Operator`s manual

Model VR240 Audio Logging Recorder
January 2000
B-1
APPENDIX B
4mm TAPE ISSUES
B-1. AVAILABILITY AND SELECTION.
VR240s equipped with 4mm tape drives are designed to use “Helical Scan 4mm Data
Cartridges” as a recording medium. These cartridges are colloquially and redundantly known as
DAT tapes (Digital Audio Tape tapes). It is important to understand the differences among the
tapes usable in the VR240. In some applications it may not matter which brand or quality you
use; in others it may be critical. We strongly recommend that you use only tapes marked DDS,
DDS-2, or DDS-3, depending on the types of drives installed in your VR240.
B-2. TAPE TYPES AVAILABLE.
The difference between DSS Data Cartridges and DAT tapes is primarily one of certified quality.
While the tapes are physically compatible and interchangeable, the Data Cartridges are certified
to have a limited number of defects and dropouts. DAT tapes primarily are used on audio
applications, which are not so demanding as data storage. Although the VR240 is an audio
logger, it logs the audio in data format. While it might be argued that a bad bit in the logged
data is of little significance, our hardware and the drive assemblies do not see it that way. As
described in Chapter 4, the drives employ error correction to make sure that there are no bad
bits. If the tape has a defect or dropout, the data is re-recorded until it is completely correct.
(And remember, we are also logging digital data, such as time, with the audio.)
If there is a dropout on the tape, it will not affect the data recorded, but it will waste tape. If
there are many dropouts, a lot of tape will be wasted. If the wasted tape exceeds the margins
built into the hardware and firmware, there will not be enough tape to record the full amount of
data expected, and loss of data may result.
B-3. SELECTING YOUR TAPE.
Your Tape selection will depend primarily upon your application. Please remember that you use
audio grade tapes essentially “at your own risk”. It has been our experience that their quality
varies significantly, both from manufacturer to manufacturer and lot to lot. The only time audio
grade tapes may be a good choice is when cost is of paramount importance and you know for
certain that you will change the tape long before it is expected to be full. Another risk incurred in
using audio or even non-approved data tapes is the possibility of oxide shedding and head
clogging. Particles shed from a poor quality tape can become lodged in the head assembly of
the drive and cause an increased error rate or even failure of the drive.
We therefore recommend data grade tapes in every case. While they are more costly, they will
give more reliable and predictable performance.