Method of and apparatus for indicating length and remaining recording

Abstract

A method and apparatus for indicating the type, such as in terms of overall recording capacity, and remaining recording capacity of a recording tape. The tape is transported at a predetermined speed from a supply reel to a take-up reel. The rotations of the respective reels are sensed and the rotational periods T.sub.s and T.sub.t of the supply and take-up reels, respectively, are determined. Based upon these determined rotational periods, predetermined characteristics, such as the overall recording capacity, of the recording tape are indicated, irrespective of the arbitrary amount of tape which, initially, is wound upon the take-up reel. For example, a set of characteristics is stored for each value of T.sub.s.sup.2 +T.sub.t.sup.2 ; and the one set which is associated with the determined value T.sub.s.sup.2 +T.sub.t.sup.2 is selected. Also, the determined rotational periods T.sub.s and T.sub.t are combined with certain of said characteristics to indicate the amount of tape which remains upon the supply reel when that amount initially is unknown. The latter operation is carried out in accordance with the expression T.sub.R =P/1+.alpha..sup. 2 -Q, wherein T.sub.R represents the recording capacity of the tape which remains on the supply reel, .alpha..sup.2 =(T.sub.t /T.sub.s).sup.2, and P and Q are constant values associated with the type of tape which is used and are determined by the diameter of the supply (or take-up) reel hub, the total length of recording tape, the thickness of the tape, and the speed at which the tape is driven.