Abstract: A tape transport cartridge is presented wherein the rotational kinetic energy of the two reels and tape packs are balanced, constant tension on a drive belt is effected by a counterbalanced idler roller assembly, and a temperature compensated brake acting on the drive belt contributes to achieving a stable tape pack over a wide temperature range.

Abstract: Long and short term variations in the speed at which a magnetic tape is moved with respect to a read and/or write head are minimized by maintaining the product of the speed of the tape payout and take-up reels constant. In accordance with a preferred embodiment the rotational speed of the payout reel and the rotational speed of the take-up reel are sensed and effectively multiplied to derive a signal which is compared with a predetermined constant magnitude reference signal. The result of the comparison is an error voltage which is employed to energize and thus control the speed of the drive motor for the take-up reel.