| 摘要 |
988,751. Magnetic tapes; preventing accidental erasure. AMPEX CORPORATION. June 13,1963 [June 29, 1962], No. 23670/63. Heading G5R. The tape 14 on a reel 12 can only be erased and/or recorded on when a highly permeable detachable magnetic ring 41 is snapped on to the reel to shunt, Figs. 2, 3, or to complete, Fig. 6, the effect of the field due to a bar-magnet 31 (31a) on a magnetic reed switch 29 whose contacts suitably activate the record/erase circuits. The contacts 32, 22 are reliliently biased to open circuit and in Figs. 2,3 are normally closed by the magnet 31 to short-circuit the means 27. The ring 41 shunts the field and the contacts spring open. In Fig. 6, the magnet 31a, the contracts and a highly permeable bar 52 form a U-shape open magnetic circuit only able to close the contacts when the circuit is magnetically bridged by the ring 41. The reel-hub 16, contains one or more captive grub-screws 47,which may be turned to their upward limit, as viewed in Fig. 5, after recording, to prevent the entry of a snap-fastener 49 on the ring 41. |
