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MICR Automatic Gain Control

IP.com Disclosure Number: IPCOM000093282D
Original Publication Date: 1967-Aug-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 2 page(s) / 35K

Publishing Venue

IBM

Related People

Arnold, RW: AUTHOR

Abstract

The arrangement provides automatic gain control especially useful with single gap Magnetic Ink Character Recognition systems. Signals from read head 3 are supplied to preamplifier 5 which can have a gain of 100. for example. The output of preamp 5 is supplied through filter 7 to analog clamp 9, filter 7 eliminating certain noise signals arising in head 3. Clamp 9 eliminates any signals due to noise between the characters. The output of clamp 9 is supplied to one input of operational amplifier 11 which is provided with the usual feedback loop including resistor R1. In the inputs to amplifier 11, a pair of controlled impedance devices 13 and 15 are provided which can be, for example, field effect transistors.

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MICR Automatic Gain Control

The arrangement provides automatic gain control especially useful with single gap Magnetic Ink Character Recognition systems. Signals from read head 3 are supplied to preamplifier 5 which can have a gain of 100. for example. The output of preamp 5 is supplied through filter 7 to analog clamp 9, filter 7 eliminating certain noise signals arising in head 3. Clamp 9 eliminates any signals due to noise between the characters. The output of clamp 9 is supplied to one input of operational amplifier 11 which is provided with the usual feedback loop including resistor R1. In the inputs to amplifier 11, a pair of controlled impedance devices 13 and 15 are provided which can be, for example, field effect transistors.

Devices 13 and 15 are characterized by having a controllable impedance which can be governed by suitable signals supplied to them. The output of amplifier 11 is supplied to output operational amplifier 17. The output of amplifier 17 is supplied to terminal E0.

The output of amplifier 11 is also supplied to the input of a track-hold circuit
19. The latter is constructed and arranged so that normally the output of circuit 19 follows the variations in the input signal. but upon the supply to it of a suitable control signal, the circuit output is maintained at the value which it has at the time the control signal is first supplied. In the present case, the control signal is supplied to a terminal PD from a peak detector circuit, not shown, which indicates the fact that the peak value of the first portion of a character being read by the system has been reached. The output of circuit 19 is supplied to the input of a 100 millivolt threshold circuit 21. The latter is utilized...