Method of and device for determining the total playing time of a tape

摘要: A method of and a device for determining the total playing time magnetic tape accommodated in cassette (1) magnetic-tape recording and/or reproducing apparatus, example video recorder helical-scan type. The (4) is moved between spool coupled to first reel disc (2) second (3), two measurements being carried out. In measurement with known speed. revolution times (Tl, Tr) are measured this parameter derived which corresponds sum squares times. cassette-specific constant (β) from during N revolutions one discs each disc. For ratio K(n) calculated thus determined constant, proportional L(n)/Lt Lt length L(n) either already used or residual tape, where n an integer 1 « N. approximation ratios approximated by at least quadratic function dependence on (K(n) = X + A.n B.n2 ...) obtained.