Secret telephony

Claim 2

In secret telephony, means to analyze speech message waves into slowly varying currents representative of energy variations in respective portions of the speech frequency band, distributor means for rapidly switching fragments of said currents to line in rotation, a source of masking currents for each of said slowly varying currents, the masking currents each varying in magnitude in random manner, and sychronously operating means for adding masking current from a respective source to each fragment of the switched currents.

Claim 3

In a speech privacy system, means for deriving from each of a plurality of different frequency regions of the speech band a slowly varying speech-defining signal, a transmission channel, means for rapidly switching fragments of said signals to said transmission channel in rotation, means for supplying masking currents varying in amplitude in random manner and means for adding portions of such masking currents to said switched fragments.

Claim 4

In a speech privacy system, means for deriving from each of a plurality of different frequency regions of the speech band a slowly varying speech-defining signal, a transmission channel, means for rapidly switching fragments of said signals to said transmission channel in rotation, means for supplying masking currents varying in amplitude in random manner and means for adding portions of such masking currents to said switched fragments.

Claim 5

In a speech privacy system, means for deriving from each of a plurality of different frequency regions of the speech band a slowly varying speech-defining signal, a transmission channel, cyclically operating switching mechanism for sampling said signals in rapid rotation and switching the sampled portions to said transmission channel, whereby a current is produced in said channel which is a composite of the various signals juxtaposed in time, means to add extraneous currents to said current in said channel to mask its identity for purposes of privacy, and means for reducing the total amplitude range of the resultant currents transmitted.

Claim 6

In a speech privacy system, means for deriving from each of a plurality of different frequency regions of the speech band a slowly varying speech-defining signal, a transmission channel, cyclically operating switching mechanism for sampling said signals in rapid rotation and switching the sampled portions to said transmission channel, whereby a current is produced in said channel which is a composite of the various signals juxtaposed in time, means to add extraneous currents to said current in said channel to mask its identity for purposes of privacy, and means for reducing the total amplitude range of the resultant currents transmitted.

Claim 7

In a speech privacy system, means for deriving from each of a plurality of different frequency regions of the speech band a slowly varying speech-defining signal, a transmission channel, distributor means for selecting short portions of said signals in rapid succession and impressing them upon said channel for transmission, a record of random current strengths, means to reproduce the recorded currents and add them to the signals in said channel whereby the amplitude relations of the signals are altered, and means to limit the total amplitude of the transmitted currents comprising means to reduce by a fixed amount the amplitudes in excess of a predetermined maximum.

Claim 8

In a speech privacy system, means for deriving from each of a plurality of different frequency regions of the speech band a slowly varying speech-defining signal, a transmission channel, distributor means for selecting short portions of said signals in rapid succession and impressing them upon said channel for transmission, a record of random current strengths, means to reproduce the recorded currents and add them to the signals in said channel whereby the amplitude relations of the signals are altered, and means to limit the total amplitude of the transmitted currents comprising means to reduce by a fixed amount the amplitudes in excess of a predetermined maximum.

Claim 9

In a speech privacy system, means for deriving from each of a plurality of different frequency regions of the speech band a slowly varying speech-defining signal, a transmission channel, electronic commutator means of the type having a movable beam sweeping in succession over a plurality of electrodes, means to place said signals in circuit with electrodes of said commutator whereby fragments of said signals are impressed on said transmission channel in rapid succession, a record having recorded thereon a random successon of currents of various amplitudes, and means to pick off said recorded currents and apply them to electrodes of said electronic commutator means, said commutator means operating to add the currents from said record to the fragments of signals impressed on said channel to mask the identity of the latter.

Claim 10

In a speech privacy system, means for deriving from each of a plurality of different frequency regions of the speech band a slowly varying speech-defining signal, a transmission channel, electronic commutator means of the type having a movable beam sweeping in succession over a plurality of electrodes, means to place said signals in circuit with electrodes of said commutator whereby fragments of said signals are impressed on said transmission channel in rapid succession, a record having recorded thereon a random successon of currents of various amplitudes, and means to pick off said recorded currents and apply them to electrodes of said electronic commutator means, said commutator means operating to add the currents from said record to the fragments of signals impressed on said channel to mask the identity of the latter.

Claim 11

In a speech transmission system, means at a transmitting point for deriving from each of a plurality of different frequency regions of the speech message band a slowly varying current representative of the energy variations with time occurring in the respective frequency region of the speech message band, a transmission channel leading to a receiving point, rapidly operating distributor means for transmitting to said channel short fragments of said currents in rotation, synchronously operating distributor means at the receiving point for reproducing from said transmitted currents a plurality of slowly varying currents corresponding respectively to the slowly varying currents derived at the transmitter, means at the transmitting point from adding an individual masking current to each such transmitted fragment of current, means at the receiving point for subtracting a duplicate of each such individual masking current from the received currents, and means for reconstructing the speech message under control of the reproduced slowly varying currents.

Claim 12

In a speech transmission system, means at a transmitting point for deriving from each of a plurality of different frequency regions of the speech message band a slowly varying current representative of the energy variations with time occurring in the respective frequency region of the speech message band, a transmission channel leading to a receiving point, rapidly operating distributor means for transmitting to said channel short fragments of said currents in rotation, synchronously operating distributor means at the receiving point for reproducing from said transmitted currents a plurality of slowly varying currents corresponding respectively to the slowly varying currents derived at the transmitter, means at the transmitting point from adding an individual masking current to each such transmitted fragment of current, means at the receiving point for subtracting a duplicate of each such individual masking current from the received currents, and means for reconstructing the speech message under control of the reproduced slowly varying currents.

Claim 13

In a speech transmission system, means to analyze speech message currents into a plurality of slowly varying currents simultaneously existent in a corresponding plurality of separate circuits, distributor means to switch short fragments of said currents to line in rapid rotation, means to separately produce a corresponding plurality of currents each varying in amplitude in time correspondence with the switching rate of said distributor means, and each having random distribution of amplitude among successive switching times, and means to add said separately produced currents individually to the fragments of said slowly varying currents as the latter are switched to line, to mask the identity of said fragments.

Claim 14

In a speech transmission system, means to analyze speech message currents into a plurality of slowly varying currents simultaneously existent in a corresponding plurality of separate circuits, distributor means to switch short fragments of said currents to line in rapid rotation, means to separately produce a corresponding plurality of currents each varying in amplitude in time correspondence with the switching rate of said distributor means, and each having random distribution of amplitude among successive switching times, and means to add said separately produced currents individually to the fragments of said slowly varying currents as the latter are switched to line, to mask the identity of said fragments.

Claim 15

A system according to claim 7, including a reentrant coding circuit for reducing by a fixed amount the amplitudes of the currents resulting from addition of said switched fragments and separately produced currents, whenever such resulting currents have amplitudes in excess of a definite magnitude.

Claim 16

In a speech privacy system, means for analyzing speech message waves into fundamental pitch-defining signals and spectrum-defining signals continuously varying in amplitude, means for adding to both of said kinds of signals masking currents of amplitudes varying in a manner unrelated to the message current variations, to produce summation currents of signal plus masking currents, and means to subtract from said summation currents whenever their amplitude is in excess of the maximum signal amplitude a fixed amplitude equal to the maximum signal amplitude, to increase the masking of said signals.

Claim 17

In a speech privacy system, means for analyzing speech message waves into fundamental pitch-defining signals and spectrum-defining signals continuously varying in amplitude, means for adding to both of said kinds of signals masking currents of amplitudes varying in a manner unrelated to the message current variations, to produce summation currents of signal plus masking currents, and means to subtract from said summation currents whenever their amplitude is in excess of the maximum signal amplitude a fixed amplitude equal to the maximum signal amplitude, to increase the masking of said signals.

Claim 24

A secret system of transmission for currents varying in amplitude in accordance with signals comprising means to add thereto masking currents varying in amplitude in a manner unrelated to the signal variations to produce summation currents of signal plus masking currents, means to reduce by a fixed amplitude of said summation currents whenever they exceed the maximum signal amplitude, comprising means to subtract a fixed amplitude equal to the maximum signal amplitude, means to transmit the resulting currents to a receiving point, and means to recover the signal from the transmitted currents comprising means to subtract from the transmitted currents varying currents identical to the masking currents, and means to add a fixed amplitude to those currents resulting from the subtraction of said fixed amplitude from said summation currents prior to transmission.

Claim 25

A secret system of transmission for currents varying in amplitude in accordance with signals comprising means to add thereto masking currents varying in amplitude in a manner unrelated to the signal variations to produce summation currents of signal plus masking currents, means to reduce by a fixed amplitude of said summation currents whenever they exceed the maximum signal amplitude, comprising means to subtract a fixed amplitude equal to the maximum signal amplitude, means to transmit the resulting currents to a receiving point, and means to recover the signal from the transmitted currents comprising means to subtract from the transmitted currents varying currents identical to the masking currents, and means to add a fixed amplitude to those currents resulting from the subtraction of said fixed amplitude from said summation currents prior to transmission.

Claim 26

In a secret signal transmission system in which duplicate records are employed to produce identical masking waves at separated transmitting and receiving points together with means for combining the masking waves with the transmitted and received waves, means for maintaining proper frequency and phase relations between the masking waves at transmitting and receiving points comprising means to record a pilot wave on each record, and means controlled by the pilot wave on each record for governing the reproduction rate of the masking waves from the respective record.

Claim 27

In a secret signal transmission system in which duplicate records are employed to produce identical masking waves at separated transmitting and receiving points together with means for combining the masking waves with the transmitted and received waves, means for maintaining proper frequency and phase relations between the masking waves at transmitting and receiving points comprising means to record a pilot wave on each record, and means controlled by the pilot wave on each record for governing the reproduction rate of the masking waves from the respective record.

Claim 28

A system according to claim 14 including an amplifier for the reproduced masking waves from a said record, and means for automatically controlling the gain of said amplifier by means of the pilot wave recorded on said record.

Claim 29

In a system of secret transmission of signals, a plurality of low frequency signal channels, a corresponding plurality of secret key current sources, a line, rotary distributor means for switching signal currents from said signal channels to said line in rotation, means to simultaneously add to each such switched signal current a respective one of said secret key currents, thereby producing summation currents, and a common reentry circuit between said distributor and said line for reducing by a fixed quantity the amplitude of each summation current in excess of a predetermined maximum.

Claim 30

In a system of secret transmission of signals, a plurality of low frequency signal channels, a corresponding plurality of secret key current sources, a line, rotary distributor means for switching signal currents from said signal channels to said line in rotation, means to simultaneously add to each such switched signal current a respective one of said secret key currents, thereby producing summation currents, and a common reentry circuit between said distributor and said line for reducing by a fixed quantity the amplitude of each summation current in excess of a predetermined maximum.

Claim 31

A receiving circuit for secretly transmitted signals composed of combination of signal and key currents, said circuit comprising a source of duplicated key currents, means to combine said duplicate key currents with the secretly transmitted currents to extract signal currents freed of the key currents, said means comprising distributor means for combining said key currents with received currents in succession, a common output circuit for the combined currents and a reentry circuit in said common output circuit for adding a fixed amplitude current to only certain of the combined currents as required to restore the signals to normal form.

Claim 32

A receiving circuit for secretly transmitted signals composed of combination of signal and key currents, said circuit comprising a source of duplicated key currents, means to combine said duplicate key currents with the secretly transmitted currents to extract signal currents freed of the key currents, said means comprising distributor means for combining said key currents with received currents in succession, a common output circuit for the combined currents and a reentry circuit in said common output circuit for adding a fixed amplitude current to only certain of the combined currents as required to restore the signals to normal form.