ISO 1004:1995
(Main)Information processing — Magnetic ink character recognition — Print specifications
Information processing — Magnetic ink character recognition — Print specifications
Cancels and replaces the second edition (1977). Specifies the shapes, dimensions and tolerances for the ten digits and four special symbols to be printed in magnetic ink and used für the purposes of character recognition. Describes the various types of printing defects and other printing considerations, together with the tolerances permitted, and also contains specifications for signal level measurement and references to Optical Character Recognition (OCR), a technology now often used in conjunction with E 13 B MICR reading.
Traitement de l'information — Reconnaissance des caractères à encre magnétique (MICR) — Spécifications d'impression
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Standards Content (Sample)
INTERNATIONAL Is0
STANDARD 1004
Third edition
1995-06-I 5
Information processing - Magnetic ink
character recognition - Print
specifications
- Reconnaissance des caractkres P encre
Traitemen t de I’in forma tion
- Spkcifica tions d ‘impression
magnktique (M/CR)
Reference number
IS0 1004:1995(E)
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IS0 1004:1995(E)
Page
Contents
Section I-Font E 13 B
1
..................................................
1 Scope
.................................... 1
2 Character configuration.
............................ 1
Character spacing and alignment.
3
..........................................
2
4 Character skew.
...................................... 2
5 Character tolerances.
3
Voids .
6
...................................... 3
7 Uniformity of ink film.
3
8 Extraneousink .
.................................. 4
9 Debossment (impression).
4
10 Signallevel .
8
11 Paper .
8
12 Format .
8
...................................
13 MICR ink performance.
Figures
.................. 9
Stroke 0 (Zero) to Stroke 3 (Three).
1to 4
.................. IO
5to 8 Stroke 4 (Four) to Stroke 7 (Seven)
.............. 11
9to 12 Stroke 8 (Eight) to Stroke 11 (Symbol 2)
......... 12
13 to 14 Stroke 12 (Symbol 3) to Stroke 13 (Symbol 4).
........................... 13
15 Character design matrix.
....................... 13
16 Distance between characters
13
...................
17 Allowable variation in vertical align
.......................... 14
Allowable character skew
18
14
....................................
19 Average edge
........................... 14
20 Average edge tolerance.
................................. 14
21 Edge irregularity.
15
..........................
22 Examples of single voids.
0 IS0 1995
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced
or utilized in any form or by any means, electronic or mechanical, tncluding photocopying and
microfilm, without permission in writing from the publisher.
International Organization for Standardization
Case Postale 56 l CH-1211 Geneve 20 l Switzerland
Printed in Switzerland
ii
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0 IS0 1995(E)
23 Examples of rows and columns . . . . .
..... 15
16
24 Restriction Areas for Extraneous Ink. .
....... 17
25 Waveform as it appears on face of oscilloscope:.
17
26 Signal peaks for calibrating all characters .
18
27 Ideal waveform peaks .
19
28 Secondary signal level document. .
29 Conductor arrangement for the wire card
20
calibration method. .
30 Test device suitable for generating magnetic flux
20
for the wire card calibration method. .
31 Distance of the right hand character from the right
21
hand reference edge .
Annexes
............................ 22
A Debossment and Linear amplifier.
23
B Equivalent metric-inch dimensions used in font E 13 B .
Figure
..................... 22
A.1 Circuit diagram of a typical linear amplifier.
Section 2 - Font CMC 7
Scope.2 4
14
24
15 Character configuration .
24
16 Means of automatic sensing. .
24
Reference edges of documents .
17
PrintLocation.2 5
18
Clearband.2 5
19
Character spacing and alignment. . 25
20
........................... 25
21 Character definition and tolerances
26
Extraneous ink (spots). .
22
26
Voids .
23
..2 6
Segment end zones .
24
Uniformity of ink. . 27
25
Debossment.2 7
26
Signal Level.2 7
27
27
Paper .
28
MICR inkpermanence.2 8
29
................................. 29
Symbols and abbreviations.
Figures
............................. 30
32 Format of documents.
................. 31
33 Magnified view of part of a character
Introduction to the drawings of the printed characters of
fontCMC7.3 2
Figures
33
Digits: Font height 3,20 mm (Hrl) .
34
Symbols: Font height 3,20 mm (I-frl) . 34
35
............. 35
36 Letters A to H: Font height 3,20 mm (Hn).
. . .
III
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IS0 1004:1995(E) 0 IS0
37 Letters I to Q: Font height 3,20 mm (&) . 36
38 Letters R to Z: Font height 3,20 mm (I-In). . 37
39 Digits: Font height 3,00 mm (&) . 38
40 Symbols: Font height 3,00 mm (Hf2) . 39
............. 40
41 Letters A to H: Font height 3,00 mm (Hf2)
42 Letters I to Q: Font height 3,00 mm (Hf2). . 41
43 Letters R to Z: Font height 3,00 mm (&) . 42
44 Digits: Font height 2,85 mm (Hfs) . 43
45 Symbols: Font height 2,85 mm (Hf3). . 44
46 Letters A to H: Font height 2,85 mm (Hf3) . 45
46
47 Letters I to Q: Font height 2,85 mm (Hf3) .
48 Letters R to Z: Font height 2,85 mm (Hf3) . 47
48
49 Digits: Font height 2,70 mm (Hf4) .
50 Symbols: Font height 2,70 mm (Hf4). . 49
51 Letters A to H: Font height 2,70 mm (Hf4) . 50
52 . 51
Letters I to Q: Font height 2,70 mm (Hf4)
53 Letters R to Z: Font height 2,70 mm (Hf4) . 52
54 The complete set of font CMC 7 characters. . 53
Annexes
C Equivalent metric-inch dimensions used in font CMC 7. . . 54
D Use of symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
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0 IS0
IS0 1004:1995(E)
Foreword
IS0 (the International Organization for Standardization) is a worldwide
federation of national standards bodies (IS0 member bodies). The work
of preparing International Standards is normally carried out through IS0
technical committees. Each member body interested in a subject for
which a technical committee has been established has the right to be
represented on that committee. International organizations, governmental
and non-governmental, in liaison with ISO, also take part in the work. IS0
collaborates closely with the International Electrotechnical Commission
(IEC) on all matters of electrotechnical standardization.
Draft International Standards adopted by the technical committees are
circulated to the member bodies for voting. Publication as an International
Standard requires approval by at least 75 % of the member bodies casting
a vote.
International Standard IS0 1004 was prepared by Technical Committee
ISOnC 68, Banking and related financial services, Subcommittee SC 2,
Operations and procedures.
This third edition cancels and replaces the second edition
(IS0 1004:1977), of which it constitutes a technical revision.
Annexes A to D of this International Standard are for information only.
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INTERNATIONAL STANDARD 0 IS0 Is,0 1004:1995 (E)
Information processing - Magnetic ink character
recognition - Print specifications
Section 1 - Font E 13 B
2.2 Dimensions
1 Scope
Detailed dimensions and the reference centre lines of
Section 1 of this International Standard specifies the
the printed characters for Strokes 0 to 13 are shown in
shapes, dimensions and tolerances for the ten digits
figures 1 to 14 inclusive. Figure 15 illustrates the charac-
and four special symbols to be printed in magnetic ink’
ter design matrix. Dimensions of the printed characters
and used for the purposes of character recognition. It
are as follows:
describes the various types of printing defects and
other printing considerations, together with the toler-
1) Character height
2,972 mm (0.117 in)
ances permitted, and also contains specifications for sig-
nal level measurement and references to Optical
2) character widths 1,321 mm (0.052 in)
Character Recognition (OCR), a technology now often
1,651 mm (0.065 in)
used in conjunction with E 13 B MICR reading.
1,981 mm (0.078 in)
The characters specified in section 1 of this Interna- 2,311 mm (0.091 in)
tional Standard were developed initially for use in banks
3) width of horizontal 0,330 mm (0.013 in)
to permit automatic document handling for bank data
and vertical bars
processing, but they have application to other automatic
processing systems as well.
4) minimum width of 0,279 mm (0.011 in)
horizontal bars (this
specification does
2 Character configuration
not apply to vertical
bars, see 5.5)
2.1 Designation
The series of standard magnetic ink characters consists 5) corner radii (except 0,165 mm (0.0065 in)
Stroke 0, see figure 1)
of ten digits and four special symbols. They are identi-
fied as follows:
6) tolerance (average + 0,038 mm (+ 0.0015 in)
Name Designation
edge)
Zero Stoke 0
One Stoke 1
3 Character spacing and alignment
Two Stoke 2
Three Stoke 3
3.1 Spacing of characters
Four Stoke 4
Five Stoke 5
3.1.1 Common fields (fixed format)
Six Stoke 6
Seven Stoke 7
3.1 .I.1 The distance between the right average edge
Eight Stoke 8
of adjacent characters shall be 3,175 mm + 0,254 mm
Nine Stoke 9
(0.125 in + 0.010 in) (see figure 16).
Symbol 1 Stoke 10
Symbol 2 Stoke 11
(Average edge is defined and discussed in clause 5.)
Stoke 12
Symbol 3
Symbol 4 Stoke 13
3.1 .I.2 The accumulation of spacing tolerances in any
common (fixed format) field is limited to the extent that
the accumulation does not infringe upon the boundaries
defining this field.
1) As used in this International Standard, the term “magnetic ink” means ink capable of being magnetized and sensed.
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IS0 1004:1995 (E) 0 IS0
3.1.2 Minimum space - any field side (see figure 19). (The typical edge of a printed char-
acter is not a straight line.)
The minimum space between the right average edge of
Average edge tolerance
adjacent characters, whether they are in the same field 5.3
or adjoining fields, can never be less than 2,921 mm
The average edge tolerance for all stroke edges shall
(0.115 in). This also applies to variable format fields.
be + 0,038 mm (+ 0.0015 in) applied to the dimensions
Maximum or other spacing requirements in variable
(measured from Q and @) that locate the edges. A typi-
fields shall be specified by the individual machine manu-
facturer involved.
cal illustration of this tolerance is shown in figure 20.
3.2 Alignment of characters
The average edge of the radii shall be tangential to the
average edge of the stroke and shall fall within the +
3.2.1 Definition
0,038 mm (+ 0.0015 in) tolerance specified for stroke
edges (See 2.2)
alignment: The relative vertical location of a character
with respect to adjacent characters within a given field.
5.4 Edge irregularity tolerance
The horizontal centre line of each character is indicated
on drawings of the printed character by the symbol El+
5.4.1 Peaks and valleys about the average edge are
These centre lines serve to establish vertical alignment permitted to extend to + 0,089 mm (+ 0.0035 in) from
the dimension locating the edge. An example is shown
of all characters, since all characters are designed
about the same horizontal centre line. in figure 21. However, when these occur the sum of the
edge present in the 0,038 mm to 0,089 mm (0.0015 in
3.2.2 Tolerances to 0.0035 in) zone shall not exceed 25% of the total
edge.
Vertical alignment tolerance is that which is consistent
with good printing practice and subject to the following 5.4.2 An occasional void can be present at the edge
and cause a valley that exceeds the limits mentioned
interpretations:
above. The maximum allowable size of such voids is
a) alignment of a line of characters printed in any specified in clause 6.
field should be such that the bottom edges of ad-
jacent characters within each field do not vary 5.4.3 An occasional excursion (such as feathering or
vertically by more than 0,381 mm (0.015 in) stringing out) can be present at the edge and extend be-
(see figure 17);
yond the 0,038 mm to 0,089 mm (0.0015 in to 0.0035
in) zone. Such occasional excursions are not consid-
b) on characters that do not come down to the ered to be edge irregularities, and are defined as extra-
“base” line (see figures 13, 14, and 16), the toler-
neous ink that is “attached” to the character. The
ance specified in a) applies to the horizontal cen- maximum allowable size and quantity of such excur-
tre line. sions is given in clause 8.
In measuring the size of such excursions, only the por-
4 Character skew
tion that extends beyond the 0,089 (0.0035 in) limit men-
tioned in 5.4.1 should be considered since the portion
The maximum allowable character skew is + 130
of the excursion in the 0,038 mm to 0,089 mm (0.0015
measured with respect to the bottom edge of the docu- in to 0.0035 in) zone is controlled by character edge ir-
ment. (See figure 18.)
regularity limits given in 5.4.1.
5.5 Minimum width of horizontal bars
5 Character tolerances
The distance between the average edges of any hori-
5.1 Dimensions zontal bar shall be at least 0,279 mm (0.011 in). (This
specification is an adjunct to the dimension specification
See figures 1 to 14 for dimensions of printed characters. locating each edge. This specification does not apply to
vertical bars since vertical bars are controlled entirely
5.2 Definition of “average edge” by the dimensions locating each edge.
average edge: An imaginary line that divides the irregu-
larities along the edge of a printed character so that the
summation of the white areas on one side of the line is
equal to the summation of the black areas on the other
2
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IS0 1004:1995 (E)
0 IS0
8 Extraneous ink
6 Voids
8.1 Definition
6.1 Definition
8.1 .I Extraneous ink, magnetic
specified outline
voids: The absence of ink within the
of the printed character.
Any magnetic ink which appears in the 15,9 mm (0.625
inch) MICR clear band other than the E 13 B MICR
6.2 Maximum allowable single void
characters. (See 8.2.1 .I and 8.2.2, and figure 24). The
MICR clear band is applicable to both the front and
6.2.1 The maximum allowable single void anywhere in
back of the document.
the character, including at an edge, shall be of a size
that can be contained entirely within the boundary of a
8.1.2 Extraneous ink, nonmagnetic
0,203 mm x 0,203 mm (0.008 in x 0.008 in) square,
with the following exception:
Any ink (nonmagnetic) appearing in the 8,0 mm (0.315
inch) optical clear band (area) that interferes with opti-
If the portion of the character involving a single
cal reading of E 13 B MICR characters. It is splatter,
void is two or more zones wide [each zone is
smear, tracking, feathering, stringing out, toning, back
0,330 mm (0.013 in) wide], then the maximum al-
offset, and so forth. (See 8.2.1.2, and figure 24). This
lowable single void must be completely sur-
clear area is defined in IS0 1831’ and includes the
rounded by ink and contained entirely within the
printing band for the MICR characters. The optical clear
boundary of a 0,254 mm x 0,254 mm (0.010 in x
band applies only to the document front.
0.008 in) square.
8.2 Limitations
In this case, voids at edges are not included and
are, therefore, limited to a 0,203 mm x 0,203 mm
8.2.1 Extraneous ink, front
(0.008 in x 0.008 in) square. (See figure 22.)
8.2.1 .I Magnetic ink
6.2.2 Single voids that are long and narrow are called
“needle” type voids. They are allowable in any length
Extraneous magnetic ink on the front of the document
anywhere on the character provided that they are no
within the MICR clear band is acceptable if the spots
wider than 0,051 mm (0.002 in), average edge to aver-
can be contained in a 0,08 mm x 0,08 mm (0.003 in x
age edge.
0.003 in) square.
6.3 Maximum allowable combined voids
Spots that cannot be contained in a 0,08 mm x 0,08
mm (0.003 in x 0.003 in) square are acceptable pro-
The combined areas of all voids, in any vertical column
vided that they can be contained in a 0,l mm x 0,l mm
or horizontal row nominally 0,330 mm (0.013 in) wide,
(0.004 in x 0.004 in) square and are limited to one per
shall not exceed 20% of the area of the column or row.
character space and total not more than five per field.
(See figure 23.)
Spots that are found to be located within the outermost
limits established by the character edge irregularity toler-
7 Uniformity of ink film
ance are to be considered under the character edge ir-
regularity specifications.
The ink deposited shall be uniformly distributed within
the outlines of each character. Conditions to be avoided
8.2.1.2 Non-magnetic ink
include excessive squeeze-out, halo, and other uneven
deposits.
Spots within the 8,0 mm (0.315 in) optical clear band
that can be contained inside a circle 0,2 mm (0.008 in)
A ridge of ink that outlines a character and that appears
in diameter are acceptable as long as no two spots are
dense in relation to the ink deposited within the charac-
closer than I,0 mm (0.040 in) to each other or to an E
ter is acceptable provided that it does not exceed 0,038
13 B character regardless of PCS values. See IS0
mm (0.0015 in) between its average edges. Such 1831 for the definitions of Visual Spectrum and Print
ridges are predominant in letterpress printing and some
Contrast Signal (PCS).
impact printing.
1) IS0 1831: 1980, Printing specifications for optical character recognition.
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IS0 1004:1995 (E)
0 IS0
8.2.2 Extraneous magnetic ink, back 10 Signal level
10.1 Definitions
Extraneous magnetic ink on the back of the document
within the area of the MICR clear and is not acceptable
10.1 .I
Signal level: The amplitude of the voltage
if the spots cannot be contained in a 0,15 mm x 0,15
waveform produced when a dc-magnetized printed char-
mm (0.006 in x 0.006 in) square.
acter is scanned by a suitable magnetic reading head.
A Typical character waveform of Stroke 12 (Symbol 3)
as it appears on the face of an oscilloscope is given in
9 Debossment (impression)
figure 25.
Penetration of the printed character into the surface of
10.1.2 Nominal signal level: The signal obtained
the paper is known as debossment. When it is exces-
from a properly printed reference printing sample, cali-
sive, it can be the cause of rejects or misreads. Signal
brated as 100 percent using the Wire Card Calibration
levels may be reduced or distorted because the mag-
procedure and suitable test equipment.
netic ink characters are displaced from the magnetic
pick-up device by the debossment depth. Debossment
The Wire Card Calibration procedure involves the meas-
on the face of the document may or may no cause frac-
tures of the paper fibers which are detectable on the re- urement of a standard magnetic flux generated by a
sinusoidal electrical current (I), flowing through a
verse side.
straight wire positioned parallel to the gap and within
the gap of a standard magnetic read head. Calibration
A category of equipment which can measure deboss-
ment to within a repeatability of 0,0025 mm (0.001 in) is is performed using procedures and test equipment as
described in 10.4.
the light section microscope. Typical vendors of this
equipment are Zeiss and Stangert.
The chart shown in figure 26 and the waveforms in fig-
ure 27 illustrate the nominal signal level for designated
This standard established 0,025 mm (0,001 in) as the
maximum allowable debossment. However, it is recog- peaks of each character when the Stroke 12 (Symbol 3)
is at 100 percent.
nized that this specification depth is frequently ex-
ceeded by letterpress printing, press numbering, and
10.1.3 Relative signal level: The ratio, stated as a
ribbon encoding without immediately causing MICR
percentage, that the signal level of a character being
reading problems. Additional tolerances beyond the
stated 0,025 mm (0.001 in) limit may be acceptable de- measured bears to the nominal signal level for that char-
acter with the reference Wire Card standard taken as
pending upon several associated factors such as signal
100 percent for the Stroke 12 (Symbol 3) (see figure
strength, uniformity of ink coverage, and evenness of
13).
debossment. Therefore, it is recommended before sam-
ple documents are rejected for exceeding these deboss-
ment specifications, that back-up evaluation and testing The signal level of the character being measured is ob-
tained using suitable procedures and test equipment.
for the above factors be employed.
(See 10.2.)
For example:
10.1.4 Secondary reference document: A paper
document specially printed in magnetic ink with a single
(1) Uneven debossment such as deeper penetra-
tion by a vertical narrow stroke of a character, Stroke 12 (Symbol 3) of the E 13 B font. This document
as compared to a broader portion of the same is of known relative signal level as determined by the
character coupled with insufficient signal from Wire Card Calibration procedure described in 10.4 for
the ink can cause rejects. use in calibration of equipment used to measure rela-
tive signal level. Secondary reference documents are
(2) Although uniform debossment of an entire char- selected such that the relative signal of the printing
acter with adequate signal strength probably will theron is as close as practical to 100 percent of the
not cause rejects, considering that these condi- nominal signal level. These documents are marked to in-
dicate their actual relative signal levels (See figure 28).
tions can occur, a further explanation of toler-
ances acceptable under the certain To perform as expected, MICR characters should be
circumstances is contained in annex A. printed to the nominal dimensions shown in figures 1
through 14.
4
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IS0 1004:1995 (E)
0 IS0
10.2.2.4
10.2 Test equipment and parameters The amplifier shall have the following charac-
teristics:
10.2.1 Test equipment
(1) Gain. The amplifier gain shall be such that an in-
10.2.1.1 A means for moving a document bearing the put sine wave of 10 mV + 0,2 mV peak-to-peak
dry magnetic ink printing from left to right (the charac- at 1 kHz, produces a sine wave output of 2,4 V
ters are scanned from right to left), in a direction paral- + 0,4 V peak-to-peak.
lel to a single gap magnetic read head, and including
means for holding the document in intimate contact with (2) Frequency response.
the face of a magnetic write head and read head.
(a) The amplifier gain shall not vary by more
than + 0,5 db from the 1 kHz gain over a
10.2.1.2 A dc-magnetizing head (write head) capable
frequency range of 200 Hz to 3 kHz.
of magnetizing the characters to saturation in a direc-
(b) The amplifier gain between the frequencies
tion parallel to the bottom reference edge and in the
plane of the printed characters. Note that saturation of 200 Hz and 75 Hz shall not drop more than
3 db below the 1 kHz gain.
the magnetic ink is important to achieve uniform signal
levels within any waveform and also readings which are
(c) The amplifier gain below 75 Hz shall not ex-
repeatable.
ceed the 1 kHz gain.
(d) The amplifier gain above 3 kHz shall drop
10.2.1.3 A single gap magnetic read head mounted
with the long axis of the gap perpendicular to the bot- on a smooth curve such that: at 5,l kHz +
600 Hz, the gain is 3 db below the 1 kHz
tom reference edge and parallel with the plane of the
gain; and at II,2 kHz + I,2 kHz, the gain is
printed characters. Considering the magnetic read head
12 db below the 1 kHz gain.
gap as a plane of negligible thickness, the plane of the
gap shall be perpendicular to the plane of the document
NOTE - A gain 3 db below a reference value is 0,707
and to the bottom reference edge of the document.
of the reference value; a gain 12 db below a reference
value is 0,25 of the reference value.
10.2.1.4 A linear amplifier to amplify the output of the
magnetic read head for presentation on an oscilloscope.
(3) Roll-Off. The high frequency roll-off charac-
teristics of the amplifier shall be equivalent to
10.2.1.5 An oscilloscope, or equivalent, for display of
that of a four section resistance-capacitance fil-
the voltage waveform(s) of the character(s) to be meas-
ured and the voltage waveform(s) of a calibrated Stroke ter with buffering between stages, that is, non-
peaking, and have an attenuation of 6 db per
12 (Symbol 3) on a secondary reference document.
octave per stage or 24 db per octave for the
10.2.2 Equipment parameters four stages.
10.2.2.1 The relative speed of the document to the (4) Linearity. At any frequency within the range
read head shall be 380 cm/s (150 in/s) within &- 2%. from 75 Hz to II,2 kHz + I,2 kHz, the amplifier
Combined character skew from all causes shall not ex- gain shall be linear within * 0,5 db for an input
voltage range of 3 mV to 25 mV peak-to-peak.
ceed I,5 degrees relative to the centre line of the read
head gap.
(5) Noise.
10.2.2.2 The magnetizing read head shall be such as
(a) With the input connection to ground, the
to produce dc magnetic saturation in printed characters
noise output shall not exceed the voltage
in the direction specified in 10.2.1.2. The leading pole
which is equivalent to one percent of the
relative to the printed character is to be the north pole.
nominal output signal level.
(b) A circuit diagram of a suitable amplifier is
10.2.2.3 The magnetic read head shall have a 0,076
mm (0.003 in) gap and a minimum resonant frequency given in annex A.
of 40 kHz. The height of the read head gap shall be
10.2.2.5 The oscilloscope may be of any commercially
6,35 mm (0.250 in). The head shall be shielded on all
sides, except the read face and the back, such that any available type intended for laboratory measurements
and equipped with a graticule bearing horizontal and
induced noise shall not cause a signal-to-noise ratio
vertical rulings.
less than 4O:l when reading 100 percent reference ma-
terial (Brush Clevite Read Head, part number BK1251,
or equivalent).
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0 IS0
IS0 1004:1995 (E)
10.3.3 An alternate procedure that is slightly more ac-
10.3 Testing procedure
curate but may take more time when measuring a large
number of documents may be used to determine rela-
The horizontal trace which appears on the face
10.3.1
tive signal strength as follows:
of the oscilloscope when the output of the amplifier is
connected to the ac input of the oscilloscope, but with
A secondary reference document with a cali-
no document being scanned, is adjusted to coincide
(1)
brated Stroke 12 (Symbol 3) character is placed
with the lowest ruling on the oscilloscope graticule.
in the transport and scanned. The average am-
plitude of the third and fifth peaks of this charac-
10.3.2 A secondary reference document with a Stroke
ter is then measured, using the highest
12 (Symbol 3) character is placed in the transport and
resolution possible on the oscilloscope.
scanned. Set the vertical gain to 2X magnification and
adjust the vertical centring so that the deflection from
the uppermost division to the baseline is 200 percent of This value is then scaled by dividing by the rela-
(2)
tive signal level of the secondary reference
the positive peak amplitude of the symbol being meas-
ured. This may be done as follows: Stroke 12 (Symbol 3) character and multiplying
by the nominal relative value for the character to
be measured (see figure 29). The resulting
Determine the number of major divisions on the
(1)
graticule in the vertical direction. value is the nominal signal level for the charac-
ter to be measured.
Divide this number by two.
0
To determine the relative signal level of any par-
(3)
Multiply this by the relative signal level percent- ticular character under test, measure the vertical
(3)
age of the secondary reference document. deflection of the appropriate positive peaks (fig-
Stroke 12 (Symbol 3) character being used and ure 29) and divide by the nominal signal level
for that character as determined above.
divide by the nominal value (see figure 29) for
the character to be measured. Adjust the verti-
cal gain so that the vertical deflection of the For example:
character being observed is equal to this calcu-
a If the relative signal level for the calibrated
( 1
lated deflection.
Stroke 12 (Symbol 3) character equals 104
percent and measures 800 mV on the oscil-
For example:
loscope, then the nominal voltage for a
a Eight major divisions are on the face of the Stroke 12 (Symbol 3) character is (800
( )
mV)*(100/104) = 769 mV. The nominal volt-
oscilloscope.
age for Stroke 13 (Symbol 4) cha
...
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