Analog signal modifying apparatus

Claim 2

Electric analog signal modifying apparatus comprising: an oscillator producing successive voltage rises and including direct current means responsive to a direct current analog signal to control the duration of the successive voltage rises of the oscillator dependent on the amplitude of the analog signal such that the interval between rises is inversely proportional to the analog signal amplitude during the interval, a constant amplitude pulse generator, and means coupling said oscillator and generator to cause the generator to produce said constant amplitude pulses at the intervals of said rises.

Claim 3

Apparatus according to claim 1 wherein said oscillator comprises a storage capacitor, and means responsive to said analog signal to charge and discharge said capacitor, whereby the charging rate and discharge time of said capacitor are dependent on said analog signal.

Claim 4

Apparatus according to claim 2 wherein said discharge means comprises switch means triggered by the charge voltage of said capacitor to discharge condition at a predetermined threshold voltage.

Claim 5

Apparatus according to claim 3 wherein said discharge means comprises a Schmitt trigger responsive to said capacitor charge voltage and said analog signal, and gate means on a path parallel with the capacitor and responsive to the Schmitt trigger to complete said path.

Claim 6

Apparatus according to claim 1 wherein said pulse generator comprises a storage capacitor, means to charge said capacitor, means responsive to the oscillator pulses to discharge said capacitor, and switch means triggered at a predetermined threshold voltage, and responsive to discharging of said capacitor lower than said voltage to produce a constant amplitude pulse during the interval of said lower voltage.

Claim 7

Apparatus according to claim 5 wherein said means to charge comprises a constant current source, whereby the interval of said lower voltage and of said pulse is substantially constant.

Claim 8

Apparatus according to claim 5 wherein said means to charge is a variable current source responsive to said analog signal to vary the interval of said lower voltage and of said pulse dependent on the amplitude of the analog signal during said interval.

Claim 9

Apparatus according to claim 1 characterized by current sensitive utilization means varying in impedance, and pulse output means interconnecting said pulse generator and utilization means, wherein said pulse output means comprises a current starved amplifier responsive to each pulse and to the instantaneous impedance of said utilization means to adjust the voltage amplitude of each pulse thereby to hold the pulse current constant with varying impedance.

Claim 10

Apparatus according to claim 8 wherein said utilization means comprises means for applying said pulses to an electrosensitive recording medium.

Claim 11

Apparatus according to claim 9 wherein said pulse applying means comprises electrodes on opposite sides of an electrolytic recording paper having a nonlinear gamma characteristic.

Claim 12

Apparatus according to claim 9 wherein the aforesaid pulse generator comprises means further responsive to said analog signal to vary the width of said pulses inversely dependent on the amplitude of the analog signal thereby to record on said paper with marks whose apparent density is substantially in linear relation to the analog signal.

Claim 13

Electrolytic facsimile apparatus for recording analog signals on electrolytic paper having a nonlinear gamma characteristic and a varying resistance to marking current comprising: an analog signal input terminal (A), a voltage controlled oscillaTor (VCO) including a first storage capacitor (C8), a current source (B+) for charging said first capacitor, a current starved amplifier (Q4) connected between said input terminal and capacitor for holding the charging rate of the capacitor linear, a gate (Q3) for discharging the first capacitor, and a first trigger circuit (ST1) for opening the gate, said first trigger circuit having a first voltage threshold (Et) at which it undergoes transition and being responsive to charge of said capacitor above said threshold to open said gate and discharge the first capacitor, thereby to produce a first sawtooth voltage (C) with a series of rises spaced by charging slopes at time intervals inversely proportional to the amplitude of the analog signal; a differentiator network (N3) converting said rises into a series of voltage spikes (D); a pulse generator (PG) including a second storage capacitor (C12), a variable current source (Iv) for charging said second capacitor and comprising voltage amplifying means (Q15, Q7) coupled to said input terminal and responsive to said analog signal to vary the current supplied to, and the charging rate of, said second capacitor, a discharge amplifier (Q8) connected between said differentiator network and said second capacitor and responsive to said voltage spikes to form a discharge path for said second capacitor, charge and discharge of said capacitor producing a second sawtooth voltage (E'') with spaced rises having slopes varying in inverse proportion to the amplitude of the analog signal, whereby said slopes are below a second threshold voltage (E9) for varying periods, and a second trigger circuit (ST2) connected to said second capacitor and responsive to said second sawtooth voltage to produce a second series of constant amplitude voltage pulses (E'') individually varying in duration as the periods sawtooth voltage below said threshold, pulse output means including a second power supply (HV) and a current starved amplifier (Q16) connected between second trigger circuit and said power supply, an electrolytic recorder including opposed electrodes connected through said power supply to said second current starved amplifier for applying a marking current to an electrolytic paper therebetween during the pulses of said second series, said second series of voltage pulses (F'') having, as a result of the varying duration of the pulse periods, a voltage versus density characteristic compensating for the nonlinear gamma characteristic of the paper, and said second current starved amplifier being responsive to variations in the resistance of said paper to said marking current to adjust the marking current to compensate for said resistance variations.

Claim 14

Electrolytic facsimile apparatus for recording analog signals on electrolytic paper having a nonlinear gamma characteristic and a varying resistance to marking current comprising: an analog signal input terminal (A), a voltage controlled oscillaTor (VCO) including a first storage capacitor (C8), a current source (B+) for charging said first capacitor, a current starved amplifier (Q4) connected between said input terminal and capacitor for holding the charging rate of the capacitor linear, a gate (Q3) for discharging the first capacitor, and a first trigger circuit (ST1) for opening the gate, said first trigger circuit having a first voltage threshold (Et) at which it undergoes transition and being responsive to charge of said capacitor above said threshold to open said gate and discharge the first capacitor, thereby to produce a first sawtooth voltage (C) with a series of rises spaced by charging slopes at time intervals inversely proportional to the amplitude of the analog signal; a differentiator network (N3) converting said rises into a series of voltage spikes (D); a pulse generator (PG) including a second storage capacitor (C12), a variable current source (Iv) for charging said second capacitor and comprising voltage amplifying means (Q15, Q7) coupled to said input terminal and responsive to said analog signal to vary the current supplied to, and the charging rate of, said second capacitor, a discharge amplifier (Q8) connected between said differentiator network and said second capacitor and responsive to said voltage spikes to form a discharge path for said second capacitor, charge and discharge of said capacitor producing a second sawtooth voltage (E'') with spaced rises having slopes varying in inverse proportion to the amplitude of the analog signal, whereby said slopes are below a second threshold voltage (E9) for varying periods, and a second trigger circuit (ST2) connected to said second capacitor and responsive to said second sawtooth voltage to produce a second series of constant amplitude voltage pulses (E'') individually varying in duration as the periods sawtooth voltage below said threshold, pulse output means including a second power supply (HV) and a current starved amplifier (Q16) connected between second trigger circuit and said power supply, an electrolytic recorder including opposed electrodes connected through said power supply to said second current starved amplifier for applying a marking current to an electrolytic paper therebetween during the pulses of said second series, said second series of voltage pulses (F'') having, as a result of the varying duration of the pulse periods, a voltage versus density characteristic compensating for the nonlinear gamma characteristic of the paper, and said second current starved amplifier being responsive to variations in the resistance of said paper to said marking current to adjust the marking current to compensate for said resistance variations.