Browse Prior Art Database

Multilevel F2F Code

IP.com Disclosure Number: IPCOM000045449D
Original Publication Date: 1983-Mar-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 2 page(s) / 48K

Publishing Venue

IBM

Related People

Shay, RJ: AUTHOR

Abstract

The density of a self-clocking magnetic stripe is increased through the use of superimposed binary codes, recorded at selected field strengths. The codes can be simultaneously or separately detected. A record 10, such as a credit card, is provided with a magnetic stripe 11 for sensing by a read head 12. Fig. 2 illustrates a code pattern on stripe 11 wherein the sign (+ or -) indicates the polarity of recording and the numerical value (1 or 2) indicates the relative strength of the recorded flux field. Fig. 3 shows a pattern of pulses produced by a magnetic transducer passing the stripe 11. These pulses vary in magnitude as a function of the polarity and strength of adjacent recorded areas. That is, adjacent opposite polarity regions recorded at 500 gauss give greater output than such regions recorded at 300 gauss.

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Multilevel F2F Code

The density of a self-clocking magnetic stripe is increased through the use of superimposed binary codes, recorded at selected field strengths. The codes can be simultaneously or separately detected. A record 10, such as a credit card, is provided with a magnetic stripe 11 for sensing by a read head 12. Fig. 2 illustrates a code pattern on stripe 11 wherein the sign (+ or -) indicates the polarity of recording and the numerical value (1 or 2) indicates the relative strength of the recorded flux field. Fig. 3 shows a pattern of pulses produced by a magnetic transducer passing the stripe 11. These pulses vary in magnitude as a function of the polarity and strength of adjacent recorded areas. That is, adjacent opposite polarity regions recorded at 500 gauss give greater output than such regions recorded at 300 gauss. In accordance with the known F2F code format, there is a regular pattern of flux transitions, labeled C. Ones or zeroes are recorded by the presence or absence of transitions located approximately halfway between the transitions C. In my code, each is capable of recording two independent data bits, A and B. These bits are defined as follows: a 2 to -2 transition between adjacent clock signals represents A=1, B=1. The absence of any transition between adjacent clock signals means A=0, B=0. A less than full transition, with a polarity change, produces A=0, B=1. A less than full transition, without a polarity change, means that A=1, B=0...