A device that is installed in a tape reel to permit writing on the tape. If a tape is mounted without the ring in position, writing cannot occur, the file is protected.

• 一种器件(实为一种塑料环)，将它装在磁带盘上便允许在磁带上写入数据。若没有套上此环，则不能写入数据，原磁带上的文件得到保护。