MagTek InSpec 9000-2005 - Manual (Page 55)

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APPENDIX A. MAGNETIC ENCODING
This Magnetic Encoding Primer is intended to provide the reader with a basic understanding of
magnetic stripe cards and magnetic encoding. The subject of magnetic stripe encoding involves
many technical parameters that are often complicated and confusing. We will attempt to bring
these parameters into perspective as we discuss basic magnetism, how encoding and reading
heads work and the important aspects of magnetic media construction. First, we'll start with a
brief history lesson.
HISTORICAL BACKGROUND
Magnetic recording technology began in the late 1800's. Many scientists, throughout the next
half century, whose field involved electricity or magnetism, discovered the fundamentals that
magnetic stripe cards rely on today.
At the Paris Worlds Fair in 1900, Valdemar Poulsen demonstrated a magnetic wire recording
device. This device permitted voices to be recorded on an iron wire for later playback. Similar
devices were used aboard German submarines during the first World War as a means to transmit
secret voice information by recording the message at normal speed and then transmitting the play
back recording in reverse at higher speeds.
In 1928, a German patent was filed on a coating of iron particles on a strip of paper as a
recording medium and a machine that used such a strip. The German Magnetophone was
exhibited in Berlin in 1935.
After World War II, rapid growth in magnetic tape and recording occurred. Minnesota Mining
& Manufacturing (3M) started delivering iron oxide tapes in 1947, while Ampex began
delivering sound or "audio" recorders in 1948.
Meanwhile, a breakthrough in calculating machines came in 1944 when at Harvard University an
electromechanical calculator was developed that utilized binary arithmetic. "Binary" refers to a
counting method that only has two states; ON and OFF or in terms of numbers ONE and ZERO.
In 1951, the first commercial computer, UNIVAC I, was produced. Computers soon began to
utilize the memory storage ability of magnetic tape. Since computers function by manipulating
ONE bits and ZERO bits, only these two states needed to be stored. The technology of "digital"
recording was born. While the digital method of recording was similar to audio recording, it
differed in the amount of drive current used in the recording head. Audio recording relies on
varying the amplitude of the desired "signal", in order to reproduce both loud and quiet passages
as occurs in music. Digital recording relies on an even amount of signal amplitude. By
"saturating" the magnetic tape, the resulting signal amplitude remains fairly constant. This is a
key concept for our later discussion of how cards are recorded and read back.