What is MICR
What effects signal levels
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The
MICR font was developed by Stanford University in conjunction
with Bank of America and approved by the American Banking
Association. The font is known as the E-13B font. E-13B has
a total of 14 characters, ten specially designed numbers (0
through 9) and four special symbols (Transit, Amount, On-Us,
and Dash).
The letter "E" indicates the 5th
version considered. The letter "B" indicates the
2nd revision of that version. The number "13"
is derived from the 0.013 inch module construction used
for stroke and character width. This means that all character
widths, both horizontal and vertical, are in multiples of
0.013 inches ranging from 0.052 to 0.091. The significance
of this will be explained more thoroughly later in this
article.
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Figure
1. |
| MICR
Readers
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There
are three types of machines used to read MICR characters.
Two of these machines read the characters magnetically and
they are referred to as Magnetic Ink Character Recognition
(MICR) readers. The third machine is called an Optical Character
Recognition (OCR) reader.
E-13B characters are printed with toner containing iron oxide,
because it is capable of being magnetized. MICR readers transport
the checks containing the E-13B magnetic characters past a
magnet, thereby magnetizing the iron oxide particles. The
magnetized characters then pass under a magnetic read head.
The magnetic field (flux pattern) caused by the magnetized
characters generates a current in the read head. The strength
and timing of this current allows the reader to decipher the
characters.
There
are two types of magnetic readers: Single Track (single
gap or split scan) and Multiple Track (matrix or pattern)
readers.
Single
Track uses a read head with one gap to detect the magnetic
flux pattern generated by the MICR character. When a magnetized
E-13B printed character moves across the narrow gap of the
read head, the electric voltage caused by the magnetic flux
from the character generates a waveform unique to each character
(Figure 1).
The
Multiple Track reader employs a matrix of tiny, vertically
aligned read heads to detect the presence of the magnetic
flux pattern. The small individual read heads slice across
the character to detect the presence of magnetic flux. This
sensing of magnetic flux over time produces a unique matrix
pattern for each character (Figure 2).
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Figure
2. |
An
OCR reader does not use the magnetic properties to detect
the E-13B characters. Instead, it uses a scanner
to detect the amount of light reflected from the character
and the amount of light reflected from the background. A
photocell column detects the presence of the dark area of
a character (Figure 3).
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Figure
3. |
Waveform
Theory |
The
readers move and read documents from right-to-left. The
right-hand edge of the character, as a result, is the first
to cross the read head. Analysis of the signal level reading
of the character 0 will help explain this in greater detail
(Figure 4). As the character moves from left to right under
the read head, the gap detects the magnetism of the first
right-hand edge (edge 1). This results in the increase in
magnetism and a positive peak is created (peak 1). As soon
as the right-hand edge moves beyond the read head gap, no
new magnetism is found and thus the wave form returns to
the zero signal level.
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Figure
4. |
At
the second edge, the vertical read head detects a drop in
magnetism, which results in a -110 signal level at peak 2.
Again the waveform returns to zero until the next portion
of the inner ring of the character is detected. At this point
(peak 3), an increase in magnetism (+110) is indicated. Finally,
the outer portion of the character is read, resulting in a
negative peak (peak 4) of -130.
The placement of the vertical edges must
occur in increments of 0.013 inches from the first right
hand edge. There are five characters which have two positive
and two negative peaks similar to the character 0 and also
appear in a positive-negative-positive-negative format.
They are 0245 and the transit character. How are they then
differentiated from one another? By the horizontal location
of the peaks in the waveforms (see MICR magnetic footprint
in Figure 4). The peaks do require different amplitudes,
but ANSI standards allow them to vary from 50% to 200% of
the nominal amplitudes (Canadian standards allow them to
vary from 80% to 200% of the nominal amplitudes). This is
why the placement of the waveform is so important and why
the characters are shaped unusually.
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