Signalling circuit for indicating the presence of information

Claim 2

The combination comprising: a system input terminal adapted to receive black video information signals and blacker-than-black signals from a scanning system; bistable means, having a first bistable-means input terminal and a second bistable-means input terminal and having a system output terminal, for providing a signal to said system output terminal between the time that a signal is received on said first bistable-means input terminal and the time that a signal is received on said second bistable-means input terminal; said first bistable-means input terminal being electrically connected to said system input terminal; control means, electrically connected To said second bistablemeans input terminal, for applying a voltage to said second bistable-means input terminal whenever no black video information signal is received between consecutive blackerthan-black signals, whereby said system output terminal provides a signal indicating the time at which a video information signal appears at said system input terminal and the time that a full sweep is made by said scanning system with no video information signal appearing; said control means comprising an AND gate having its output terminal electrically connected to said second bistable-means input terminal and having a first AND gate input terminal and a second AND gate input terminal; first pulse generating means having an output electrically connected to said first AND gate input terminal for generating a voltage pulse between the termination of each of the unblanking signals of said scanning system and the start of video information on said system input terminal; and second pulse generating means, having its output electrically connected to said second AND gate input terminal for generating a voltage pulse in synchronism with said unblanking pulse of said scanning system, whereby said AND gate provides a voltage pulse to said second bistable means input terminal after any sweep of said scanning system in which there is no video information signal.

Claim 3

Apparatus for generating a start-of-character signal and an end-of-character signal for a character recognition device having a scanner comprising: a first input terminal adapted to receive video signals and to receive retrace scanner signal; a second input terminal adapted to receive scanner unblanking signals; a signal output terminal adapted to provide said start-of-character signal and said end-of-character signal; a first and second noncomplementing flip-flop; a differentiator; an inverter; said first input terminal being electrically connected to the rest input of said first flip-flop and to the second input of said second flip-flop; said second input terminal being electrically connected to the input of said differentiator and to the input of said inverter; said signal output terminal being electrically connected to the output terminal of said second flip-flop; the output of said differentiator being electrically connected to the set terminal of said first flip-flop; and a logical AND gate having an output terminal electrically connected to the first input of said second flip-flop and having two input terminals, one electrically connected to the output of said first flip-flop and the other being electrically connected to the output of said inverter.

Claim 4

Apparatus for generating a start-of-character signal and an end-of-character signal for a character recognition device having a scanner comprising: a first input terminal adapted to receive video signals and to receive retrace scanner signal; a second input terminal adapted to receive scanner unblanking signals; a signal output terminal adapted to provide said start-of-character signal and said end-of-character signal; a first and second noncomplementing flip-flop; a differentiator; an inverter; said first input terminal being electrically connected to the rest input of said first flip-flop and to the second input of said second flip-flop; said second input terminal being electrically connected to the input of said differentiator and to the input of said inverter; said signal output terminal being electrically connected to the output terminal of said second flip-flop; the output of said differentiator being electrically connected to the set terminal of said first flip-flop; and a logical AND gate having an output terminal electrically connected to the first input of said second flip-flop and having two input terminals, one electrically connected to the output of said first flip-flop and the other being electrically connected to the output of said inverter.

Claim 5

Apparatus for providing a start-of-character signal and an end-of-character signal for a character recognition device having a scanner, comprising: an input terminal to receive video signals and blanking signal from said scanner; a second input terminal adapted to receive unblanking voltages from said scanner; an output terminal adapted to provide start-of-character signals and said end-of-charater signals to a utility device; said first and second noncomplementing flip-flops; said first input terminal electrically connected to the reset input terminal of said first flip-flop and to the set input terminal of said second flip-flop; said output terminal electrically connected to the output of said second flip-flop; a differentiator; an inverter; said second input terminal being electrically connected to the input of said differentiator and to the input of said inverter; the output terminal of said differentiator being electrically connected to the set terminal of said first flip-flop; a delay line having its input electrically connected to the output of said first flip-flop; a logical AND gate having one input electrically connected to the output of said delay line, and having a second input electrically connected to the output of saiD inverter, and having its output electrically connected to the reset terminal of said second flip-flop; and a differentiator having its input electrically connected to the output of said second flip-flop and having its output electrically connected to said output terminal.

Claim 6

Apparatus for providing a start-of-character signal and an end-of-character signal for a character recognition device having a scanner, comprising: an input terminal to receive video signals and blanking signal from said scanner; a second input terminal adapted to receive unblanking voltages from said scanner; an output terminal adapted to provide start-of-character signals and said end-of-charater signals to a utility device; said first and second noncomplementing flip-flops; said first input terminal electrically connected to the reset input terminal of said first flip-flop and to the set input terminal of said second flip-flop; said output terminal electrically connected to the output of said second flip-flop; a differentiator; an inverter; said second input terminal being electrically connected to the input of said differentiator and to the input of said inverter; the output terminal of said differentiator being electrically connected to the set terminal of said first flip-flop; a delay line having its input electrically connected to the output of said first flip-flop; a logical AND gate having one input electrically connected to the output of said delay line, and having a second input electrically connected to the output of saiD inverter, and having its output electrically connected to the reset terminal of said second flip-flop; and a differentiator having its input electrically connected to the output of said second flip-flop and having its output electrically connected to said output terminal.

Claim 7

A signalling circuit for providing end-of-character signals for a scanner, comprising: a video pulse input terminal adapted to receive video information from said scanner; a first flip-flop; said first flip-flop being characterized by having two vacuum tube triodes with the grid of each electrically connected to the plate of the other through a capacitive crossover network and being biased to operate in the bistable mode; said video pulse input terminal being electrically coupled to the grid of a first of said vacuum tube triodes of said first flip-flop; a trace pulse input terminal adapted to receive differentiated unblanking signal; first pulse amplifier means; said trace pulse input terminal electrically connected to the input of said first pulse amplifying means; the output of said first pulse amplifying means being electrically connected to the grid of the second of said vacuum tubes in said first flip-flop; a first cathode follower; the plate of said second of said vacuum tubes in said first flip-flop being electrically connected to the input of said first cathode follower; a first diode having its cathode electrically connected to the output of said first cathode follower; a retrace pulse input terminal adapted to receive inverted differentiated trailing edges of unblanking pulses; a second diode having its cathode electrically connected to said retrace input terminal; unblanking a first resistor being electrically connected at one end to the anodes of said first and second diodes and being adapted to be connected to a source of positive voltage at its other end; a second pulse amplifying means having its input electrically connected to the anodes of said first and second diodes; a second flip-flop; said second flip-flop being characterized by having a third and fourth vacuum tube having their plates and grids electrically coupled through crossover circuits and being biased so as to operate in the bistable mode; said video pulse input terminal being electrically connected to the input of said third vacuum tube of said second flip-flop; the output of said second pulse amplifier being electrically connected to the grid of said fourth vacuum tube through its crossover network; a resistor-capacitor differentiator having its input electrically connected to the plate of said third vacuum tube; an output terminal adapted to provide end-of-character signals; and a second cathode follower having its input electrically connected to said differentiator and having its output electrically connected to said output terminal.

Claim 8

A signalling circuit for providing end-of-character signals for a scanner, comprising: a video pulse input terminal adapted to receive video information from said scanner; a first flip-flop; said first flip-flop being characterized by having two vacuum tube triodes with the grid of each electrically connected to the plate of the other through a capacitive crossover network and being biased to operate in the bistable mode; said video pulse input terminal being electrically coupled to the grid of a first of said vacuum tube triodes of said first flip-flop; a trace pulse input terminal adapted to receive differentiated unblanking signal; first pulse amplifier means; said trace pulse input terminal electrically connected to the input of said first pulse amplifying means; the output of said first pulse amplifying means being electrically connected to the grid of the second of said vacuum tubes in said first flip-flop; a first cathode follower; the plate of said second of said vacuum tubes in said first flip-flop being electrically connected to the input of said first cathode follower; a first diode having its cathode electrically connected to the output of said first cathode follower; a retrace pulse input terminal adapted to receive inverted differentiated trailing edges of unblanking pulses; a second diode having its cathode electrically connected to said retrace input terminal; unblanking a first resistor being electrically connected at one end to the anodes of said first and second diodes and being adapted to be connected to a source of positive voltage at its other end; a second pulse amplifying means having its input electrically connected to the anodes of said first and second diodes; a second flip-flop; said second flip-flop being characterized by having a third and fourth vacuum tube having their plates and grids electrically coupled through crossover circuits and being biased so as to operate in the bistable mode; said video pulse input terminal being electrically connected to the input of said third vacuum tube of said second flip-flop; the output of said second pulse amplifier being electrically connected to the grid of said fourth vacuum tube through its crossover network; a resistor-capacitor differentiator having its input electrically connected to the plate of said third vacuum tube; an output terminal adapted to provide end-of-character signals; and a second cathode follower having its input electrically connected to said differentiator and having its output electrically connected to said output terminal.