| 摘要 |
To provide a data store in which a data carrier (T) can hold a vast quantity of data and give rapid access, a format of parallel tracks is used each starting with a unique track identity number and a unique relationship to one or more longitudinal control tracks (B, C) which provide for high speed mode search, and low speed mode location, using video tape-recording servo-systems to surprising advantage. Coarse location of a required group of tracks may be provided by coded signal sequences on one control track (B1) and invididual tracks identified by coded signal sequence in a further longitudinal control track (B2). In one embodiment only the control track passes a reading head in the high speed mode, and in the slow mode the carrier is wound to half embrace a helical scanning drum carrying a plurality of heads. Read only devices may be provided for use as a reference source in library or computer installations possibly with multi-user and/or multi-bus facilities. Where required provision may be included for recording and/or read-out of stored data, but the control track sequence is preferably pre-recorded and constant. The data carrier can be in a preferred embodiment, a flexible tape in a cassette, but open reel-to-reel systems, short strips semi-rigid cards or rigid plates or drums can be used. The recording method can be magnetic or one of a variety of optical systems, and the data may be computer data, text, graphics video, or any combination thereof. |
