Dat Technology Overview; Helical Scan Recording; Figure 3. External Dds Drive - Seagate STD124000N Product Manual

Chapter 1

DAT Technology Overview

Helical Scan Recording

Page 6

Figure 3. External DDS Drive

Developed for the audio electronics market, DAT technology was first applied in
computer peripherals in the late 1980s. Unlike traditional magnetic tape audio
cartridge products, DAT technology proves inherently reliable through the helical
scan recording method, which provides a high recording density with a very low
error rate. All DAT products, including computer implementations, use the helical
scan recording method. This recording method has been used in professional video
tape recorders (VTRs) since 1956 and in home video cartridge recorders (VCRs)
since 1974. In 1986, DAT products that used helical scan technology were first
developed for audio applications. DAT consumer products are specifically designed
for digital audio recording and playback.
Helical scan recording was originally developed as a method of efficiently recording
high-quality television signals on a relatively slow moving tape. It requires that both
the tape and the recording head move simultaneously. This recording method
results in an extremely high recording density, far higher than can be achieved with
stationary-head devices such as 1/2-inch open-reel or 1/4-inch cartridge tapes. (See
chapter 8, "Helical Scan Recording—Four-Head Design" for additional information.)
In helical scan recording, both the read and write heads are located on a rapidly
rotating cylinder or drum. The cylinder is tilted at an angle in relation to the vertical
axis of the tape. As the tape moves horizontally, it wraps around the part of the
circumference of the cylinder (102°) so that the head enters at one edge of the tape
and exits at the other edge before the tape unwraps.
Introduction
DAT Drives