Apparatus for interpreting Code 39 bar code data

In a system for optically reading Code 39 bar code data wherein said system comprises (i) an optical code pen for reading bar code data and for producing an analog electrical output signal indicative of such data, and (ii) electrical conditioning means connected to said pen to receive said output and to produce a digital output signal indicative of said bar code data, said digital signal being characterized by relatively narrow and/or wide bars separated by relatively narrow and/or wide spaces, apparatus for interpreting said digital output signal of said system, said apparatus comprising:

• (a) means connected to receive said digital output signal and for measuring the time duration of each space between bars, said time duration data for all spaces in a code character being stored,
• (b) means for receiving said code character time duration data and for identifying the minimum and maximum width spaces,
• (c) means for producing a first space cutoff value of a time duration approximately 1.5 times the time duration of the minimum width space,
• (d) means for producing a second space cutoff value of a time duration approximately equal to one-half of the sum of the time durations of the minimum and maximum space widths,
• (e) means for comparing said first and second space cutoff values and for using the greater of such values as a reference against which all of the spaces in said characters are measured, those spaces having a time duration greater than that of said reference space cutoff value then being interpreted as wide spaces and those spaces having a time duration less than that of said reference space cutoff value then being interpreted as narrow spaces.

In a system for optically reading Code 39 bar code data wherein said system comprises (i) an optical code pen for reading bar code data and for producing an analog electrical output signal indicative of such data, and (ii) electrical conditioning means connected to said pen to receive said output and to produce a digital output signal indicative of said bar code data, said digital signal being characterized by relatively narrow and/or wide bars separated by relatively narrow and/or wide spares, apparatus for interpreting said digital output signal of said system, said apparatus comprising:

• (a) means connected to receive said digital output signal and for measuring the time duration of each bar and of each space between bars, said time duration data for all bars and all spaces in a code character being stored,
• (b) means for receiving said code character time duration data and for identifying the minimun and maximum width bars,
• (c) means for producing a first bar cutoff value of a time duration approximately 1.5 times the time duration of the minimum width bar,
• (d) means for producing a second bar cutoff value of a time duration approximately equal to one-half of the sum of the time durations of the minimum and maximum bar widths,
• (e) means for comparing said first and second bar cutoff values and for using the greater of such values as a reference against which all of the bars in said characters are measured, those bars having a time duration greater than that of said reference bar cutoff value then being interpreted as wide bars and those bars having a time duration less than that of said reference bar cutoff value then being interpreted as narrow bars,
• (f) means for receiving said code character time duration data and for identifying the minimum and maximum width spaces,
• (g) means for producing a first space cutoff valve of a time duration approximately 1.5 times the time duration of the minimum width space,
• (h) means for producing a second space cutoff value of a time duration approximately equal to one-half of the sum of the time durations of the minimum and maximum space widths, and
• (i) means for comparing said first and second space cutoff values and for using the greater of such values as a reference against which all of the spaces in said characters are measured, those spaces having a time duration greater than that of said reference space cutoff value then being interpreted as wide spaces and those spaces having a time duration less than that of said reference space cutoff value then being interpreted as narrow spaces.