Sunday, September 5, 2010

Tape leaders

In most compact cassettes the magnetic tape was attached to each spool with a leader, usually made of strong plastic (see right-hand image). This leader protected the weaker magnetic tape from the shock occurring when the tape reached the end. Leaders can be complex: a plastic slide-in wedge anchors a short fully-opaque plastic tape to the take-up hub; one or more tinted partly-opaque plastic segments follow; the clear leader (a tintless partly opaque plastic segment) follows that wraps almost all the way around the supply reel before splicing to the magnetic tape itself. The clear leader spreads the shock load to a long stretch of tape instead of to the microscopic splice. Various patents have been issued detailing leader construction and associated tape player mechanisms to detect leaders.[26] Cassette tape users would also use spare leaders to repair broken tapes.[27]

The disadvantage with tape leaders was that the sound recording or playback did not start at the beginning of the tape, forcing the user to cue forward to the start of the magnetic section. For certain applications such as dictation special cassettes containing leaderless tapes were made, typically with stronger material and for use in machines which had more sophisticated end of tape prediction.

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