A cassette has supply and take up reels with corresponding annular gears thereon. A pivotally mounted driving brake arm has an intermediately positioned pawl engaging the take up reel gear. An end of the driving brake arm is spaced from a coacting end of a pivotally mounted driven brake arm. An opposite end of the driven brake arm has a pawl for engaging the gear of the supply reel. When the tape is slack, the tape up reel incrementally rotates to tighten it, causing the take up reel pawl to incremental ratchet over the mating gear. This causes the driving arm to rotate and displace its end into abutting relation with the coacting end of the driven arm. Consequently, the ratchet of the driven brake arm rotates and its corresponding pawl disengages from the supply reel gear to allow the supply reel to incrementally pay out a length of tape sufficient to prevent overtightening.