Quantum DLT 2000 Handbook page 60

tachometer also helps the system keep track of how much tape is
wound onto each reel and adjusts the speed of the two motors
accordingly. Each time a cartridge is loaded, the drive calculates
and sets the minimum tension required to achieve high-quality,
consistent read/write signals. This calibration system maintains
optimal-contact recording and helps extend the operational life of
the drive.
Self-Cleaning Head
Another important feature that helps extend tape life is the
DLTtape drive's self-cleaning head design. The write/read/write
elements on the head are aligned vertically on three tiny islands.
This reduces the point of contact with the tape recording surface
to a bare minimum. Along with the write/read/write islands, two
additional islands are included (see Figure 5-5). These extra two
Write Heads
Tape
Figure 5-5 Self-Cleaning Contoured Head
drives includes two fixed "outriggers" that wipe any debris from
tape, reducing head wear (top view of head).
5.6 RELIABILITY: THE HEART OF THE DLTtape SYSTEM
Write Heads
Read Heads
Outriggers
on DLTtape