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Variable Velocity Reader Logic

IP.com Disclosure Number: IPCOM000076136D
Original Publication Date: 1972-Jan-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 39K

Publishing Venue

IBM

Related People

Houdek, ME: AUTHOR

Abstract

An optical reader which employs a hand-held single-position reading device such as a pencil unit involves variation in velocity of the device. This velocity variation is controlled by measuring each digit read time and comparing it with the previous digit read time to obtain a reference. A 2-of-6 bar code, as shown in Figs. 2 and 3, is used in reading a set of marks spaced to indicate "1"s or "0"s. A short distance between marks is a logical 0 and a long distance is a logical 1. The first space is always a zero, making a reference time to compare the length of the second space between marks. The second through fifth space represent a BCD code (except for the 7-digit). The last space of the code is such to make the total number of one bits equal to two; thus each character has two 1-bits and four 0-bits -- a 2-of-6 code.

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Variable Velocity Reader Logic

An optical reader which employs a hand-held single-position reading device such as a pencil unit involves variation in velocity of the device. This velocity variation is controlled by measuring each digit read time and comparing it with the previous digit read time to obtain a reference. A 2-of-6 bar code, as shown in Figs. 2 and 3, is used in reading a set of marks spaced to indicate "1"s or "0"s. A short distance between marks is a logical 0 and a long distance is a logical 1. The first space is always a zero, making a reference time to compare the length of the second space between marks. The second through fifth space represent a BCD code (except for the 7-digit). The last space of the code is such to make the total number of one bits equal to two; thus each character has two 1-bits and four 0-bits -- a 2-of-6 code.

As shown in Fig. 1, the code reading is carried out using the following method: As the first mark is sensed by the read head, the X-counter is allowed to start counting pulses from an oscillator. As the second mark is read, the count in the X-counter represents the time (distance) between the first two marks of the encoded character.

Since the first bit of the code is always a 0-bit 2X is transferred into the Y Register. The multiplication of X is accomplished by transferring X0 to Y1, X1 to Y2, etc. (the order of the bits in the X and Y registers are X5X4X3X2X1X0 and Y5Y4Y3Y2Y1Y0, respectively). The value in the Y r...