In addition to lateral parity, many units use a
longitudinal parity check. A special check frame is
written after the last data frame of each record. This
frame, as shown in figure 9-10, contains the parity bits
for the sum of all the ONES written in each track. In
other words, each bit of the check frame is a parity bit
for that track of data. Longitudinal parity checks help
identify errors to the specific track or bit position on
tape.
TOPIC 2—MAGNETIC TAPE
DEVICES
Magnetic tape storage devices can be divided into
two functional areas, as shown in figure 9-12:
l Magnetic tape control or controller
l Tape transport
Now let’s take a look at a typical magnetic tape unit
and its associated tape transport. This unit is based on
the RD-358(V)/UYK Magnetic Tape Unit, but is a
compilation of several tape units. Specifications used
at your command and are intended only to help you get
a more detailed understanding of the electronic and
electromechanical nature of magnetic tape units.
The magnetic tape unit (MTU), shown in figure
9-13, provides auxiliary (secondary) data storage for
one or two computers (duplex operation). The tape unit
is used primarily for operational and maintenance
program loading for the combat direction system
(CDS). It is also used to record real-time data extracted
from the CDS, to copy maintenance and operational
program tapes, and to patch or modify maintenance and
operational program tapes.
This MTU can control up to four magnetic tape
transports (MTTs). Standard shipboard configurations
consist of two or four transport units. The MTTs use
0.5-inch, A-wound (oxide coating on the underside of
the tape as it is wound on the reel), polyester-based
magnetic tape wound on industry standard open reels.
The MTTs are single-capstan, vacuum-column tape
may or may not be the same as the magnetic tape unit
drives as shown in figure 9-14.
Figure 9-14.—A magnetic tape transport.
9-11
