1、 STD-SMPTE 238M-ENGL 1998 8357403 0003435 197 SMPTE STANDARD for Television Analog Recording - 1 /2-h Type L - Tapes and Cassettes SMPTE 238M-1998 Revision of ANSVSMPTE 23EM-1992 1 Scope This standard specifies the magnetic tapes and video cassettes for the 1/2-in type L helical-scan video tape reco
2、rder system. 2 Test conditions 2.1 Tests and measurements shall be made under the following conditions unless otherwise stated: -Temperature 20C IC 1 “C - Relative humidity (50k 2)% - Stabilization time 24 hours 2.2 Dimensions shall be as specified in the figures and tables (see annex B). 3 Mechanic
3、al characteristics of video cassettes 3.1 Outside dimensions 3.1.1 shown in table 1. Two cassette sizes shall be identified as Table 1 - Cassette identification Outside Model dimensions (mm) Figures 1 O to 18 S - Small cassette L - Large cassette 145 x 254 x 25 NOTE - For purposes of drawing clarity
4、, the S cassette shell is represented as two different shells - oxide tape and metal-particle tape shells. It is the manufacturers choice to manufacture single Page 1 of 19 pages 3.2 Datum planes 3.2.1 Datum plane 2 is determined by three datum spots, A, B, and C, as indicated in figures 3A and 12A.
5、 3.2.2 Datum plane X shall be orthogonal to datum plane 2 and include the center of datum holes (a) and (b), as shown in figures 2A/2B and 11. 3.2.3 Datum plane Y shall be orthogonal to both datum planes X and Z and include the center of datum hole (a), as shown in figures 2N2B and 11. 3.3 Window ar
6、ea and label area The crosshatched areas in figures 1NlB and 10, defined as the IabeVwindow area, shall not protrude beyond the height of the cassette surface. 3.4 Manufacturers identification holes Three manufacturers holes, referred to as recognition holes, shall be provided (refer to figures 2N2B
7、 and 11). 3.4.1 Tape type identification hole Hole one shall identify the tape type within the cas- sette. The detected state “1 “ shall indicate metal-oxide tape; detected state “O“ shall indicate metal-particle tape. Detection of tape type by the machine shall determine mode 1 or mode 2 operation.
8、 3.4.2 Tape thickness identification hole Hole two shall identify tape thickness. Detected state “1 “ shall identify 20 pm tape; detected state “O“ shall identify 15 pm tape. Copyright O 1998 by THE SOCIEPI OF MOTION PICTURE AND TELEVISION ENGINEERS 595 W. Hamdale Ave., White Plains, NY 10607 (914)
9、761-1100 Approved December 7,1998 STD-SMPTE 238M-ENGL 3778 8357403 000343b 023 SMPTE 238M-1998 3.4.3 Reel hub diameter identification hole Hole three shall identify the reei hub diameter. De- tected state “1“ shall identify a small hub; detected state “O shall identify a large hub (see figures 6 and
10、 15 for details concerning usage). 3.5 Safety tab and plug 3.5.1 Usage Use of the safety tab (for oxide) and safety plug (for metal) is intended to activate or produce a record lock-out condition in the event the safety tab or plug is activated. 3.5.2 S cassette The S cassette may contain either oxi
11、de or metal- particle tape. When loaded with oxide tape, the safety tab (for oxide), as shown in figures 2A/2B, shall acti- vate the mode 1 record lock-out condition if the tab is removed. A hole 10 mm minimum deep from datum plane Z (CC in figures 2A/2B) defines the mechanical tolerances for the se
12、nsing device. When loaded with metal-particle tape, the safety tab (for oxide) shall be removed (preventing the record condition for machines capable of mode 1 operation). The safety plug defined by DD in figure 28 defines the mechanical tolerances for the sensing device. Detec- tion of no hole shal
13、l cause the record lock-out condi- tion for mode 2 to exist. 3.5.3 L cassette The L cassette contains only one safety plug. If the safety plug is removed, both mode 1 and mode 2 record lock-out is activated. Dimensions of the safety plug are shown in C-C of figure 11. The cassette may be loaded with
14、 either oxide or metal-particle tape. 3.5.4 Deformation The safety tab and plug shall not be deformed over 0.3 mm when a force of 2.0 N is applied, using a 2.5-mm diameter rod. 3.6 Reels 3.6.1 The dimensions of the reels shall be in accordance with those given in figures 6 and 15. 3.6.2 The reels sh
15、all be locked automatically when the cassette is ejected from the video tape recorder or player unit. 3.6.3 The reels shall be unlocked automatically when the cassette is inserted into the video tape recorder/player unit. The reel shall be com- pletely released when the cassette lid is opened 27.5 m
16、m or more from datum plane Z. 3.6.4 The reels in the cassette shall be pressed by the reel spring with a specified force under the conditions specified in figures 7 and 16. The reel spring shape shall conform to figure 7 for the S cassette and figure 16 for the L cassette. The spring force shall be
17、1.5 N k 0.5 N for the S cassette and 3.4 N f 0.5 N for the L cassette when the reel is depressed to 2.0 mm +0.2 mm - 0.1 mm above datum plane Z. 3.6.5 Dimensions specified in this standard apply to the cassette only; no transport dimensions should be derived from this standard. 3.7 Cassette lid 3.7.
18、1 The cassette shall be provided with a lid that is unlocked automatically when the cassette is inserted into the video tape recorder/player unit and locked automatically when the cassette is ejected. 3.7.2 The force needed to open the lid shall be 1.5 N or less (see figures 9 and 18). 3.7.3 The lid
19、 shall open 29.0 mm, as shown in figures 4 and 13, when the cassette is inserted into the video tape recorder/player unit. 3.7.4 The lid shall be unlocked when the lid lock lever is shifted in either direction A or B, as illustrated in figures 8 and 17. The force needed to unlock the lid shall not b
20、e greater than 1 N in the A direction and not greater than 1.5 N in the B direction. 4 Magnetic tape 4.1 Type The magnetic tape used for 1/2-in type L helical-scan video tape recorders shall be either oxide tape or metal-particle tape. Page 2 of 19 pages STD-SMPTE 238M-ENGL 1998 8357401 0003437 TbT
21、m 4.2 Base material The base material shall be polyester or its equivalent. 4.3 Tape width The width of the magnetic tape shall be 12.65 mm f 0.01 mm. 5 Leader and trailer tape 5.1 Mechanical characteristics SMPTE 238M-1998 The leader and trailer tape shall contain a metal foil providing conductivit
22、y per centimeter of more than 200 S (mho) so that the magnetic tape automatically stops running when this end is detected in the re- corder. 4.4 Tape thickness 5.2 Leader and trailer tape dimensions The thickness of the magnetic tape shall be as shown in table 2. 4.5 Coercivity Two levels of coerciv
23、ity shall be permitted: Class 720 tape (mode 1 operation) oxide; class 1500 tape (mode 2 operation) metal particle. 4.6 Transmissivity Transmissivity shall be less than 5% measured over the range of wavelengths 700 nm to 900 nm. 4.7 Offset yield strength 5.2.1 Tape width The width of the leader and
24、trailer tape shall be 12.65 mm 10.03 mm. 5.2.2 Tape thickness The thickness of the leader and trailer tape shall be less than 45 pm. 5.2.3 Tape length The length of the leader tape, Li, and the trailer tape, Lp, specified in figure 19, shall be as shown in table 3. The offset yield strength shall be
25、 greater than 19.6 N. 5.3 Offset yield strength 4.8 Residual elongation The residual elongation of the magnetic tape shall be less than O. 15%. (Test method: Apply a 13.9 N load to a 1 m long and 12.65 mm wide test tape for 10 minutes. Remove the load and measure the tape length after a 0.2 N load i
26、s applied continuously for another 1 O minutes.) 4.9 Magnetic orientation The offset yield strength of the leader and trailer tape shall be greater than 29.4 N. 5.4 Splicing break strength The spliced portion between the magnetic tape and the leader or trailer tape shall withstand a tension of 14.7
27、N. The magnetic particles shall be longitudinally ori- ented. Page 3 of 19 pages STD-SMPTE 238M-ENGL 1998 8357403 0003438 7Tb SMPTE 238M-lW 1n.l.1 I Max. 138.2 81:. I I ! L Min. 141.8 (6) Datum Plane x r Note 6 Safety DbUq TYDe NOTES 1 The dimensions are inspected by using limit gauges. 2 No part of
28、 the lid shall protrude beyond the bottom plane of the cassette during the opening and closing motion of the lid. 3 This dimension shall be specified from datum plane Z. 4 Label and/or window area is available for the label and/or window (crosshatched area). 5 The cassette may be held in position by
29、 the recorder and/or player unit on this holding area (hatched area). 6 The fine hatched area shows the acceptable range of the plug notch position and depth at the side when the plug is used. Figure IA - Appearance of video cassette top and side view (oxide tape S cassette) Page 4 of 19 pages STD-S
30、MPTE 238M-ENGL 17798 D 8357401 0003437 832 SMPTE 238M-1998 Min.l.1 !I+ _Min. 1.1 I1 T I I l e!:- I ! I Max.138.2 1- -(SI Min. 141.8 NOTES 1 The dimensions are inspected by using limit gauges. 2 No part of the lid shall protrude beyond the bottom plane of the cassette during the opening and closing m
31、otion of the lid. 3 This dimension shall be specified from datum plane 2. 4 Label and/or window area is available for the label andor window (crosshatched area). 5 The cassette may be held in position by the recorder andor player unit on this holding area (hatched area). 6 The fine hatched area show
32、s the acceptable range of the plug notch position and depth at the side when the plug is used. Figure 1B - Appearance of video cassette top and side view (metal tape S cassette) Page 5 of 19 pages STD*SflPTE 238M-ENGL 1978 8357403 O003440 55LI H SMPTE 238M-1998 O n.4.3 x.1.7 Datum Plane XI safety ta
33、b TYDe Detail of F -LM ax . o .5 Sect I on CC - sect i on BB sect ion AA Mi n. 9:; Sect ion BE sect ion sect ion CC M i n. 141.8 (6) Recogn i il 7 Detail of D sect ion FE le.2(TaDe thickness! hoLe.l(TaDe twe) tion hole.3(Reel hub dia) - 254fi.6 Note 1 . II I NOTES 1 The dimensions are inspected by u
34、sing limit gauges. 2 No part of the lid shall protrude beyond the bottom plane of the cassette during the opening and closing motion of the lid. 3 Label and/or window area is available for the label and/or window (crosshatched area). 4 The cassette may be held in position by the recorder and/or play
35、er unit on this holding area (hatched area). 5 The fine hatched area shows the acceptable range of the plug notch position and depth at the side when the plug is used. Figure 10 - Appearance of video cassette top and side view (oxide and metal L cassette) Page 12 of 19 pages SMPTE 238M-1998 section
36、HH Max I 7 Sect ion AA Sect ion BB Sect io1FF sect ion QQ Recognition hole.2(Tape thickness) / Recognition hole.l(TaDe type) / i Recognition nole.3(Reei hub dia) Detail of J sect ion KK Note 2 4-4 Datum Piane Y Detail of L NOTES 1 Datum hole (a) is primary. 2 The crosshatched area shows the VTR dete
37、ction area. Figure 11 - Appearance of video cassette bottom view (oxide and metal L cassette) Page 13 of 19 pages CMPTE 238M-lQ98 STD*SMPTE 238M-ENGL 3918 8357403 0003448 895 14 7fO.3 9010.3 Datum spot C Datum spot D r Y “I 12A - Datum spots and supported areas x direction Q Y direction NOTES 1 Datu
38、m spots shall be 10 mm in diameter. 2 The four crosshatched areas, which are supported areas, shall be coplanar within 0.05 mm of each datum spot. The four crosshatched areas shall be coplanar with the hatched area. 3 Datum plane 2 shall be determined by the three datum spots, A, B, and C. 4 Datum s
39、pot D shall be coplanar within 0.3 mm of datum plane Z. 5 Areas within 1 mm from the edge of the cassette shall not be used as supported areas. 6 Reel flange clearance, L: 15 mm. 7 Perpendicularity of tape guides (even if they are tapered) is specified as follows: Take-up side Of 0.15 mm Of 0.15 mm
40、12B - Tape guide X and Y are the coordinates of the projection of the upper center of tape guides on the plane which includes the lower center of tape guides as the origin and are parallel to datum plane 2. Figure 12 - Datum spots, supported areas and tape guides (L cassette) Page 14 of 19 pages STD
41、-SMFTE 230M-ENGL 1998 8357901 0003499 781 W SMPTE 238M-1998 i Lever for opening the lid Lever for oPenina the lid r.5+;.5 - Recording side% 178*0.5 i 3 I -Y- - -1 N u - LD In NOTES 1 Rotating direction during forward operation. 2 The opening range of the lid in the recorder and/or player unit is 27.
42、5 mm +1.5 mm -0 mm. Figure 13 - Location of cassette reels in the recorder and/or player (L cassette) I Datum Plane 2 Max.111.: J Mln.191 . Min. 127 Min.20.8,” Min. 131.5 - Sect I on M Datum Plane2 NOTES 1 The hatched area is where the loading mechanism of the video tape recorder and/or player unit
43、positions the video cassette 2 The hatched and crosshatched areas are so designed that the loading mechanism of the video tape recorder and/or player when it is inserted. unit unwinds and extends the magnetic tape toward the drum head after the lid opens. Figure 14 - Protecting lid of cassette (L ca
44、ssette) Page 15 of 19 pages STD-SMPTE 238M-ENGL 1998 83574133 0003450 LiT3 II SMPTE 238M-1998 530Min. 2 60M i n . Nominal recording timelHub diameter of feels1 053.3m.z rfm 036t0.2 mn NOTES 1 Recording time is specified for a tape speed of 11 8.582 mds. 2 Cassettes with playing time between 30 and 6
45、0 minutes are not available at present. Figure 15 - Reel of cassette (L cassette) 1125) supply side Take-up side Figure 16 - Height of reels upon rotation (L cassette) Page 16 of 19 pages STD*SMPTE 238M-ENGL 1778 E 8357401 0003451 33T SMPTE 238M-1998 I 1 I Datum Plane y, _ Di I .- II -1 , I. 5: P N
46、fl I ion B unlocking lever . .ection A 1 1 view c rn X % 2-Max . RD. 6 x ,“I LL F A Plane Z Arrow view C Note 1 Note 2 Arrow view D Note 1 Note 2 Section EE Note 1 Note 2 NOTES 1 The crosshatched and hatched areas show the allowable total area where the unlocking lever, extending from the video 2 Th
47、e crosshatched area shows the range of the unlocking lever insertion which permits the lid to be unlocked. 3 Allowable range within which the unlocking lever can be inserted in A direction. 4 Allowable range within which the unlocking lever can be inserted in B direction. 5 The tip of the unlocking
48、lever shall be shaped into a semicircle or hemisphere of which the radius is one half the unlocking tape recorder and/or player unit, can be inserted into a cassette. lever width. Figure 17 - Allowable and operating ranges for unlocking the cassette lid lever (L cassette) Page 17 of 19 pages Measur
49、ins ever / /Datum plane S cassette Figure 18 - Force needed to open the lid (L cassette) L cassette Table 2 - Tape thickness Nominal recording time (min) 5 Nominal Magnetic tape thickness (krn) recording time Magnetic tape thickness (pm) (min) Oxide tape Metai-particle tape Oxide tape Metal-particle tape 5 I t-e- 10 15 I 19.0 t021.0 I *I 19.0 to21.0 1 14.1 to 15.3 I 14.1 to 15.3 20 I 30 14.1 to 15.3 30 14.1 to 15.3 60 90 I Magnetic tope- It II Table 3 - Leader and trailer ta
