Browse Prior Art Database

Clock Recovery in a Magnetic Badge Reader

IP.com Disclosure Number: IPCOM000087106D
Original Publication Date: 1976-Dec-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 2 page(s) / 39K

Publishing Venue

IBM

Related People

Debord, P: AUTHOR [+3]

Abstract

A specially designed magnetic head allows automatic clock recovery in a magnetic badge reader regardless of the reading speed.

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Clock Recovery in a Magnetic Badge Reader

A specially designed magnetic head allows automatic clock recovery in a magnetic badge reader regardless of the reading speed.

Clock recovery is achieved using a magnetic head, shown in Fig. 1, provided with two gaps separated by a distance W = [n + (1/2)] (1/N) inch. where n is an integer with as small a value as possible and N is the bit density (number of bits recorded per inch).

As shown in Fig. 2, data are encoded using a bifrequency code. After shaping, the signal output looks like a train of pulses, with the distance between some consecutive pulses being roughly twice that between the other pulses. As the second gap is delayed by an odd-number of times the half-bit length, the clock is directly provided by ORing the shaped outputs of the two gaps.

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