Handbook

Head Guide Assembly
Probably the most important new feature introduced with the
TF85 was the patented six-roller head guide assembly (HGA). This
mechanism provides a gentle, solid path to precisely move the tape
past the read/write head. This boomerang-shaped assembly con-
sists of a forged aluminum base with six precision rollers fixed to
it. The new HGA enabled the engineers to safely increase track
density from 48 tracks to 128 tracks across the half-inch wide tape.
The six-roller head guide assembly (see Figure 3-1) gave the TF85
a much shorter tape path than helical scan systems like the 8mm
drive,which meant less wear and tear on the tape.The rock solid
platform of the HGA also provided the industry’s most accurate
tape path. Helical scan systems have to draw tape around a spin-
ning read/write drum, which requires a moving tape path with
many more parts and points of tape wear.
Write/Read/Write
Another innovation in the TF85 resulted in high performance data
transfer speed and improved error correction.The read/write head
was equipped with an additional write element. The elements now
were arranged in a write/read/write pattern, allowing continuous
accuracy checking. This pattern enabled the TF85 to read after
writing on two channels and in both forward and reverse. Multi-
channel serpentine recording was born.
Seven-Cartridge Autoloader
To meet the need for unattended backup of large databases, Digital
also introduced a seven-cartridge autoloader, designated the TF857.
This system used a single TF85 drive, a seven-cartridge magazine,
and an elevator mechanism. Tape loaders and libraries minimized or
eliminated operator involvement and simplified tape management.
HISTORY OF DLTtape TECHNOLOGY3.4