Tape cartridge data storage library system

A method of recovering from jams in a library apparatus having a plurality of storage locations for retaining cartridges each having an end and having data stored thereon for interfacing with data exchanging apparatus at a station wherein the cartridges are moved from the storage locations into the station by operation of an arm extendable from the station and wherein the storage locations and station are movable relative to one another on command comprising the steps of

• detecting that relative motion has not occurred between the station and the storage locations despite issuance of a first movement command,
• motivating the library apparatus so that the end of any cartridge in the storage location facing the station is in alignment with the extendable arm, and
• moving the arm in an outward direction in order to provide a means for moving any cartridge jammed between the station and storage locations into one of the storage locations.

In a tape cartridge library system employing a rotatable carousel having a plurality of open slots each capable of receiving and storing tape cartridges with the carousel movable with respect to a station for performing data exchanging operations in conjunction with the cartridges on the carousel, apparatus for detecting whether cartridges are present in the positions on the carousel comprising

• an assembly including a first wall extending around said carousel open slots and a second wall secured to said first wall and extending therefrom to a position in proximity to the station on the opposite side of said carousel open slots, and
• detector means having a pair of elements communicating via a light beam in a line between said first wall and said station for detecting whether a cartridge is present in said open slot whenever said open slot is longitudinally aligned with said detector means communicating line with said pair of elements including a light source and a photocell.