Browse Prior Art Database

Data Recovery Circuit

IP.com Disclosure Number: IPCOM000089108D
Original Publication Date: 1977-Sep-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 2 page(s) / 49K

Publishing Venue

IBM

Related People

Maillet, JC: AUTHOR

Abstract

The drawing shows a data recovery circuit to be used in a magnetic badge reader, wherein the data to be read are recorded on a magnetic recording media which is manually moved past a transducing head.

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Data Recovery Circuit

The drawing shows a data recovery circuit to be used in a magnetic badge reader, wherein the data to be read are recorded on a magnetic recording media which is manually moved past a transducing head.

Since the magnetic recording media is manually moved, large variations of speed and acceleration have to be taken into account during the reading operation, the electrical signal from the transducing head being proportional to the badge speed.

The track magnetization corresponding to a binary sequence is represented by (a), the transducing head generating a read head signal therefrom. This signal is amplified by amplifier 1 having differential inputs to cancel out miscellaneous induced common-mode noise. A low-pass filter, comprising capacitor C and resistor R, rejects high frequency pick-up signals. The amplified read signal is represented in (b).

The output of amplifier 1 is applied to the input of a Schmitt trigger 2 through capacitor C1 and resistor R1. The time constant of capacitor C1 and resistor R1 is chosen greater than the maximum bit time in order to transmit a lower speed head signal without distortion.

The amplified head signal drives a voltage peak detector 3 which controls the triggering levels of Schmitt trigger 2 through variable threshold circuit 4. The amount of positive feedback applied to the Schmitt trigger through circuit & is equal to a fixed value plus a value proportional to the peak voltage. As the input signal increa...