Message Repeaters and Evacuation Systems 152740.6 Audio Archival
In addition to message repeating applications, there is a
need for long term storage—i.e., to preserve audio and
video data for future generations. It has been only the
last quarter century that we came out of the dark ages
and into the domain of digital storage, Table 40-1.
As the world is changing from analog to the digital
domain, the media for archiving must be improved.
After all, the medium used 20,000 years ago for written
information can still be read today, while today’s media
for audio storage lasts only a few years and playback
equipment becomes obsolete.
Today, most memory for audio storage is accom-
plished through solid state technologies. Solid state
technologies fall into four broad categories:
- Electrical memories based on semiconductor IC
technology. - Magnetic memories based on magnetic materials.
- Optical memories based on the interaction of light
with matter. - Molecular, chemical, or biological memory based on
changes in the atomic, molecular, or biological level.
Electrical memory is the most used technology for
digital audio storage. Information is stored in digital
form in various types of memory units. CommonTable 40-1. Evolution of Audio/Visual Information
Storage. Courtesy DIGIPRESS
Medium Origin
(year)Coding Access Lifetime
(years)Drawing/text:
Stone
Papyrus
Parchment
Ancient paper
Modern paper
Microfilm
Magnetic tape
Still image:
B&W film
Color film
Sound:
Cylinder
Mechanical disc
Magnetic tape
Optical disc
Moving images:
B&W film
Color film
Magnetic tape
Computer data
magnetic tape20,000 BC
3000 BC
200 BC
105 AD
1800 AD
1900 AD
1948 AD
1835 AD
1869 AD
1877 AD
1887 AD
1935 AD
1985 AD
1895 AD
1935 AD
1951 AD
1946 AD
1948 ADanalog
analog
analog
analog
analog
analog
digital
analog
analog
analog
analog
analog
digital
analog
analog
analog
analog
digital
projector
computer
player
player
player
player
player
player
projector
projector
player
computer100,000
5000
2000
1000
50
50
3
50
20
100
50
3
10
50
20
3
3