding the le-
vels shown in table 4 shall be clipped.
Table 4 - Amplitude clipping (chrominance)
525 line-60 field 625 line-50 field
MODEI MODE II MODE I MODE II
Nominal +175 % +230 % +175 % +260 %
Positive excursion limit
Maximum +180 % +235 % +180 % +265 %
Nominal —305 % —305 % —300 % —380%
Negative excursion limit
% —310 % —305 % —385 %
Maximum —310
11.2.7
Recorded carrier frequency
Carrier frequencies corresponding to reference levels of the compressed colour difference
signal shall be as defined in table 5.
Table 5 - Recorded carrier frequency (chrominance)
525 line-60 field system MODE I MODE II
(100/7,5/77/7,5 colour bars)
Peak positive video excursion 4,0 MHz 4,8 MHz
Peak negative video excursion 5,0 MHz 5,8 MHz
Blanking 4,5 MHz ± 0,05 MHz 5,3 MHz ± 0,05 MHz
Timing pulse tip 5,55 MHz 6,35 MHz
Frequency deviation 1,0 MHz ± 0,05 MHz 1,0 MHz ± 0,05 MHz
625 line-50 field system MODE I MODE II
(100/0/75/0 colour bars)
5,6 MHz
Peak positive video excursion 4,0 MHz
Peak negative video excursion 5,0 MHz 6,6 MHz
Blanking 4,5 MHz ± 0,05 MHz 6,1 MHz ± 0,05 MHz
Timing pulse tip 5,70 MHz 7,3 MHz
Frequency deviation 1,0 MHz ± 0,05 MHz 1,0 MHz ± 0,05 MHz
NOTE — Frequency deviation is between peak positive and negative video excursions.

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SIST EN 60961:1999
961 ©IEC:1993 – 35 –
11.2.8
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