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Browse Prior Art Database

Card Reader Timing Pulse Generator

IP.com Disclosure Number: IPCOM000095752D
Original Publication Date: 1964-Jun-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 57K

Publishing Venue

IBM

Related People

Patterson, JL: AUTHOR

Abstract

A timing pulse generator for a punched or a marked card reader permits random feed. The feedrolls of the card reader are arranged to drive a slotted timing disk SD to sweep a light beam over a comparator Comparator C can be a lumped element device, as shown, or an integrated semiconductor device. It comprises a plurality of pairs of diodes P1-D1... P10-D10, arranged back-to-back along a voltage dividing network DN with one terminal DT of all of the diode pairs in common. One diode P1...P10 of each of the diode pairs is essentially a photodiode which conducts in response to impinging light. The switching diode D1...D10 of each pair conducts only when forwardly biased. The circuit values are such that conduction of a diode does not upset the established voltage levels.

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Card Reader Timing Pulse Generator

A timing pulse generator for a punched or a marked card reader permits random feed. The feedrolls of the card reader are arranged to drive a slotted timing disk SD to sweep a light beam over a comparator Comparator C can be a lumped element device, as shown, or an integrated semiconductor device. It comprises a plurality of pairs of diodes P1-D1... P10-D10, arranged back-to- back along a voltage dividing network DN with one terminal DT of all of the diode pairs in common. One diode P1...P10 of each of the diode pairs is essentially a photodiode which conducts in response to impinging light. The switching diode D1...D10 of each pair conducts only when forwardly biased. The circuit values are such that conduction of a diode does not upset the established voltage levels.

With the switches S1, S2 and S3 set to the left-hand contact, as shown, all of the switching diodes, save the last diode D10, are back-biased by the supply voltage V. Thus, a change in current flow is produced as the light beam hits the photodiode P10. The pulse of current consequently flowing through the primary winding of transformer T provides a large voltage pulse across a highly inductive secondary. This voltage pulse is amplified and applied through switch S3 as a reset pulse to ramp generator RG resetting this to zero in readiness for the next scan.

When a card passes a photocard lever PCL, the change of light intercepted is arranged to throw electronic switches S1, S2 and S3 at column zero time to the right-hand contact in each case. Since the cards approach the feedrolls at random times, the operational amplifier will have accumulated a voltage v usually less than the supply voltage V at the output terminal. This output...