Security phone

Claim 2

Apparatus operable with a communication network to provide scrambled communications comprising: means for receiving electrical signals representative of information to be conveyed by lines of said network; said network having a DC electrical signal; means for generating periodic electrical signals at a plurality of frequencies having a predetermined relationship to the range of frequencies of said received electrical signals; said generating means having a first state and a plurality of second states; means for selecting one state for said generating means from among said first state and said plurality of second states; said first state of said generating means providing as an output of said generating means a constant amplitude electrical signal; each of said plurality of said second states providing as the output of said generating means a different frequency of said plurality of frequencies; means, externally provided, for selecting one or more of said second states; means for modulating said received electrical signals with the signals generated by said generating means; means for combining said modulated signal with the DC signal of said network; and means for extracting said DC signal of said network in substantial isolation from said modulated signal as combined therewith to provide electrical power for operating said apparatus from said extracted DC signal subtantially without variation from said modulated signal.

Claim 3

The apparatus of claim 1 further comprising: means for receiving varying amplitude electrical signals from said network; and means for demodulating said signals as received from said network with the output of said generating means.

Claim 4

A scrambled communication system having a plurality of apparatus according to claim 2 as user terminals of said network.

Claim 5

The apparatus of claim 2 wherein the DC potential of said network is limited in available current and said apparatus further comprises means for developing said electrical signals representative of information from acoustic waves and using significantly less than said available limit of current.

Claim 6

The apparatus of claim 4 further comprising means for converting said demodulated signals into acoustic waves.

Claim 7

The apparatus of claim 2 further comprising: a flexible circuit board providing mounting for said apparatus and adapted for insertion into an ordinary telephone handset and for placement within the handle region of said handset; and means for retaining said circuit board within said handset substantially within said handle portion thereof.

Claim 8

The apparatus of claim 6 wherein: said means for receiving electrical signals representative of information receives the electrical signals from the mouthpiece of said handset; and means are provided for selectively amplifying said demodulated electrical signals to provide amplification thereof during the second states of said generating means and to apply the amplified signals to the earpiece of said handset.

Claim 9

The apparatus of claim 1 wherein: said generating means further comprises an oscillator; and said means for selecting one from among said first state and plurality of second states includes a socket adapted to provide the first state for said generating means when no plug is inserted in said socket and a plurality of plugs, each with a different electrical characteristic; each said plug, upon insertion into said socket, being adapted to provide a particular one of said plurality of said second states for said oscillator whereby the frequency of oscillation of said oscillator is determined by the particular plug inserted in said socket.

Claim 10

The apparatus of claim 1 wherein said means for extracting said DC signal is operative to prevent undetected interception of said modulated signal by an extension of said communication network having available thereat the same set of lines.

Claim 11

Apparatus operable with a communication network to provide scrambled communications, said apparatus comprising: means for receiving electrical signals representative of information to be conveyed by a set of network lines; said set of network lines having a common line and a voice transmission line; means for generating periodic electrical signals at a plurality of externally selected frequencies having a predetermined relationship to the range of frequencies of said received electrical signals; means for selecting one of said plurality of externally selected frequencies for said generating means; said selecting means having a plurality of separate frequency determining elements separable from said generating means and separable from each other; means for associating at least one of said frequency determining elements with said generating means to cause the generation of said signals thereby at a corresponding frequency; means for modulating said received information representing electrical signals by the signals generated by said generating means; means operative when none of said frequency determining elements are associated with said generating means for inhibiting frequency characteristic alteration of said received electrical signals by said modulating means; and means for applying said received electrical signals as selectively modulated to said common and said voice transmission lines of said communication network.

Claim 12

Apparatus operable with a communication network to provide scrambled communications, said apparatus comprising: means for receiving electrical signals representative of information to be conveyed by a set of network lines; said set of network lines having a common line and a voice transmission line; means for generating periodic electrical signals at a plurality of externally selected frequencies having a predetermined relationship to the range of frequencies of said received electrical signals; means for selecting one of said plurality of externally selected frequencies for said generating means; said selecting means having a plurality of separate frequency determining elements separable from said generating means and separable from each other; means for associating at least one of said frequency determining elements with said generating means to cause the generation of said signals thereby at a corresponding frequency; means for modulating said received information representing electrical signals by the signals generated by said generating means; means operative when none of said frequency determining elements are associated with said generating means for inhibiting frequency characteristic alteration of said received electrical signals by said modulating means; and means for applying said received electrical signals as selectively modulated to said common and said voice transmission lines of said communication network.

Claim 13

The apparatus of claim 10 further including: means for receiving electrical signals between said common line and a voice reception line of said communication network; means for demodulating said signals received from said communication network by the signals generated by said generating means; and means for inhibiting said demodulating means from substantially altering the frequency characteristics of said received network signals whenever none of said frequency determining elements are associated with said generating means.

Claim 14

The apparatus of claim 11 further including: a variable gain amplifying device having first and second states; said first state of said amplifying device providing an amplification greater than the second state of said amplifying device by an amount corresponding to attenuation in said received information representing electrical signals and said received network signals produced respectively by said modulating and demodulating means; and means for providing the first state of said amplifying device whenever one of said frequency determining elements is associated with said generating means and for providing the second state of said amplifying device whenever none of said frequency determining elements is associated with said generating means.

Claim 15

The apparatus of claim 1 wherein: said means for applying said modulated signal to said network further includes means for coupling said modulated signal into a telephone type handset of a user station of said network; and said means for receiving signals from said network further includes means for coupling the signals to be received from in said network through said handset to said apparatus; said apparatus being a portable unit not requiring direct mechanical connection to said handset to achieve said coupling function.

Claim 16

Apparatus operable to provide scrambled communications for a communication network having a set of input and output lines that comprise a common line, a voice reception line, and a voice transmission line with a DC electrical potential between said transmission and common lines to provide a limited excitation current for an input microphone, said apparatus comprising: an input microphone providing conversion of acoustic waves to electrical signals and using substantially less current than the excitation current provided by said common and transmission lines; a phase shift oscillator providing a substantially sinusoidal output at one of A plurality of frequencies within a range of frequencies; a plurality of externally controlled elements selectively associable with said phase shift oscillator to determine the frequency of oscillation thereof; the output of said phase shift oscillator being a constant signal whenever none of said plurality of elements is associated with said oscillator; means for producing a well shaped square wave in response to the substantially sinusoidal output of said phase shift oscillator; first means for multiplying said microphone electrical signals by said square wave; means for applying an amplified representation of said multiplied signal to said common and said transmission lines; means for receiving signals carried by said common and said reception lines; second means for multiplying said received signals by said square wave; means for selectively amplifying said multiplied received signals operative to provide a first level of amplification whenever one of said frequency determining elements is associated with said phase shift oscillator and operative to provide a second amplification whenever none of said frequency determining elements are associated with said phase shift oscillator; the difference in amplification between said first and second amplifications providing compensation for the attenuation of said first and second multiplying means when operating to provide modulation of said respective microphone and received signals; and means for separating the DC potential between said common and transmission lines in isolation from the signal applied thereto for transmission and operative to provide operating current for said apparatus from the limited current provided by said DC signal.

Claim 17

Apparatus operable to provide scrambled communications for a communication network having a set of input and output lines that comprise a common line, a voice reception line, and a voice transmission line with a DC electrical potential between said transmission and common lines to provide a limited excitation current for an input microphone, said apparatus comprising: an input microphone providing conversion of acoustic waves to electrical signals and using substantially less current than the excitation current provided by said common and transmission lines; a phase shift oscillator providing a substantially sinusoidal output at one of A plurality of frequencies within a range of frequencies; a plurality of externally controlled elements selectively associable with said phase shift oscillator to determine the frequency of oscillation thereof; the output of said phase shift oscillator being a constant signal whenever none of said plurality of elements is associated with said oscillator; means for producing a well shaped square wave in response to the substantially sinusoidal output of said phase shift oscillator; first means for multiplying said microphone electrical signals by said square wave; means for applying an amplified representation of said multiplied signal to said common and said transmission lines; means for receiving signals carried by said common and said reception lines; second means for multiplying said received signals by said square wave; means for selectively amplifying said multiplied received signals operative to provide a first level of amplification whenever one of said frequency determining elements is associated with said phase shift oscillator and operative to provide a second amplification whenever none of said frequency determining elements are associated with said phase shift oscillator; the difference in amplification between said first and second amplifications providing compensation for the attenuation of said first and second multiplying means when operating to provide modulation of said respective microphone and received signals; and means for separating the DC potential between said common and transmission lines in isolation from the signal applied thereto for transmission and operative to provide operating current for said apparatus from the limited current provided by said DC signal.

Claim 18

The apparatus of claim 14 wherein said power separating means includes means for regulating the signal applied to power said apparatus.

Claim 19

The apparatus of claim 15 wherein said means for separating said power further includes; a diode bridge providing a predetermined polarity output in response to said DC signal being of either polarity; and an amplifier providing varying degrees of current shunting between the outputs of said diode bridge in response to a relationship between the potential from said diode bridge and a predetermined potential to regulate the signal between the outputs of said diode bridge; said applying means including said amplifier and means for applying said multiplied signal from said first multiplier to said amplifier to cause variations in the current shunted by said amplifier in response to said multiplied signal from said first multiplier.

Claim 20

Apparatus operable with a communication network to provide scrambled communications comprising: means for receiving electrical signals representative of information to be conveyed by lines of said network; said network having a DC electrical signal; means for generating periodic electrical signals at a plurality of frequencies having a predetermined relationship to the range of frequencies of said received electrical signals; said generating means having a first state and a plurality of second states; means for selecting one state for said generating means from among said first state and said plurality of second states; said first state of said generating means providing as an output of said generating means a constant amplitude electrical signal; each of said plurality of said second states providing as the output of said generating means a different frequency of said plurality of frequencies; means for modulating said received electrical signals with the signals generated by said generating means; means for extracting said DC signal of said network in substantial isolation from said modulated signal as combined therewith to provide electrical power for operating said apparatus from said extracted DC signal substantantially without variation in response to said modulated signal; mEans for establishing a reference signal; and means responsive to said reference signal and said modulated signal for regulating said extracted signal and for applying said modulated signal to said network.

Claim 21

Apparatus operable with a communication network to provide scrambled communications comprising: means for receiving electrical signals representative of information to be conveyed by lines of said network; said network having a DC electrical signal; means for generating periodic electrical signals at a plurality of frequencies having a predetermined relationship to the range of frequencies of said received electrical signals; said generating means having a first state and a plurality of second states; means for selecting one state for said generating means from among said first state and said plurality of second states; said first state of said generating means providing as an output of said generating means a constant amplitude electrical signal; each of said plurality of said second states providing as the output of said generating means a different frequency of said plurality of frequencies; means for modulating said received electrical signals with the signals generated by said generating means; means for extracting said DC signal of said network in substantial isolation from said modulated signal as combined therewith to provide electrical power for operating said apparatus from said extracted DC signal substantantially without variation in response to said modulated signal; mEans for establishing a reference signal; and means responsive to said reference signal and said modulated signal for regulating said extracted signal and for applying said modulated signal to said network.

Claim 22

The apparatus of claim 17 wherein said applying and regulating means further include current shunt.

Claim 23

Apparatus operable with a communication network to provide scrambled communications comprising: means for receiving frequency inverted electrical signals from said network representative of information conveyed by said network in a scrambled form; said network having a DC electrical signal; means responsive to the network DC electrical signal for providing operating power therefrom for said apparatus; means for efficiently utilizing said operating power to generate a periodic electrical signal having a predetermined frequency relationship to the range of frequencies of said received frequency inverted electrical signal; first means responsive to said generated electrical signal and the received, inverted electrical signal for efficiently utilizing said operating power to provide frequency inverting of said received inverted electrical signal to define a non-inverted output signal of readily intelligible information; means for producing an electrical signal representative of information to be conveyed by said network; second means responsive to said produced and generated electrical signals for efficiently utilizing said operating power to provide frequency inversion of the produced electrical signal to define a further frequency inverted electrical signal; and means for applying said further frequency inverted electrical signal to said network for communication of the information contained therein in a scrambled form; said operating power providing means including means for providing said operating power in isolation and substantially without variation from said electrical signal representative of information to be conveyed.

Claim 24

Apparatus operable with a communication network to provide scrambled communications comprising: means for receiving frequency inverted electrical signals from said network representative of information conveyed by said network in a scrambled form; said network having a DC electrical signal; means responsive to the network DC electrical signal for providing operating power therefrom for said apparatus; means for efficiently utilizing said operating power to generate a periodic electrical signal having a predetermined frequency relationship to the range of frequencies of said received frequency inverted electrical signal; first means responsive to said generated electrical signal and the received, inverted electrical signal for efficiently utilizing said operating power to provide frequency inverting of said received inverted electrical signal to define a non-inverted output signal of readily intelligible information; means for producing an electrical signal representative of information to be conveyed by said network; second means responsive to said produced and generated electrical signals for efficiently utilizing said operating power to provide frequency inversion of the produced electrical signal to define a further frequency inverted electrical signal; and means for applying said further frequency inverted electrical signal to said network for communication of the information contained therein in a scrambled form; said operating power providing means including means for providing said operating power in isolation and substantially without variation from said electrical signal representative of information to be conveyed.

Claim 25

Apparatus operable with a communication network to provide scrambled communications comprising: means for receiving frequency inverted electrical signals from said network representative of information conveyed by said network in a scrambled form; said network having a DC electrical signal; means responsive to the network DC electrical signal for providing operating power therefrom for said apparatus; means for efficiently utilizing said operating power to generate a periodic electrical signal having a predetermined frequency relationship to the range of frequencies of said received frequency inverted electrical signal; first means responsive to said generated electrical signal and the received, inverted electrical signal for efficiently utilizing said operating power to provide frequency inverting of said received inverted electrical signal to define a non-inverted output signal of readily intelligible information; means for producing an electrical signal representative of information to be conveyed by said network; second means responsive to said produced and generated electrical signals for efficiently utilizing said operating power to provide frequency inversion of the produced electrical signal to define a further frequency inverted electrical signal; and means for applying said further frequency inverted electrical signal to said network for communication of the information contained therein in a scrambled form; said means for providing operating power further including means for regulating said operating power; and said further inverted signal applying means including means for controlling said regulating means to provide the application of said further inverted signal to said network.

Claim 26

Apparatus operable with a communication network to provide scrambled communications comprising: means for receiving frequency inverted electrical signals from said network representative of information conveyed by said network in a scrambled form; said network having a DC electrical signal; means responsive to the network DC electrical signal for providing operating power therefrom for said apparatus; means for efficiently utilizing said operating power to generate a periodic electrical signal having a predetermined frequency relationship to the range of frequencies of said received frequency inverted electrical signal; first means responsive to said generated electrical signal and the received, inverted electrical signal for efficiently utilizing said operating power to provide frequency inverting of said received inverted electrical signal to define a non-inverted output signal of readily intelligible information; means for producing an electrical signal representative of information to be conveyed by said network; second means responsive to said produced and generated electrical signals for efficiently utilizing said operating power to provide frequency inversion of the produced electrical signal to define a further frequency inverted electrical signal; and means for applying said further frequency inverted electrical signal to said network for communication of the information contained therein in a scrambled form; said means for providing operating power further including means for regulating said operating power; and said further inverted signal applying means including means for controlling said regulating means to provide the application of said further inverted signal to said network.

Claim 27

The apparatus of claim 19 wherein: the first and second means for efficiently providing frequency inversion include first and second solid state multipliers; and means for driving said first and second multipliers With a square wave in response to said generated periodic electrical signal.

Claim 28

The apparatus of claim 21 wherein said generating means includes a phase shift oscillator.

Claim 29

The apparatus of claim 19 wherein said operating power providing means further includes means for compensating for variations in said network DC electrical signal with network characteristics.

Claim 30

Apparatus operable to provide scrambled communications for a communication network having a set of input and output lines that comprise a common line, a voice reception line, and a voice transmission line with a DC electrical potential between said transmission and common lines to provide a limited excitation current for an input microphone, said apparatus comprising: an input microphone providing conversion of acoustic wave to electrical signals and using substantially less current than the excitation current provided by said common and transmission lines; a phase shift oscillator providing a substantially sinusoidal output at one of a plurality of frequencies within a range of frequencies; a plurality of elements selectively associable with said phase shift oscillator to determine the frequency of oscillation thereof; the output of said phase shift oscillator being a constant signal whenever none of said plurality of elements is associated with said oscillator; means for producing a well shaped square wave in response to the substantially sinusoidal output of said phase shift oscillator; first means for multiplying said microphone electrical signals by said square wave; means for applying an amplified representation of said multiplied signal to said common and said transmission lines; means for receiving signals carried by said common and said reception lines; second means for multiplying said received signals by said square wave; means for selectively amplifying said multiplied received signals operative to provide a first level of amplification whenever one of said frequency determining elements is associated with said phase shift oscillator and operative to provide a second amplification whenever none of said frequency determining elements are associated with said phase shift oscillator; the difference in amplification between said first and second amplifications providing compensation for the attenuation of said first and second multiplying means when operating to provide modulation of said respective microphone and received signals; means for separating the DC potential between said common and transmission lines in isolation from the signal applied thereto for transmission and operative to provide regulated operating current for said apparatus from the limited current provided by said DC signal, said separating means including: a diode bridge providing a predetermined polarity output in response to said DC signal being of either polarity; and an amplifier providing varying degrees of current shunting between the outputs of said diode bridge in response to a relationship between the potential from said diode bridge and a predetermined potential to regulate the signal between the outputs of said diode bridge; said applying means including said amplifier and means for applying said multiplied signal from said first multiplier to said amplifier to cause variations in the current shunted by said amplifier in response to said multiplied signal from said first multiplier.

Claim 31

Apparatus operable to provide scrambled communications for a communication network having a set of input and output lines that comprise a common line, a voice reception line, and a voice transmission line with a DC electrical potential between said transmission and common lines to provide a limited excitation current for an input microphone, said apparatus comprising: an input microphone providing conversion of acoustic wave to electrical signals and using substantially less current than the excitation current provided by said common and transmission lines; a phase shift oscillator providing a substantially sinusoidal output at one of a plurality of frequencies within a range of frequencies; a plurality of elements selectively associable with said phase shift oscillator to determine the frequency of oscillation thereof; the output of said phase shift oscillator being a constant signal whenever none of said plurality of elements is associated with said oscillator; means for producing a well shaped square wave in response to the substantially sinusoidal output of said phase shift oscillator; first means for multiplying said microphone electrical signals by said square wave; means for applying an amplified representation of said multiplied signal to said common and said transmission lines; means for receiving signals carried by said common and said reception lines; second means for multiplying said received signals by said square wave; means for selectively amplifying said multiplied received signals operative to provide a first level of amplification whenever one of said frequency determining elements is associated with said phase shift oscillator and operative to provide a second amplification whenever none of said frequency determining elements are associated with said phase shift oscillator; the difference in amplification between said first and second amplifications providing compensation for the attenuation of said first and second multiplying means when operating to provide modulation of said respective microphone and received signals; means for separating the DC potential between said common and transmission lines in isolation from the signal applied thereto for transmission and operative to provide regulated operating current for said apparatus from the limited current provided by said DC signal, said separating means including: a diode bridge providing a predetermined polarity output in response to said DC signal being of either polarity; and an amplifier providing varying degrees of current shunting between the outputs of said diode bridge in response to a relationship between the potential from said diode bridge and a predetermined potential to regulate the signal between the outputs of said diode bridge; said applying means including said amplifier and means for applying said multiplied signal from said first multiplier to said amplifier to cause variations in the current shunted by said amplifier in response to said multiplied signal from said first multiplier.