1、BRITISH STANDARD BS 6502:1984 IEC 767:1983 Incorporating Amendment No. 1 Specification for Helical-scan video tape cassette system using12.65mm (0.5in) magnetic tape on type Beta format (Implementation of CENELEC HD461S1) UDC 621.397.61:621.798.11-52BS6502:1984 This British Standard, having been pre
2、pared under the directionof the Electronic Equipment Standards Committee,was published underthe authority of the BoardofBSI and comes into effecton 31May1984 BSI 01-2000 The following BSI references relate to the work on this standard: Committee reference EEL/22 Draft for comment 84/207 17 DC ISBN 0
3、 580 13862 3 Committees responsible for this BritishStandard The preparation of this British Standard was entrusted by the Electronic Equipment Standards Committee (EEL/-) to Technical Committee EEL/22 upon which the following bodies were represented: British Broadcasting Corporation British Radio a
4、nd Electronic Equipment Manufacturers Association Cinematograph Exhibitors Association of Great Britain and Ireland Council for Educational Technology for the United Kingdom Electronic Engineering Association Independent Television Companies Association Industrial Council for Educational and Trainin
5、g Technology Ltd. The following bodies were also represented in the drafting of the standard, through subcommittees and panels: Association of Professional Audio and Radio Consultants Association of Professional Recording Studios Limited Audio Engineering Society British Educational Equipment Associ
6、ation British Film and Television Producers Association British Kinematograph, Sound and Television Society British Photographic Association Educational Television Association Ergonomics Society European Tape Industry Association Independent Broadcasting Authority Music Trades Association Royal Phot
7、ographic Society Royal Television Society Amendments issued since publication Amd. No. Date of issue Comments 6417 November 1990 Indicated by a sideline in the marginBS6502:1984 BSI 01-2000 i Contents Page Committees responsible Inside front cover National foreword iii Section 1. General 1 Scope 1 2
8、 Object 1 3 Environment 1 Section 2. Video-tape cassette 4 Mechanical parameters 1 Section 3. Videocassette recorders 5 Tape speed 2 6 Drum diameter 2 7 Tape tension 3 8 Maximum forces and tensions 3 9 Automatic stop system 3 10 Video heads 3 11 Track configuration and dimensions 4 Section 4. Tape c
9、haracteristics 12 Dimensions of video tape 4 13 Leader tape and trailer tape 4 14 Magnetic tape properties 5 Section 5. Recording characteristics 15 FM recording of luminance component 5 16 NTSC chrominance signal recording 6 17 PAL chrominance signal recording 7 18 SECAM chrominance signal recordin
10、g 8 19 Time difference between the luminance and chrominance signals 10 20 Audio signal recording 10 21 Control signal recording 11 Appendix A Noise reduction 27 Figure 1 Appearance of video cassette. Top and side view 12 Figure 2 Appearance of video cassette. Bottom view 13 Figure 3 Datum spots and
11、 supported areas 14 Figure 4 Location of reels of the cassette in the recorder and/or player 14 Figure 5 Protecting lid of cassette 15 Figure 6 Reel of cassette 16 Figure 7 Relationship between reels and reel spindles 16 Figure 8 Allowable and operating ranges for unlocking the leverofcassettelid 17
12、 Figure 9 Force needed to unlock the lid 18 Figure 10 Force needed to open the lid 18 Figure 11 Spring force needed to hold the reel 18 Figure 12 Strength of safety tab 19 Figure 13 Extraction force and friction torque 19 Figure 14 Tape tension measurement 20 Figure 15 Track configuration and basic
13、design dimensions. (Viewfromrecording side) 21BS6502:1984 ii BSI 01-2000 Page Figure 16 Block diagram of recording NTSC colour video signal (example) 23 Figure 17 Block diagram of recording PAL colour video signal (example) 24 Figure 18 Block diagram of recording SECAM colour video signal (example)
14、25 Figure 19 Characteristic frequencies 26 Table I Track configuration 22 Publication referred to Inside back coverBS6502:1984 BSI 01-2000 iii National foreword This British Standard has been prepared under the direction of the ElectronicEquipment Standards Committee and is identical with IECPublica
15、tion767 “Helical-scan video tape cassette system using12.65mm(0.5in) magnetic tape on type beta format”, published in1983 bythe International Electrotechnical Commission (IEC). This British Standard isalso in agreement with Harmonization Document HD461S1, published by the European Committee for Elec
16、trotechnical Standardization (CENELEC). Terminology and conventions. The text of the International Standard has been approved as suitable for publication as a British Standard without deviation. Some terminology and certain conventions are not identical with those used in British Standards. A Britis
17、h Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Cross-reference International Standard Correspond
18、ing British Standard IEC 94-1:1981 BS 6288 Magnetic tape sound recording and reproducing systems Part 1:1982 Specification for general conditions and requirements (Identical) Summary of pages This document comprises a front cover, an inside front cover, pagesi to iv, pages1to28, an inside back cover
19、 and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.iv blankBS6502:1984 BSI 01-2000 1 Section 1. General 1 Scope This standard applies to magnetic video recording usin
20、g12.65mm (0.5in) tape cassettes on two-head helical-scan video cassette recorders and defines the basic beta-format video cassette systems. 2 Object This standard gives dimensional and other characteristics necessary to permit the interchangeability of recorded cassettes. The requirements given rela
21、te to the525 line-60 field and625 line-50 field systems. Three tape speeds,40mm/s,20mm/s and13.3mm/s, are available for the525 line-60 field systems. Tape speed18.7mm/s applies to625 line-50 field system. 3 Environment Tests and measurements made on the system to check the requirements of this stand
22、ard shall be carried out under the following conditions: Section 2. Video-tape cassette 4 Mechanical parameters 4.1 Datum planes Datum plane Z shall be determined by three datum spots A, B and C indicated in Figure 3, page14. Datum plane X shall be orthogonal to datum plane Z and include the centres
23、 of datum hole(a) and datum hole(b) as shown inFigure 2, page13. Datum plane Y shall be orthogonal to both datum plane X and datum plane Z and include the centre of datum hole(a) as shown inFigure 2, page13. 4.2 Dimensions of cassette The dimensions permitting the interchangeability of cassettes sha
24、ll be in accordance withFigure 1 toFigure 12, pages12 to19. 4.3 Tape winding The recording side of the tape shall face outside on both the supply reel and take-up reel as shown in Figure 4, page14. 4.4 Label and/or window area The cross-hatched area inFigure 1 is available for the label and/or windo
25、w. The label as well as the window shall not protrude beyond the height of the cassette. 4.5 Cassette supporting areas The cassette shall be supported by the recorder and/or player unit on the hatched and cross-hatched area indicated inFigure 3. 4.6 Cassette holding areas The cassette shall be held
26、in position by the recorder and/or player unit on the holding area as described inFigure 1. 4.7 Guiding grooves The cassette shall be provided with three guiding grooves for correct insertion as shown inFigure 1 andFigure 2. Temperature: 20 1 C Relative humidity: 50 2% Barometric pressure: 86 kPa to
27、106kPaBS6502:1984 2 BSI 01-2000 4.8 Safety tab The cassette shall be provided with a safety tab as shown inFigure 2. The tab when broken out prevents accidental erasure. The tab shall be so constructed that it can withstand a force of0.6N using a rod of2.5mm diameter centred on the safety tab as sho
28、wn inFigure 12, page19. 4.9 Protecting lid 4.9.1 Automatic locking The cassette shall be provided with a lid that is automatically unlocked upon insertion into the recorder and/or player unit and automatically locked upon ejection from it. 4.9.2 Force to unlock the lid The lid can be unlocked by mak
29、ing the unlocking lever activate in either direction A or direction B, as illustrated inFigure 9, page18. The force needed to unlock the lid shall be not greater than1N in the A direction and not greater than1.5N in the B direction. 4.9.3 Force to open the lid The maximum force needed to open the li
30、d shall be not greater than1.5N as specified inFigure 10, page18. 4.9.4 Opening range The opening range of the lid in the recorder and/or player unit shall be within 27.5 mm. 4.9.5 Allowable and operating ranges for unlocking the lever of cassette lid The allowable range for unlocking the lever of t
31、he cassette lid is specified inFigure 8, page17, as shown by the hatched and cross-hatched areas, while the cross-hatched areas specify the operation range for it. 4.10 Reels 4.10.1 Locking of reels The reels shall be locked in order to avoid loosening of the tape during storage or transportation. U
32、pon opening the lid, specified in Sub-clause4.9, the reels shall be automatically unlocked. 4.10.2 Reel spring The reels in the cassette shall be pushed down by the reel spring with a force of1.5 0.5N as specified inFigure 11, page18. 4.11 Extraction force (F1, F2) With a holdback torque of0.001N.m
33、applied to a nearly empty reel, the amount of force required to pull the tape out from the reel shall not exceed0.17N. This shall apply to both supply and take-up reels of the cassettes as shown inFigure 13a, page19. 4.12 Friction torque of the take-up reel With a holdback tension of0.3N applied to
34、the nearly full take-up reel, the required torque to wind the tape shall not exceed0.015N.m as shown inFigure 13b, page19. Section 3. Videocassette recorders 5 Tape speed The video tape speeds shall be as follows: 6 Drum diameter The drum diameter shall be74.487 0.010mm. 525 line-60 field 625 line-5
35、0 field 40.0 mm/s 0.5% 20.0 mm/s 0.5% 13.3 mm/s 0.5% 18.7 mm/s 0.5% +1.5 0BS6502:1984 BSI 01-2000 3 7 Tape tension The tape back tension for a full supply reel shall be0.45 0.05N measured at the entrance to the drum when the tape is pulled as shown inFigure 14, page20. The ratio of tensions between
36、the maximum and minimum tape diameters shall be set as follows: 8 Maximum forces and tensions The machine shall not apply forces greater than the following: The maximum force on the safety tab described in Sub-clause4.8 shall be not greater than0.6N. The maximum tension on the splicing portion shall
37、 be not greater than10N. Maximum tension to the portions where the leader and trailer tapes are fixed on the reel hubs shall be not greater than15N. 9 Automatic stop system The tape transport shall have a mechanism which ensures that a non-contact automatic stopping device of the machine functions p
38、roperly at both ends of the magnetic tape through the effect of the leader tape and trailer tape as specified in Clause13. 10 Video heads 10.1 Inclined azimuth angle The gap line of video heads shall be slanted in accordance with the figure below. 10.2 Video head position on the drum The relative po
39、sition of head A to head B is defined in the following figure and table. 525 line-60 field 625 line-50 field 0 (nominal) 17 17 (nominal) NOTEThe angle 17 17 corresponds to the time-delay of95H. H:the nominal horizontal interval.BS6502:1984 4 BSI 01-2000 11 Track configuration and dimensions 11.1 Rec
40、ord locations The track configuration and dimensions shall be in accordance withFigure 15, page21, andTable I. The lower edge of the magnetic tape shall be the reference edge of tape. 11.2 Switching position and video signal overlap The switching position between the two video heads shall lie betwee
41、n five and nine horizontal lines before the front edge of the vertical synchronizing pulse. The minimum overlap of the two video heads shall be2.5 horizontal lines on either side of the switching position. 11.3 Relations of video track and video signal field The track used for the first field of the
42、 recorded video signal is not specified. However, recorders which can distinguish between fields shall record the first field on track A. Section 4. Tape characteristics 12 Dimensions of video tape 12.1 Magnetic tape thickness The maximum allowable thickness of the magnetic tape, including the coati
43、ng, shall be25.04m. 12.2 Magnetic tape width The width of the magnetic tape shall be12.65 0.02mm. 13 Leader tape and trailer tape 13.1 Automatic stop The leader tape and trailer tape of the width and thickness specified in Sub-clauses13.2 and13.3 shall contain a metal foil providing a conductivity p
44、er centimetre of more than200S (see Clause9). 13.2 Dimensions of leader tape and trailer tape The maximum allowable thickness of the leader tape and trailer tape shall be454m. The width of the leader tape and trailer tape shall be12.65 0.03mm. The length of the exterior part of leader tape for the c
45、ompletely empty take-up reel shall be250 60mm and that of the trailer tape for the completely empty supply reel shall be 70 mm (see figure below). Leader tape and trailer tape yield strength shall be30N or more. +10 20BS6502:1984 BSI 01-2000 5 13.3 Splicing The spliced portion shall withstand a tens
46、ion of15N. The attachment of the leader tape and trailer tape to the hub shall be capable of withstanding a force of20N. 14 Magnetic tape properties 14.1 Magnetic orientation The magnetic coating shall be longitudinally oriented. 14.2 Coercivity The coercivity shall be approximately44 10 3A/m to60 1
47、0 3A/m. 14.3 Yield strength The yield strength shall be 20 N or more. Section 5. Recording characteristics 15 FM recording of luminance component (seeFigure 16,Figure 17 and Figure 18, pages23,24 and25) 15.1 Low-pass filter The luminance component of the composite video signal shall be separated by
48、a filter system. The chrominance component of the composite video signal shall decrease by26dB or more at the colour subcarrier frequency (fsc) and by15dB or more within the range of fsc 0.5MHz after passing this filter system. 15.2 Pre-emphasis Response characteristics in the case of a tape speed o
49、f40mm/s for525 line-60 field. Response characteristics in the case of the tape speeds of20mm/s and13.3mm/s for525 line-60 field. Response characteristics in the case of625 line-50 field. Frequency 50 kHz 100 kHz 200 kHz 500 kHz 1 MHz 2 MHz 4 MHz Response 0.3 0.06 1.1 0.2 3.2 0.5 8.3 0.7 11.9 0.8 13.9 0.8 14.6 0.8 Unit: decibels. Input level(dB) Frequency 50 kHz 200 kHz 500 kHz 1 MHz 2 MHz 4 MHz 17 1.9 0.4 7.4 0.8 13.4 1.4 19.1 2.2 22.3 2.5 17.9 2.5 14 1.9 0.4 7.4 0.8 13.4 1.4 18.3
