Browse Prior Art Database

Automatic Threshold Control Circuit

IP.com Disclosure Number: IPCOM000097413D
Original Publication Date: 1962-Nov-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 53K

Publishing Venue

IBM

Related People

Villante, AE: AUTHOR

Abstract

The circuit automatically adjusts the threshold level of quantizers in a character recognition system to enable the system to read high signal documents more reliably. Multitrack sensing devices 10 supply signals in parallel channels corresponding to the sensed characters to rectifiers and amplifiers 11 and then to quantizers 12. The signals from 10 are also applied to threshold control circuit 13.

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Automatic Threshold Control Circuit

The circuit automatically adjusts the threshold level of quantizers in a character recognition system to enable the system to read high signal documents more reliably. Multitrack sensing devices 10 supply signals in parallel channels corresponding to the sensed characters to rectifiers and amplifiers 11 and then to quantizers 12. The signals from 10 are also applied to threshold control circuit
13.

Circuit 13 has a plurality of parallel connected transistor input stages 14...
18. Each stage is associated with and receives signals at its base over conductor 19 from one of the channels of signals supplied by 10. The collectors of stages 14... 18 connect to common conductor 20. These stages, in the absence of input signals, are biased a predetermined level below cutoff by networks comprising resistors 21 and 22 and resistors 23. When a signal which exceeds the predetermined bias level is present in any channel, the transistor in the associated stage conducts and a corresponding signal appears on conductor
20. Since the stages 14... 18 are connected in parallel, the signal on 20 is proportional to the largest of the signals supplied from 10.

A signal on conductor 20 is coupled to the base of and renders conductive transistor emitter follower stage 24 so that capacitor 25 is quickly charged. The voltage on 25 at this time corresponds to the signal on conductor 20 and controls transistor output stage 26. The signal on conductor 27 ad...