Patent ID: 7016152

Claim:
A magnetic tape cartridge comprising: a cartridge casing and a single reel around which a magnetic tape is wound and which is contained in the cartridge casing for rotation, said cartridge casing is provided with a tape outlet opening for extracting the magnetic tape, and said tape outlet opening is provided with an opening and closing slide door, wherein said slide door is provided with an opener portion that abuts against a door opening member of a record and playback apparatus to move said slide door in the opening direction when said tape cartridge is placed in said record and playback apparatus, and a through-hole in a wall of said casing that serves as an engaging hole through which a projecting-type locking member, provided with a warping portion, is inserted and engaged from inside the cartridge casing to lock the slide door in the closed state, and wherein when an unlocking member is inserted into the engaging hole from outside the cartridge casing said unlocking member transforms said warping portion through the projecting-type locking member, whereby the projecting-type locking member is moved to an unlocked position.