Quantum DLT 2000 Handbook page 52

Figure 4-4 DLT 7000/DLT 8000 Read/Write Head
back and forth to record at highest data density, yet it can still read
older formats by assuming vertical position shown here.
tapes. You will never need most of them. But if you do need some old
tapes from last year, or 5 years ago, or just last week, you would have
a major problem if you had changed backup platforms. That is gen-
erally not the case with DLTtape technology. A cartridge recorded on
a DLT 2000 drive three or four years ago can be read on a DLT 4000
drive today. You can put a DLTtape IV cartridge in a DLT 4000 drive
today, fill it with data, and two years from now you will be able to
read it on a DLT 8000 drive (see Figures 4-5 and 4-6). All DLTtape
drives up to the DLT 4000 drive use a similar head design and record-
ing pattern that makes possible compatibility among drives.
However, the DLT 7000 and DLT 8000 drives use a new recording
pattern, Symmetric Phase Recording. The read/write head of the
DLT 7000 and DLT 8000 drives tilt forward and back (see Figure 4-5)
to achieve higher track density. When a DLTtape cartridge that has
been recorded on a DLT 4000 drive, for example, is inserted in a
DLT 8000 drive, the drive automatically detects the difference in
recording pattern. The DLT 8000 drive then automatically adjusts its
read/write head (Figure 4-6) to a vertical position that enables it to
read the older DLTtape cartridge.
4.10 WHY CUSTOMERS WANT DLTtape SYSTEMS
Forward Reverse
Write Cores Write Cores
Reader Cores
tilts