IEC 61904:2000 pdf download-Video recording – Helical-scan digital component video cassette recording format using 1 2,65 mm magnetic tape and incorporating data compression (Format digital-L).
2.1 .6 Guiding groove For correct insertion into the VTR, four guiding grooves for S cassettes as shown in figures 1 and 2, and three guiding grooves for L cassettes as shown in figure 1 5 shall be provided. 2.1 .7 Safety tab and safety plug For S cassettes, a safety plug at the supply reel side and a hole of minimum depth of 1 0 mm from datum plane Z at the take-up reel side shall be provided as shown in figure 2. For L cassettes, a safety plug shall be provided at the take-up reel side as shown in figure 1 5. 2.1 .8 Identification holes Five identification holes (holes 2 to 6) shall be located as specified in figures 2 and 1 5. There is no hole for hole 1 (tape type identification). There shall be two types of reel hub diameter: hole 3 closed: cassette with small hub; hole 3 open: cassette with large hub. Hole 2, hole 4 and hole 5 shall be closed and hole 6 shall be open. Other combinations are reserved for future assignment.
2.1 .9 Reel Locations of the reels, ready for rotation, are shown in figures 4 and 1 7. Dimensions of the reels are shown in figures 6 and 1 9. Heights of the reels are shown in figures 7 and 20. The reels shall be automatically unlocked when the cassette is inserted into the video tape recorder and/or player unit and automatically locked when the cassette is ejected from it. The reel shall be completely released when the cassette lid is opened 23,5 mm minimum from datum plane Z. The reels assembled in the cassette shall be pressed by the reel spring with a specified force under the conditions specified in figures 1 1 and 24. The reel spring shape is specified in figure 1 1 for S cassettes and in figure 24 for L cassettes, and the spring force shall be 1 ,5 N ± 0,5 N (1 53 gf ± 51 gf) for S cassettes and 3,5 N ± 0,5 N (357 gf ± 51 gf) for L cassettes when pressing on a reel 2,4 mm above datum plane Z as shown in figures 1 1 and 24. The force (F1 , F2) required to pull the tape out from the reel shall not exceed 0,1 7 N (1 7 gf), as specified in figures 1 3a and 26a. The torque required to wind the tape shall be less than 1 5 mN m (1 52 gf cm) for S cassettes and less than 30 mN m (305 gf cm) for L cassettes, as specified in figures 1 3b and 26b.