US2145138A

US2145138A - Multichannel secret communication system

Info

Publication number: US2145138A
Application number: US77435A
Authority: US
Inventors: Jr Paul Saylor
Original assignee: FREDERICK H HAGNER
Current assignee: FREDERICK H HAGNER
Priority date: 1936-05-01
Filing date: 1936-05-01
Publication date: 1939-01-24
Anticipated expiration: 1956-01-24

Description

- Jan. 24, 1939. s JR I 2,145,138

MULTICHANNEL SECRET COMMUNICATION SYSTEM Filed May 1, 1936 a Sheets-Sheet 1 25o voLTs POWER Q UNIT- Z8 52 TYPE /6 42 26 V HI H MWE/VTOR PAL L 6A YLO/P JR.

- Jan. 24, 1 939.

MU LTICHANNEL SECRET COMMUNICATION SYSTEM P. SAYLOR. JR 2,145,138

8 Sheets-Sheet 2 Filed May 1, 1956 1000 VOLTS #15 Afromvzy Jan. 24, 1939. P. SAYLOR. JR

MULTICHANNEL SECRET COMMUNICATION SYSTEM Filed May 1, 1956 8 Sheets-Sheet 3 V UNiT z zs 250 VOLTj PowtR %/l;{ %m ms ATTORNEY Jan. 24, 1939. SAYLQR, JR 2,145,138

MULTICHANNEL SECRET COMMUNICATION SYSTEM Filed May 1, 1936 8 Sheets-Sheet 4 V FM]. 55.

REA-MP REAMP. DEMOD M01).- mlxtn; A.F.AMP.

L n/ DtMon P I? 5 WI WI I I I 4 J K i v 315 316 528 312 r 5PEAKU2 H/S A TTOR/VEY Jan. 24, 1939. P. SAYLOR. JR

' MULTICHANNEL SECRET COMMUNICATION SYSTEM 8 Sheets-Sheet 5 Filed May 1, 1936 Z50 VOLTS UNIT PAUL SAYLO/FJ/P. INVENTOR lcnrrafi/vcr 1 P. SAYLOR. JR

I MULTICHANNEL SECRET COMMUNICATION SYSTEM Filed May 1, 1936 8 Sheets-Sheet 6 HIS A TTORNE 7 Jan. 24, 1939.

P. SAYLOR. JR 2,145,138

MULTICHANNEL SECRET COMMUNICATION SYSTEM Filed May 1, 1936 a Shee'ts-Sheet 7 2- SPEAKER 400 VOLT:

3 0 VOLTS 4 H/S ATTORNEY Jan. 24, 1939. P. SAYLOR. JR

MULTICHANNEL SECRET COMMUNICATION SYSTEM Filed May 1, 1936 8 Sheets-Sheet 8 INPUT FHOIYAUU/O AHR IIIIIII'III/J,

YVU WY Pr PAUL SATLOR JR.

Patented Jan. 24, 1939 PATENT OFFICE MULTICHANNEL SECRET COMMUNICATION SYSTEM Paul Saylor, Jr., San Antonio, Tex, assignor oi fifty percent to Frederick'll. Hagner, San An- I tonio, Tex.

Application May 1, 1936, Serial No. 77,435

. 4 Claims.

This invention relates to a multi-channel secret communication system, and has for one of its objects the production of an efilcient means for setting up, through the medium of a sending unit or sending units, a carrier wave having a characteristic form which -is modulated at frequencies distinguishable to my selective receiving unit only, and which is normally indistinguishable to a conventional receiving system 10 A further object of this invention is the production of a method of transmitting a carrier wave having a characteristic form at indistinguishable frequencies, then receiving the indistinguishable frequencies and re-forming the in- 5 distinguishable frequencies so that they are rendered distinguishable.

Another object of this invention is the production of a multi-channel communication system embodying a sending unit and a receiving unit,

20 wherein a multi-channel communication may be maintained between the sending and the receiving units over a single carrier wave.

Still another object of this invention is the production of an improved electro-vibrating con- 25 denser for creating frequency modulation to provide remote control for the signal pick-up.

Other objects and advantages of this invention, as well as the objects and advantages of certain detail portions of the system will appear throughout the following specification and claims.

As an illustration of the principle embodied in the present invention, a simple explanation is given as follows:-

35 When an orchestra or band is making a broadcast. every individual instrument in the orchestra or band sets up a characteristic frequency or group of frequencies in the nature of sound waves, and these frequencies or sound waves are 40 gathered into the microphone and through suitable mechanism modulated into one carrier wave as a complete unit of sound. The carrier wave is picked up by a receiver and through the medium of the speaker the sound is received by the ear 45 of the listener where the complete unit of sound is broken up into its component parts and enables the listener to distinguish the individual sound or voice of the individual instruments of the orchestra or band which is being broadcast. By

50 keeping this fact in mind, it should be understood that a similar result is accomplished in a different way through the medium of my system. Separate groups of frequencies are produced out of range of the human ear which frequencies are 55 far enough apart from each other to avoid interference, and which frequencies have a proper relationship to the frequencies picked up by the microphone, all of the frequencies being sent out over the same carrier at the same time, the carrier wave then being received and finally broken up and fed to separate distinct channels through a selected speakers, whereby a number of separate and distinct signals transmitted may be secretly and individually transmitted and received through the speakers at the same time. The advantage of my system is to broaden the spectrum in an indirect way of radio frequency broadcasting or transmission, involving all types of electrical signal impulses. This is accomplished by having a I plurality of signal input sources that do not interfere with each other and a receiver having a plurality of reproducers which do not interfere with each other.

As a further example, when a program, such for instance as an orchestral broadcast, is gathcred into a microphone, the composite sound of the various voices of the individual instruments is received by the microphone. In my system, individual microphones will pick up individual program broadcasts and feed these broadcosts to a station where they will be transmitted over a single composite carrier wave. In thecase of a single broadcast where the voices of the instruments are gathered into a single microphone and transmitted in the well known manner, this composite tone or sound is received and reproduced by a single speaker and the human ear will pick up the sound enabling the listener to separate the voices of the various instruments of the single broadcast. In my system, the various individual or separate broadcasts picked up by the separate microphones, after being transmitted by a single carrier wave, will be received through the medium of the single carrier wave and then separated and distributed to separate and distinct speakers 40 in accord with the programs initially picked up a by the separate and individual microphones.

In the drawings:

Figure 1 isa diagram of the frequency modulated oscillator illustrating the circuits for one signal channel and employing. my new electrovibrating condenser and showing the audio-amplifiers in conjunction with the condenser;

Figure 2 is a diagram of the amplitude modulated power amplifiers including its exciting crystel controlled oscillator;

Figure 3 is a diagram somewhat similar to Figure 1, and illustrating a group of typical circuits for a second or additional signal channel;

Figure 4 is a diagram of a third signal channel;

Figure is a diagram showing the receiving circuits embodying two separate radio frequency amplifiers, a demodulating stage, a modulating stage, a frequency modulated oscillator, a constant-frequency oscillator, and a high gain audio amplifier for one channel of reception;

Figure 6 is a diagram showing a group of circuits for a second or other channel, comprising a modulator stage, a frequency modulated oscillator, a constant frequency oscillator, and a high gain audio amplifier and also another channel which is a high gain amplifier to amplify whatever audible frequencies maybe present in the carrier wave itself;

Figure 7 is a diagram of various circuits show-- ing three separate two-stage audio. amplifiers and their power unit,'each amplifier consisting of an input stage and an output stage, also having its separate speaker;

Figure 8 is a general diagram of the receiving circuit, disclosing the wave form that each unit produces;

Figure 9 is a general diagram of the transmitting circuit, disclosing the wave form that each unit produces;

Figure 10 is a diagrammatic view of the electroeach amplifier V vibrating condenser used in connection with my invention;

Figure 11 is a transverse sectional view through the electro-vibrating condenser;

Figure 12 is a top plan view of the electrovibrating condenser.

By the term indistinguishable as used in the following description, it should be understood that the frequencies are other than their natural or original nature. As for instance, when trans-1 mitting audible sound, the frequencies are raised beyond the range of the frequencies to which the human ear may respond, thereby producing a carrier wave that even if it is received, no ordinary audio equipment, loud speakers, etc. will respond to it By referring to the drawings, it will be seen that I employ a sending system, as shown in Figure 9, and a receiving system, as shown in Figure 8. The sending system is shown in detail in Figures 1, 2, 3 and 4, whereas the receiving system is shown in detail in Figures 4 to 6, inclusive. These units may-be multiplied at the will of the operator, and for the purpose of explaining the circuits and system as well as the method employed in connection with the present invention, it is only necessary to explain in detail the typical circuits, method and system employed when using one sending unit and one receiving unit.

Attention is invited particularly to Figure 1, wherein it will be noted that |5 designates a '76- type tube and I5 designates at 42-type tube. A microphone or signal pick-up I1 is grounded, as at 20, and the other terminal of the microphone I1 is connected to a microphone battery 2|, the battery 2| being in turn connected in series with the primary of a microphone transformer l8. The secondary of the microphone transformer I8 is connected in series with a gain control potentiometer Is, one terminal of the potentiometer I8 being grounded, as at 22. The primary, and also the secondary of the transformer l8, are grounded as at 23. The circuit just described constitutes an amplifying circuit for the microphone l1, the elements of which are connected in series. The potentiometer I8 is connected to the control grid 24 of the tube l5 by means of an electrical connection 25. The plate I8 of the tube gushes I5 is connected with the primary of the interstage transformer 25, the other end of the primary being connected in series with the resistor 21, this resistor 21 being also connected to the supply line of the 250 volt power unit 28. A by-pass condenser 28 is placed between the ground and the primary of the transformer 25 which is connected to the resistor 21. The secondary of the transformer 28 is connected in series with the control grid II of the tube l5 the other end of the transformer being grounded and the screen grid 3| is connected to the supply line of the power unit 28. The plate 22 is connected in series to the primary of an inter-stage transformer with a ratio of 1:1. The other side of the primary winding of the transformer 88 is connected to the supply line of the power unit 28. The cathode of the tube It is connected to the resistor 34, the other side of the resistor 34 being grounded. A condenser 85 is connected in parallel with the resister 34. The tube I5 is provided with a cathode connection embodying a resistor 38 and a condenser 31 similarly connected with respect to bias circuit of the tube It. The filaments of both of the tubes l5 and II are connected in parallel with the secondary of the step down transformer 88 and the primary is connected in' parallel with the alternating current supply 38. The circuits above described constitute a conventional two-stage audio amplifier.

The secondary of the inter-stage transformer "is connected in parallel with the electro-magnet 40 of the electro-vibrating condenser 4| and this condenser will be described as to its detail structure in the -following:

An oscillator circuit is employed using a 59- type tube 42. .The screen grid 48 and the suppresser grid 44 of the tube 42 are connected with a tap on a resistor 45. One side of the resistor 45 is grounded, the other side being connected to the supply line of the power unit 28. A by-pass condenser 45 which is grounded is connected to the resistor 45, and also to the supply line of the power unit 28. The plate 41 of the tube 42 is connected to a radio frequency choke 48 which in turn is connected to the supply line of the power unit 28. The control grid 49 of the tube 42 is connected to one side of the condenser 58 and to the radio frequency choke 5|, which in turn is connected to a resistor 52, the other side of the resistor being grounded. The other side of the condenser 50 is connected to an inductance coil 53, and to one side of a variable tuning condenser 54 and also to the stationary plate terminal 55 of the electro-vibrating condenser 4|, which condenser 4| will also be described structurally in the following. The opposite side of the inductance coil 53 is grounded and a tap approximately one-third of the distance from the ground is attached to the coil and forms a connection with the cathode of the tube 42. The filament of the tube 42 is connected in parallel with the secondary of the step down transformer 58 and the primary is connected in parallel with the alternating current supply 51. The vibrating diaphragm 58 of the electro-vibrating condenser 4| is connected to the casing thereof, which casing is also grounded.

A coupling coil 58 connects to the negative side of a bias battery 60, the positive end of which is grounded. The opposite side of the coil 58 leads to the connecting wire 6| (note Figure 2), which goes to the suppresser grid 62 of the tube 62 which is of the type RK20.

Figure 3 discloses a second two-stage audio amplifier coupled with a frequency modulated oscillator including a second electro-vibrating condenser.

The various parts are identical in every respect in Figure 3, including the circuits, to that shown in Figure 1, and for .the purpose of identifying the parts, the similar parts are designated by the same numerals with the addition of the letter "a. It should be noted, however, that the bias battery 80a and the coupling coil 59a. in the'circults shown in Figure 3, are connected to the wire 68 which passes to the suppresser grid 80 of the tube 88, which'tube is also of the RK type.

Figures 1 and 3 illustrate the circuit connections I for two or more signal pick-ups within the transmitting system.

Attention is now invited particularly to Figure 2.where it will be noted that C designates a conventional type of crystal controlled oscillator. This oscillator embodies a tube 88 which may be of the 59-type. The screen grid 8'! and the suppresser grid 88 are connected to the tap or the resistor 80, one side of the resistor 69 being grounded and the other side being connected to the supply line of the 500 volt power unit 10, the power unit I0 being grounded as shown. A bypass condenser II having one side'grounded is connected at its other side to the screen and

suppresser grids

81 and 88 of the tube 66. A by-pass condenser I2 having one side grounded, is in turn connected on its ODDOSite side to the supply line of the 500 volt power unit I0. The plate 13 of the tube 86 is connected to the tank inductance coil I4, the other side of which is connected to the supply line of the power unit 10. A tuning condenser I5 is connected in parallel with the tank coil I4. The control grid I8 of the tube 86 is connected to a radio frequency choke I1 and to a crystal I8 which crystal is grounded at its opposite side and the opposite side of the choke I1 is connected to a bias resistor I9, the opposite side of which is grounded, and a condenser is connected in parallel to the bias resistor I9. The cathode of the tube 68 is grounded and the filament of the tube 68 is connected in parallel to the secondary of the step down transformer 8|, the primary of the transformer 8| being connected in parallel to the alternating current supply 82. A,

coupling coil 83 is connected at one side to the tuning condenser 84 which condenser 84 is connected at its opposite side to the plate I3 of the tube 06, the opposite side of the coil 83 being connected to the wire II which feeds a parallel circuit to all of the

control grids

85, 86 and 81 of the tubes I2, 85, and 88.

Radio frequency power amplifier utilizing pentode tubes grounded. The by-pass condenser 95, one sidev of which is grounded, has the other side connected to the choke coil 92. The

control grids

85, 88 and 81 are also connected to the radio frequency choke 88, the other side of which choke is connected to the negative terminal of the bias battery '91 out of which battery the positive terminal is grounded. The

plates

88, 88 and I00 are connected unit. A by-pass condenser I02 having'one side 7 thereof grounded, is connected at its opposite side to this 1000 volt supply line I08. A blocking condenser I0l has one side connected to the

plates

88, 89 and I00 and has its opposite side connected to the tank inductance coil I05 and also to the variable tuning condenser I08 the opposite side of the condenser I08 being grounded. The other side of the inductance coil I05 is connected to the transmitting antenna I01 and also toone side of the variable condenser I08, the opposite side of the condenser being grounded. The filaments of the tubes I2, 65 and 88 are connected in parallel with the secondary of the step down transformer I09 which has a center tap grounded in the conventional manner. It should be noted that two radio frequency by-pass condensers H0 and III are connected in series with each other, the connection common to both condensers being grounded. These condensers that are in series are connected in a parallel circuit with the filaments. The primary of the step down transformer I08 is connected in parallel with the alternating current supply H2.

The frequencies produced by the oscillators in Figures 1 and 3 are in the neighborhood of k. c. or so. However, it is not deslred to limitmy system to this range of frequencies.

Two signal pick-up channels have been described above, and the following is a description of a third signal pick-up channel. The two previously described signal pick-up channels have means for rendering the frequencies indistinguishable and the following signal pick-up circuit produces conventional distinguishable frequencies for modulation upon the power amplifier, the circuits being illustrated in detail in Figure 4.

Attention is now invited in detail toFigure 4 which illustrates a diagram showing a conventional two-stage audio amplifier having thesame characteristic elements as defined with respect to the conventional audio two-stage amplifier in Figure 1, the similar parts being designated by the same numerals having an additional letter designation b. The difference is that the secondary of the inter-stage transformer 33b has one side connected to the negative terminal of the bias battery 80b, the positive terminal of which is grounded. The other end of the secondary 59b of this transformer 33b is connected to the wire I I3. The wire H3 is connected to the suppresser grid Ill of the tube 88, note Figure 2.

In this transmitting'unit, I have illustrated three distinct signal pick-up channels, one channel being illustrated in Figure 1, a second in Figure 3, and-a third in Figure 4. It should be understood that the signal pick-up channel illustrated in the diagram in Figure 4 produces a distinguishable frequency whereas the circuits illustrated in detail in Figure 1 produces a still further indistinguishable frequency. The factor which determines the characteristic frequency nature of the indistinguishable frequency is the variable tuning condenser 58 in the circuit in Figure 1, and 54a in the circuit in Figure3. v

In the diagram, as shown in Figures 1 and 3, it will be noted that the electro-vibrating condensers 4| and la respectively are included so that the frequencies set up by the oscillators in Figures 1 and 3 may be frequency modulated in accord with each respective signal input at the respective signal pick-up.

fact that where condensers are connected in parallel the variation of either will create a change in capacity of both. When this is done,

a change in the frequencies characteristics is accomplished and will be specifically diiferent in each of the circuits shown in Figures 1, Sand 4,

' thereby permitting three separate messages to be 1 receiving antenna I2I, the other side of which is n transmitted over the same carrier wave at one time without interference.

Attention is now invited in detail to Figure 5 V wherein it will be noted that a condenser I 23 is provided, one side of which is connected to the connected to the primary of the antenna coil I22, the other side of the primaryof the antenna coil being grounded with one side; of the secondary. The opposite end of the secondary of the antenna coil I22 is connected to the. control grid I23 of the. type 58 tube I24. A condenser I25 is provided and is in parallel with the secondary of thecoii I22, one side of the condenser I25 being krounded. I The screen grid I26 of the tube I24 connects to theresistor I21, the other side of which is connected to a voltage dividing resistor I23, the other side of the resistor I23 connecting to the 250 volt supply line of the power unit I23, the power unit being also. grounded. A bypass condenser I33 is connected between the cathode of the tube I24 and the screen grid I26 of the tube I24. The suppresser grid I3I is connected'to the cathode of the tube I24. A bias resister I32 has one side connected to the cathode and the other side is grounded. A by-pass condenser I33 is in parallel with the resistor I32.

The. plate I34 connects to the primary of the radio frequency transformer I35. The other side of the primary connects to the radio frequency choke I36 and theother side of the choke I36 connects to the 250 volt supply line of the power unit. A by-pass condenser I31 connects to the wire between the primary of the radio frequency transformer I and the choke I36, the other side of the condenser I31 connecting to the cathode of the tube I24.

The secondary of the radio frequency transformer I35 is connected to the controlling grid. I

I33 of the 58 type tube I33 and the opposite side of the secondary of the transformer I35 is grounded. A tuning condenser I43 is in parallel with the secondary of the transformer I35, the opposite side of the condenser being grounded. The screen grid I of the tube I33 is connected to one side of the voltage dividing resistor I23. A by-pass condenser I42 is connected between the screen grid HI and the cathode of the tube I33. The suppresser grid I43 of the tube I33 is connected to the cathode of the tube I33 and a bias resistor I44 is connected between the cathode of the tube I33 and the ground, a condenser I45 being in parallel with the bias resistor I44. The plate I46 of the tube I33 connects to the primary of the radio frequency transformer I41, the other side of the primary connecting to one side of the radio frequency choke I43, the other side of the choke I43 connecting to the 250 volt supply line of the power unit I23. A by-pass condenser I43 is connected to the .wire between the primary of the transformer I41 and the choke I43, the other side of which goes to the cathode of the tube I33. The

, frequency amplifier.

filaments of the tubes I24 and transformer I53, the primary of the transformer being connected in parallel to the alternating cur rent supply III. Thetwo tubes I24 and I33 and their circuits constitute a conventional radio The secondary of the transformer I41 has one side connected to the diode plates of the type 237 tube I52, and also to a tuning condenser I53, the other side of which condenser is grounded. The opposite side of the secondary of the transformer I41 goes to the resistor I54, and the opposite side of the resistoris grounded. A coupling' condenser II1 connects to thewire between the secondary of the transformer I41 and the resistor I54 and the opposite end of the'condenser II1 connects to' the control grid I55 of the tube I52. Condensers I56 and I51are additional coupling-condensers which areconnected at one side to the wire between the secondary of the transformer I41 and the resistor I54. The opposite ends of these condensers connect to the wires I53 and I53note Figure 6. The screen grid I63 is connected to the I voltage dropping resistor IN, the other sldeconnecting to the 250 volt supply line: of the power [unit I23. A by-pass condenser I62 connects between the screen grid i63-of ground. The suppresser grid I63 of the tube I52 connects to the cathode of the tube I52 and a bias resistor I64 connects between the cathode of the i3 3 are connected in parallel with the secondary oi the stepdown' the tube I52 and the tube I52 and the ground. A condenser I65 is I in parallel with the resistor I64. The plate I 66 of the tube I52 connects 1 side ofithe condenser being grounded. The tube I62 and the associated circuits constitute a demodulator and a modulator.

One side of the oscillator coil I13 goes to the grid leak resistor HI and grid leak condenser I12, the opposite sides of each being connected together and to the control grid I13 01' the 57 type tube I14. A tuning condenser I15 is in parallel with the oscillator coil I13, one side of the condenser I15 and coil I13 being grounded. The tap on oscillator coil I13 goes to the cathode of the tube I14. The suppressor grid I16 and the screen grid I11 are connected together and to the voltage dropping resistor I13, the other side of which resistor I13 goes to the 250 volt supply line or wire I63 and then to the power unit I23. A by-pass condenser I13 is connected to the screen and suppresser grids I11 and I16 of the tube I14, the other side of this condenser being grounded. The plate I33 of the tube I14 is connected to the coupling coil I3I, the other side of which goes to the radio frequency choke I32. The other side-of the choke goes to the 250 volt supply line through the line I33 which Joins line I63. A by-pass condenser I34 is connected to the wire between the coupling coil III and the choke I32, the other side of the condenser being grounded. The tube I14 and its associated circuits constitute a conventional oscillating circult.

to the coupling coil I61, the other side of which coil I61 is connected to the I 63, the other side of the 250 volt supply line of the One side of the oscillator coil I36 goes to the condenser I95 is connected to the wire between the suppresser and screen grids of the tube I90 and the other side of the condenser I95 is grounded. The plate I99 of the tube I90 goes to the primary ofthe audio step up transformer I91, the other side of the primary being connected to the radio frequency choke I98. which choke is connected at its other side to the supply line I89. The tube I90 and its associated circuits constitute a second conventional oscillating circuit.

The secondary of the transformer I91 is connected at one side to the control grid I98; of the 57 type tube I99, and the opposite end of the primary is grounded and a load resistor 200 is in parallel with the secondary of the transformer I91. The screen grid 20I of the tube I99 is connected to the 'voltage dropping resistor 202, the other side of which resistor 202 is connected to the supply line I89. A by-pass condenser 209 is connected between the screen grid 20I and the ground. The suppresser grid 204 of tube I99 is connected at one side to the cathode of the tube I99 and a bias resistor 205 is connected at one side to the cathode of tube I99, the other side of which resistor 205 is grounded. A by-pass condenser 209 is in parallel with the resistor 205 and is grounded at one side. The plate 201' of tube I99 is connected to the radio frequency choke 209 and the other side of the choke is connected to the supply line I99. Plate 291 goes to the wire 209-note Figures 4 and '7. A by-pass condenser 2| is connected between the plate and the ground. The filaments of the tubes I14, I52, I90 and I99 are all connected in parallel with the secondary of the step down transformer 2'I I, the

' primary of the transformer 2 being in parallel with the alternating current supply 2I2.

Attention is now specifically directed to Figure 6. The control grid 2I9 of the 57 type tube 2I4 is connected to the wire I58. The screen grid 2I5 connects to the voltage dropping resistor 2I9, the other side of'which resistor 2I9 goes to the volt supply line 2" of the power unit 2I8 which power unit is grounded.- A by-pass condenser 2I9 is connected between the screen grid and ground of the tube 2I4. A suppresser grid 220 of the tube 2I4 connects with the cathode of the tube 2I4 and a bias resistor MI is connected between. the cathode of the tube 2I4 and the ground. A condenser 222 is in parallel with the bias resistor 22]. The plate 229 is connected to the coupling coil 224, the other side of the coil being connected to the radio frequency choke 225 which connects to the supply line 2I1. A by-pass condenser 229 is connected to the wire between the coupling coil 224' and the choke 225, and the other side of the condenser is grounded. One side of the oscillating coil 221 connects to the grid leak resistor 228, and grid leak condenser 229, the other ends of the grid leak resistor and condenser being connected together and to the control grid 290 of the type tube 29I. The other end of the oscillator coil 221 is grounded. A tuning condenser 292 is in, parallel with the oscillating coil 221 and is grounded at one side. A tap on the oscillator coil 221 goes to the cathode of the tube 29I. The screen grid 299 and the suppresser grid 294 are connected together and go to the voltage droppin resistor 295, the other end of which resistor 295 is connected to the supply line 2I1. A by-pass condenser 299 is connected to the suppresser grid and screen grid of the tube 29I, one side of the condenser being grounded. The plate 291 of the tube 29I connects to the coupling coil 299, the other side of thecoilbeing connected to the choke 299, and the other side of the choke being connected to the supply line 2I1. The by-pass condenser 240 is connected to the wire between the ciated circuits constitute a modulating circuit and tube 29I and its circuits constitute an oscillating circuit.

An oscillator coll-24I is shown, one side of which goes to the grid leak resistor 242 and the grid leak condenser 249. The opposite side of the grid leak resistor 242 and the condenser 249 are connected together and to the control grid 244 of the 57 type tube 245. The opposite end of the oscillator coil 24I is grounded. A tuning condenser 249 is in parallel with the oscillating coil MI and one side of the condenser is grounded. A tap on the oscillator coil 24I is connected to the cathode of the tube 245. A screen grid 241 and the suppresser grid 248 are connected together and go to the voltage dropping resistor 249, the other side of which goes to the supply line 2I1. A by-pass condenser 250 is connected between the screen grid of the tube 245 and the ground. The plate 25I of the tube 2451s connected to the primary of the audio step up transformer 252, the other side of which goes to the radio frequency choke 259 and the other side ofwhich choke 259 goes to the supply line 2I1.- The tube 245 and its circuits constitute a second oscilv lating circuit.

The secondary of the transformer 252 is connected at one side to the control grid 409 of the 5'? type tube 254, the other side of the secondary being grounded. A load resistor 255 is in parallel with the secondary of the transformer,

254 and the ground. A suppresser grid 259 con-- nects to the cathode of the tube 254. A bias resistor 290 onnects to the cathode of the tube.

254, the other side being grounded. A condenser 29I is in parallel with the resistor 290 and has one side grounded. The plate 252 of the tube 254 connects to the radio frequency choke 299 and the other side of this choke 299 goes to the supply line 2I1. The plate 292 is connected to the wire 294--note also Figure 'I. A by-pass condenser 295 is connected between the plate 292 of the tube 254 and the ground. This tube 254 and its associated circuits constitute a high gain audio amplifier.

Note particularly Figure 6 in conjunction with Figure 5, where it will be seen that the wire I59 goes to the control grid 299 of the 57 type tube 291. The screen grid 299 goes to a voltage dropping resistor 299, the other side of which connects to the cathode of the tube 291. A bias resistor 212 is connected to the cathode of the tube 291 and is grounded at one side. A- condenser 219 is in parallel with the bias resistor 212. The plate 214 is connected to the radio frequency choke 215. The other side of the choke goes to the supply line 2". The plate 214 goes to the wire 219. A by-pa'ss condenser 211 is connected between the plate 214 of the tube 291 and the ground. The filaments of the tubes 2. 29l, 294, Ni and 291 are connected in parallel with the secondary of the step down transformer 219, and the primary is connected in parallel with the alternating current supply 219.

- Attention is now directed particularly to Figure 7. The wire 299 goes to the couplin condenser 299, the opposite side of which goes to the potentiometer 29|,- one side of which potentiometer 29I is grounded, and the rotatable arm of the potentiometer goes to the control grid 292 of the '16 type tube 299-and a by-pass condenser 294 is connected between the control grid 292 and the ground. The cathode of the tube 299 connects to the bias resistor 299 of which the other side is grounded and the bypass condenser 299 is in parallel with the bias resistor 285. The plate 291 of the tube 283 is connected to the primary of the step up audio transformer 29!, the other side of which goes to the 300 volt supply line 299, which line 299 goes to the voltage dropping resistor 299. The other side of the resistor 299 goes to the choke 29l and the other side of the choke goes to one =leg of the filament of the type 83 tube 292. The filter condenser 299 connects to one side of the choke 291 and the other side of the condenser is grounded, and the condenser 294 is connected to the opposite side of the choke 29l and the other side of the condenser 294 is grounded. The by-pass condenser 299 is connected between the supply line 299 and the ground.

4 The secondary of the audio transformer 299 is connected at one side to the control grid 299 for the type 42 tube 291, and the opposite side of the secondary is grounded. The screen grid 299 of the tube 291 is connected to the supply line 299 which goes to the speaker field 999 and the other side of the speaker field goes to a second speaker field 99!. The other side oi. the speaker field 99l goes to a third speaker field 992, and the other side of the speaker field 992 goes to the 400 volt supply line 399. The primary of the output transformer 994 goes to the screen grid 299 and the opposite side is connected to the plate 995 of the tube 291. The cathode of the tube 291 goes to the bias resistor 999, which bias resistor is grounded at its opposite side and the condenser 991 is connected in parallel with the bias resistor 996. The secondary of the output transformer 994 is connected in parallel with the voice coil 999 of the speaker-1. The filaments of the

tubes

299 and 291 are connected in parallel with the secondary of the step down transformer 999, and the primary of the transformer 399 is connected in parallel with the alternating current supply 9". These

tubes

293 and 291 constitute a two-stage audio frequency amplifier establishing one channel of reception.

Speaker-1 is actuated by the

tubes

299 and 291 and their associated circuits. Speaker2 is actuated by tubes 299a and 291a and their associated circuits, the elements of which are designated by the same numerals with the exception of the addition of the letter "a" as described former 9|2. The center tap however, that the coupling condenser 299a is con- .nected directly with the wire 2". It should also be'noted' that the screen grid 299a is connected with the primary of the transformer 994a and w is also connected to the supply line 299. Supply line 299 is connected with'the primary of transformer 299a and also with the resistor 299. The tubes 299a and 29111 constitute a second receiving channel.

Speaker-3 is actuated through the medium of the tubes 2991) and 291i) and the associated circuits which are similar and identical to'the circuits for speaker-l and speaker-2, and the various elements are designated by the same numerals as were applied to speaker-1 and its operating circuits with the addition of the letter "1). The coupling condenser 2991). is connected to the line 219-note particularly Figure 6. The supply line 299 connects to the primary of the transformer 299D. The supply line 299 connects to the screen grid 29912 of the tube 291b and the primary of the audio step up transformer 294b, The speaker-3 and its associated circuits and the associated tubes 29911 and 2911: and their associated circuits constitute a third receiving channel.

It is not desired, however, to limit the number of receiving channels in this invention, as they may be multiplied both as to transmitters and receivers at the will of the builder and operator without departing from the spirit of the invention.

The channel utilizing speaker--3 receives all of the distinguishable impressions upon the carrier wave due to the fact that it is connected through the wire 219 which joins it in Figure 6 to the amplifying tube 261 which tube obtains its input through the wire I99 which wire joins he tube 261 with the wire I59 in Figure 5. The coupling is shown through the coupling condenser I51 as directly connected to the output of the diode detector I92. By coupling at this particular place any distinguishable impression upon the carrier wave is readily picked up. The channels utilizing the speaker-1 and speaker-2 with their respective tubes and circuits as above described, are joined through the

wires

299 and 264 respectively, designated in Figures 6 and 5. Both connections lead to the circuits that reform the indistinguishable impressions that are upon the carrier wave.

The plate 9 of the tube 292 goes to one side of the high voltage secondary of the transformer U2 and the plate 9 goes to the opposite side of the high voltage secondary to the transof the high voltage secondary of the transformer is grounded. The filaments of the tube 292 are "connected in parallel with a step down winding 914 of the transformer M2. The primary of the transformer9l2 isin parallel with the alternating current supply 9 Having thus described all parts and circuits in connection with my invention, I will now describe its operation. r

The transmitting system (note particularly Figures 1 to 4 inclusive) is arranged for transmitting a composite carrier waveunade up of a plurality of individually distinct modulating frequencies. By considering also Figures 5, 6 and '1, it will be noted that means is also provided for receiving the composite carrier wave and splitting up the groups of modulating freamuse quencies in a manner so that they are distributed kind of signal, and it is not desired to limit the present invention to audio transmission and reception.

When speaking into the mike-1 (note Figure 1) with the battery 2| connected, there is set up a varying flow of direct current. In the secondary circuit of the microphone transformerl8 and associated parts (note Figure 1) an alternating current is produced with characteristic form of the pulsating direct current in its primary circuit. This alternating signal is applied to thegrid input 24.0f the tube IS. The cathode bias on tube I5 is produced by bias resistor 88 which is properly by-passed by condenser 31 so as to satisfy the demand of the type '76 tube. The plate current that flows through the primary of transformer 26 which originally was a steady D. C. flowing current from the power unit 28 will vary in accord with whatever signal characteristic is present at grid 24 in tube 15. It will be noted that amplification has also taken place between the input and the output of tube IS. The secondary circuit of transformer 26 picks up the a ternating signal current and produces the characteristic signal in an amplified form upon grid 38 on tube Hi. The proper bias is obtained for tube l6 through the bias resistor 34 which is properly by-passed by condenser 35 so as to satisfy the type 42 tube. The screen grid 3i maintains constant direct current potential from power unit 28. The current passing through the plate 32 is originally a steady direct current which comes through the primary of transformer 33 from power unit 28. This current varies in accord with the characteristic signal input at grid 30 in tube [6. This current is amplified once more. The signal therefore passes from mike1 to the output transformer 33 to the conventional two-stage audio amplifier in the manner just described.

The secondary of the transformer 38 picks up the characteristic signal from the primary of the transformer 33 and supplies it to the electro-magnetic winding 40 of the e ectro-vibrating condenser 4|. As one speaks into the microphone, the signal flowing through the electro-magnet 40 is varied in accord with the operation of the microphone and it is a well known fact that the magnetic field from such an electro-magnet will vary in accord with the signal presented within its winding. The fluctuating magnetic field set up vibrates the metal diaphragm 58 of the electro-vibrating condenser 4!. The results so far produced are mechanical vibrations originally created from remote mike-1. The rest of the e ectro-vibrator 4| will be explained in the following.

The tube 42 is connected in an oscillating circuit supplied from the power unit 28. constant oscillations are created by use of the oscillator coil 53. The tube 42 obtains its correct grid bias, from the bias resistor 52, radio frequency choke 5| being inserted in this circuit to permit radio frequency current from getting into the bias supply. Cathode bias is obtained Steady through the oscillator coil 58. Radio frequency by-pass condenser 58 permits radio frequency currents to pass, but constitutes a bar to direct currents. The screen grid 48 of tube 42 and suppresser grid 44 of tube 42 being connected together obtain their positive potential direct current voltage from power unit 28 through resistor 45. The radio frequency by-pass condenser l4 by-passes to ground all radio frequency currents in the screen grid circuit. The plate 41 of the tube 42 obtains its direct current potential from power unit 28 through radio frequency choke 48, the purpose of this choke being to bar radio frequency from power unit 28. Steady or constant frequency oscillations are created quency within the range at which they are designed to operate may be selected by adjustment of the variable condenser 54. The stationary plate 55 and the vibrating plate 58 are insulated from each other by air as will be hereinafter described. Since plate 55 is stationary and plate 58 is variable, a small minute variable con-' denser is thus provided. This, as shown in the circuits, is connected in parallel with the controlling condenser 54, and it is well known that if either one of the condensers in parallel are changed in capacity the total capacity will be different than their original setting. It is readily seen that the capacity of the electro-vibrating condenser 4| is changed or is varied in accord with the microphone audio pick-up through the medium of the electro-magnet or field of the magnet 40.

Attention is now invited to Figure 3 from which it will be noted that a second channel of signal pick-up is illustrated, the operation of which is identical to that as described and illustrated with respect to Figure 1, with the exception that a frequency controlling condenser 54a is adjustable to a diflerent setting so as to produce a different fundamental characteristic frequency to be used for modulating.

Note particularly Figure 4 which'discloses a two-stage amplifier identical to the circuits embodying the amplifier in Figure 1, in which'the tubes i5 and I8 are comprised and the operation of this circuit is identical to the amplifier circuit comprising the lower portion of the circuit illustrated in Figure l with the exception of course, that the frequency produced by transformer 58b does not actuate an electro-vibrator condenser. This frequency is directly used as one of the modulating frequencies. 1

In Figures 1, 3 and 4, it will be noted that wires Si, 63 and H3, respectively, connect to a separate suppresser grid in one of the radio frequency amplifying tubes i2, and 88, respectively, of Figure 2. These coupling coils 89, 58a and 59b respectively, are in the bias circuits of the three amplifier tubes I2, 85 and. Thebias is furnished by bias batteries 60, 60a and 80b through the coupling coils. Each coupling coil is positioned in proximity to the oscillating coil of each cir cuit in Figures 1 and 3, and in Figure 4 is/placed in proximity to the primary or lowered according to the frequency of the sig- 15. due to this being a typical oscillating circuits since the frequency of this oscillation is deter I nal that is picked up in the coupling coils dueto I7 18 th me' 'm sfm mwesn r,

I "quency in'coupiing coil; 58a m y; be variedbut 'i ;,gatZthei-will Iofthe operatonby adjustment of I 3:xv r b eizon aa -ii mfisu l i he s eui selective flexibflity is mainta n d; aiid shfould the Q ithel phenomena of voltage bucking, the result cbtame b ing: a varyins ias voi ase supp to: each a of the radio frequency power amplifier tubes 7 I2.

.i "and" so as to bias; them separately and van I I y-w ;n m 1rsm ifi di% ma# I j tion' by suppresser'grid modulation which will I 7 bedescribed in a I It is to he noted that I I, 1 in Figure 4 isa: conventicnalmeans of ,mod -r ulating the suppre se and modulation but 'in I i w ll lways have & e j -characteristicjfornrgi in F g s nali putireuuerwyis, used the Output characteristic; frje- I I I '1 1 911 m! d isireia tuning condenser :54 be set i I i I or far irom frequencies obtained in I i;.u're irHI ie 1 7 1 ?s wn inflame 3 supplie an he j nsie :ot fre u cy: wh c ia ways I I l av e the characteristic of the;

' i I 1 names; Zniike2. I

c s d E j ri zure 1: sup lies sfli rther nce} l I or rre uenues seiec esam separated; n 613,

circuit tubes

12,15 and '88; 1 v 1 tlnctfrom the range of frequencies set up in the i l 1 other two channels means: deviatesg in acme a? i v r i emm y u dw th any typ f rid modulation'in'the R. F.'power amplifier producto :produ' frequencies in coupling coil :59; close Q j I g I q I r e c a ie sac of Fig- I I incoming signal; 1

accord I I I On the-0 8 11 1, :the circuit (115% with the, signal input at I I I I I i ing amplitude modulation.

The following is a description of the operation of the crystal control, oscillator and the radio frequency power amplifier shown in Figure 2. In the oscillator tube It and its associated parts and circuits, a pentode crystal oscillator circuit is shown supplied by a power unit 1.. Proper grid bias is supplied by bias grid resistor 19 which is properly by-passed by condenser 80. Radio frequency choke 12 bars radio frequency from the bias supply. The crystal II is cut to vibrate at one certain frequency and is connected in the frequency controlling part of the circuit which is the control grid 18. The cathode 'is grounded providing the negative return, the tube is properly heated, and the proper positive direct current potential is present at the screen grid 01 and suppresser grid 68 of the tube 66. A bypass condenser ll by-passes to ground any radio frequency current present upon the screen grid circuit. An additional by-pass condenser 12 bypasses any radio frequency current which might enter the power unit-an inductance oscillator coil 14 is in the tank circuit of the plate ll of tube i6, and the tuning condenser being in parallel with it furnishes efficient adjustment of this tank coil. Oscillation is set up'in this typical oscillating circuit providing the inductance of coil H and the capacity of condenser 15 is such that a resonant circuit is equal to the frequency of the crystal 18. The oscillation produced is a steady alternating current. This current is picked up by coupling coil 83 and with the use or condenser H the proper amount I is tov the control: grids of;

in parallel; The control is suppliedfby the {bias sha e it ifroni thei bias supply. 1 i I g j radio ifrei n ency current: which,

in u a e we m 186 :is capacity coupled to the plate circuitsot i r j i j i tubes I2. I! and It; by condenser m; f'Ihe'n'eg'a-j' former 39 which 5 d n e 2""; s: h? t n c i i pacity; for the inductancei205;

with thfil sisnafli input: in a antenna c0neienser 108;; current is dependent 7 supplied the radio frequency power amplifier tubes 12; et iand as lwhichiarel connected I I I which :ba'rs' grid: bias to these tuhj-esflfji battery 'iilthrouigh the a .7 radio frequency current w The fllainentsiof the tubes iii and aim i I properly heated and the proper screen grid direct I I f zcurrent potentiaglis maintained nniall threetubes j by a screen grid parallel'connectionandis sup-i I ri e t ro g e ar 'e e y h k "1 d voltage; dropping resistor 83 which in icon -f' nects with the power unit 'AQby-pass can; denser 102; is; solplaced to i a so r-pa s n i m ht enteripower unit as; r The tankcircuitwhich; is'compris'ed ofj 1 1 I 1? bit-pass through conde s rs 1w and m.

rains iire'milemsriaimminer tubesbeing go: the pen .tode type they do i ot reqmre' neiurrauzausn; I I "Pr s n and; 50 a exciting I t0: th nt 'bli 811 8 3:. 8 i 1 i 81, these tubes will transfer? and amplify the ear-- I i glthe adjustment of coni- 1 '1 the br iler Theadiustments I a; resonantnature I v v The tank-circuit will f 5 obtain radio frequency'currentthrbugh the radio II frequencybit-pass condenser: l from the plate iwith jail voltages citing energy; providi tank; circuit will be of; with: the exciting frequency.

and the tuning condenserf I current is the 7 tivei returnior thlsampl'iiier is through the cen- 1 i I v 'tertap on the secondaryjofthe step down; trans i 1:1 sum cient' radio frequency I I f j I;

, The i carrier wave; current is supplied directly to'; j :I i 3 the antenna m by proper adjustment of the operator by adjustment of variable condenser 54 in Figure 1. Referring to Figure 3, wire 83 connects to suppresser 64 of tube 65. The coupling coil 59a supplies the varying bias voltage for the suppresser grid 64. It will also be readily seen that the operator may adjust this varying bias supply by adjustment of variable condenser 54a. Referring to Figure 4, wire H3 connects to the suppresser grid H4 in tube 88. The coupling coil 59b supplies the varying biasing voltages for suppresser grid Ill. It will be readily noted that no control is maintained by the operator outside of the adjusting of the incoming signal at mike-3. A radio frequency carrier wave is set up in the circuits illustrated in Figure 2 of a constant amplitude, the amplitude of which is varied by the circuits and description referred to in Figures 1,

j 'rne aniplitudej bf t isi a; upon the

suppresser bias I I

3 and 4. Each of the tubes I2, 65 and 88 produces The following is the operation of the receiver The incoming carrier wave is picked up by the antenna I2I and is produced in a grid circuit of the conventional radio frequency amplifier tube I24. The associated parts and circuits of tube I24 are of the conventional amplifier design and function in a conventional manner. The composite carrier wave frequency is produced in the primary of the radio frequency transformer I35. The control grid circuit of the tube I39 obtains the composite carrier wave frequency from the secondary of the radio frequency transformer I35. The radio frequency amplifying tube I39 and its associated parts and circuits are of conventional design and function in the conventional manner. The composite carrier wave frequency is produced in the primary of radio frequency transformer I01. In the tube I52 a typical diode rectifying circuit is rier frequency input from the secondary of coil I41. The various impressions upon the composite carrier wave amplitude are produced in the wire H6, due to rectification. Coupling condensers I55, I56 and I51 supply lead wires I59 and I59 with the three rectified frequencies that were originaly used for modulation frequincies in the transmitting circuits. The control grid of tube I52 in its modulating section is supplied with the frequencies just mentioned through the coupling condenser I55.

Discussion will be confined to the reception of one channel of frequencies. In the plate circult of the tube I52, one group of signal frequencies are present in the coupling coil I61. The tube I52 is a double section tube, one section being a diode rectifier, and the other section being a modulator, the associated parts and circuits being of conventional design, and functioning in a conventional manner. The tube I14 is a typical self-controlled oscillating circuit. The various parts of the circuits shown are of a conventional design and operate in a conventional manner. The frequency controling condenser I15 determines the frequency at which this circuit will oscillate. The varying signal current present in the coupling coil I61 will have an effect upon the voltage in the oscillator coil I10 due to proximity of coupling. This will create a frequency deviation in the oscillating frequencies just described. A varying frequency in accord with the signal in coupling coil I61 is produced in the coupling coil NH. The tube I 90 and its associated parts and circuits are in a conventional oscillating circuit and operate in a conventional manner, condenser I9I being the variable condenser that determines the frequency at which the circuit will oscillate. When condenser I9I is adjusted so as to produce a frequency that will equal the frequency condenser I15 has produced by its adjustment,

when no signal is present in coupling coil I 61,-

then a zero beat will be produced in the primary of the transformer I91. The zero beat is obtained by heterodyning two constant frequencies produced by the oscillating tube I14 and I90. When a signal appears in the coupling coil I61 the frequency of the oscillations produced by the tube I14 will deviate. A deviation in frequency of either of the oscillators will no longer result in a zero beat and since the frequency produced by the oscillator tube I90 is constant, the beat signals produced in the primary of the transformer I91 will be equal to the sums and the differences of the two frequencies at any one instant. The sums of the frequencies being useless to this invention due to the fact that the equipment following is not responsive to those frequencies. This leaves only the differences as useful frequencies. As stated in connection with the shown which obtains its car-.

transmitting circuits, the indistinguishable modulating frequencies are varied or deviate in accord with the microphone pick-up. Therefore, the signal current present in the coupling coil I61 varies in accord with the microphone pick-up. If this variation is in accord with the microphone pick-up,then the beat frequency produced in the primary of transformer I91 will also vary and be equal to the frequencies picked up by the microphone. The secondary of transformer I91 produces to the grid circuit of the conventional high gain audio frequency amplifying tube I I9 a signal of audible frequencies. The associated parts and circuits in connection with the tube I99 are of conventional design and function'in a conventional manner. The lead wire 209 goes to the coupling condenser 290 in Figure 7. This coupling condenser couples the audio frequency output of tube I99 to the control grid input of audio frequency amplifying tube 283. Tube 283 and its associated parts and circuits is a conventional audio frequency amplifier and functions in' a conventional manner. The audio frequency signal is introduced into the primary of the transformer 288, the secondary of transformer 289 feeds the audio signal into the control grid circuit of tube I91. The tube 291 and its associated parts and circuits is a conventional audio frequency amplifier and functions in the conventional manner. The primary of transformer 304 obtains the audio signal in a greatly amplified form. The secondary of the output transformer 304 feeds the voice coil 308 of speaker-1. Speaker1 is a conventional speaker and operates in a conventional manner.

Referring to Figure 5, the circuits disclosed constitute a second receiving channel which may be duplicated, and also a third receiving channel. The second receiving channel made up of tubes 2I4, 29I, 254 and 245, are identical and function in the same manner as the circuits and tubes just mentioned, namely, tubes I52, I14, I90 and I99, respectively. The second receiving channel obtains the input signal through the wire I59 which is connected in Figure 5 to the coupling condenser I56. The signal output in the second receiving channel is sent through wire 264 to the coupling condenser 2800. in Figure 7. The

frequency controlling condensers

232 and 246 are adjustable in the same manner as described above but so as to perform in a manner so that the beat frequency output in the primary of transformer 252 is of the proper audio frequencies. is but one proper adjustment of each condenser. It is shown that each of the receiving channels I and 2 are tunable so as to receive separate and individual microphone pick-ups. Now, referring to Figure '7, the coupling condenser 280a feeds the two-stage audio amplifier which is conven tional, and an exact duplicate of the two-stage rectly above in Figure '7, consisting of the

tubes

291 and 293. The conventional speaker-2 produces the output of this audio frequency amplifier. A third channel is used to reproduce any distinguishable impression upon the composite carrier wave that may be present. Referring to Figure 5, the coupling condenser- I51 feeds the wire I59 which leads to the control grid of the tube 261 in Figure 6. This tube and its associated parts and circuits is a conventional high gain audio frequency amplifier and functions in a conventional manner. The output of this tube goes to the wire 216 which goes to the coupling condenser 280b in Figure 1. This coupling con- It will readily be seen that there audio amplifier just described and located di-- denser feeds the input of a two-stage audio frequency amplifier i. e. tubes 233D and 29122. This amplifier and its associated parts and circuits are conventional and operate in a conventional manner. The conventional speaker-3 reproduces the output in a conventional manner. The conventional power supply for all units and circuits in Figure 7 is shown at the bottom of the diagram and consists of the tube 292 and its associated parts and circuits.

Summary By carefully. considering Figures 8 and 9, it will be noted that general diagrams are shown illustrating the transmitting and receiving system, and for convenience I will describe the passage of an audio wave from the microphone to the loud speaker of the transmission and receiving system as follows:

Referring to Figure 9, sound waves are picked up by the microphone H, a pulsating direct current as described by wave form i is created, the amplifier D amplifies wave form I, and produces an alternating current as shown by wave form 2. The oscillator F creates a constant alternating frequency, as shown by wave form 5. The wave form 2 operates the electro-vibrating condenser E which in turn frequency modulates wave form 5 so as to produce wave form 3. Wave form 3 is constant in amplitude but varies in frequency in accord with wave form 2. Crystal oscillator H creates constant alternating current frequency, as shown by wave form 3. Wave form 3 excites the power amplifier G and the amplified output of amplifier G is of the same frequency as oscillator H. The varying frequency wave form 3 amplitude. modulates power amplifier G so as to produce wave form 4. Wave form 4 is the composite carrier wave of the same frequency as crystal oscillator H and is emitted by antenna I01.

Referring to Figure 8, the composite carrier wave created in Figure 9 is received by the antenna HI, and is of a very weak amplitude shown by wave form 3H). Radio frequency amplifier J amplifies wave form 3! and produces wave form 3 of greater amplitude. Radio frequency amplifier K amplifies wave form 3| i so as to produce wave form 3l2 of still greater amplitude. It is noted that wave form 3l2 has the same identical characteristics that the original composite carrier wave had. Demodulator B rectifies wave form 3| 2 and produces all the impressions that vary its amplitude and is shown by wave form 3I3. Oscillator M creates an alternating current frequency, as shown by wave form 3 and the wave form M3 is of a direct current but pulsates at a fairly high frequency rate. The wave form 3 is frequency modulated through the modulator N by wave form 3i3 and wave form 3l5 is produced as the result. Wave form MS has a constant amplitude but varies in frequency in accord with the modulating signal wave form 3I3. A second oscillator 0 creates an alternating current frequency as shown by wave form 3". The frequency of wave form 3|! is equal to the frequency of wave form 3. When there is no modulating signal wave form 3l3, zero beat is obtained between these two frequencies by method of heterodyning. When frequency modulation takes place in modulator N wave form 3i5 deviates and produces a beat frequency by method of heterodyning with wave form 3i1, in the mixer of demodulator P. The beat frequency created is shown by wave form 3| 6 and is of audio frequency. Audio frequency amplifier R amplifies wave form 3I8 so as to produce wave form 3i8 and actuates the reproducing speaker S, which creates the sound waves.

The above su mary constitutes a description of one channel of transmission and receiving communication. It should be understood that these channels may be multiplied so that a plurality of channels may be utilized for transmission and receiving purposes over the same carrier wave at the same time, the present summary merely being typical of the functioning of the various elements of the transmission and receiving system.

The above summary also constitutes an ideal description of a secret transmitter and receiving system.

By referring to Figures 10 to 12 in detail and by noting the previous description, it will be seen that the particular type of electro-vibrating condenser which I use in conjunction with my system comprises a casing 2 previously described, within which casing 2 are mounted the electromagnets 40 which electro-magnets are insulated from the casing 4i 2. This casing H2 is provided with a binding post 320 which is grounded. The

wires 32l and 322 which lead from the electromagnets 20 pass through the insulated grommets carried by the casing H2 and are connected to the secondary of the transformer 33, such as is indicated in Figure 1 or 33a as is indicated in Figure 3. This transformer constitutes the output of the audio amplifier. A diaphragm plate 58 preferably made of tin or any flexible magnetic material is secured to the top edge of the casing I2 and a non-magnetic plate 55 is spaced from the diaphragm plate 53 by means of an insulated washer or gasket 323. An insulated cap 324 is threaded over the top of the casing 2 to bind the parts in position. A binding post 325 extends through the cap 324 and this is connected to the wire 9, as shown in Figure 1, or 3a as shown in Figure 3, depending upon the circuit in which the electro-vibrating condenser is located.

The electro-magnets comprise preferably iron cores and suitable insulated windings. A magnetic field is set up from the output of the audio amplifier connecting at wires "I and 322. The magnetic field varies in proportion in intensity in accord with the output of the audio amplifier. An intense magnetic field vibrates the diaphragm 53 with greater amplitude causing greater fre quency deviation in the oscillator circuits of Figures 1 and 3. The stationary plate 55 and the vibrating plate 58 are spaced and insulated by the insulated washer 23 so as to produce a large area condenser with small capacity and yet so that the diaphragm plate 53 and plate 55 do not touch each other when vibrating according to suitable adjustments of the audio amplifier. The stationary plate 55 and the vibrating plate 53 are given a coating of high frequency insulating laquer as prevention against becoming a shorted condenser in the event that they should come into contact or become too close together. The space between the diaphragm plate 58 and the plate 35 may be either air filled or constitute a vacuum without departing from the spirit of the invention. The insulating laquer is not placed on the part of the diaphragm 53 that rests upon the easing. It is at this point that the-diaphragm obtains a grounded connection.

Having described the invention, what I chim as new is:

1. An electro-vibrating condenser comprising a casing, electro-magnets mounted within and insulated from said casing, means for energizing said magnets, means for groundingthe casing, means for closing one end of the casing, anelectricaliconnection with saidmeans, and a dia--' phragm of magnetic material adapted to be actuated by said magnets and spaced from said means for closing said casing.

2. An electro-vibrating condenser comprising a casing of conducting material, electro-magnets carried by and insulated from said casing, a closure cap of insulated material removably closing one end of said casing, a conducting plate carried by said cap, a diaphragm of magnetic material spaced from said plate and'grounded upon said casing, insulating means interposed between the diaphragm and the first mentioned plate whereby the diaphragm will be spaced and insulated from said first mentioned plate, and an electrical connection for said first mentioned plate, said diaphragm being of flexible material and free to vibrate between the electro-magnets and said first mentioned plate.

"3. A system of the class described comprising means for setting up and transmitting a carrier wave, a frequency modulated oscillator for producing modulated indistinguishable frequencies in the carrier wave, an electro-vibrating condenser,

a typical two-stage amplifier and a signal pickup, a frequency'controlling circuit actuating said oscillator, an output for said two-stage amplifier, said electr c-vibrating condenser coupling said output of said two-stage amplifier tothe frequency controlling circuit of said oscillator, an input for saidamplifier coupled to the signal pickup unit, a carrier wave receiving and rectifying means, and a carrier wave re-forming means for re-forming the carrier wave and rendering the frequencies distinguishable.

4. A system of the class described comprising means for setting up and transmitting a carrier wave,. a frequency modulated oscillator for producing modulated indistinguishable frequencies in the carrier wave, an electro-vibrating condenser, a typical amplifier and a signal pick-up, a frequency controlling circuit actuating said oscillator, an output for said amplifier, said electro-vibrating condenser coupling said output of said amplifier to the frequency controlling circuit of said' oscillator, an input for said amplifier coupled to the signal pick-up unit, a carrier wave receiving and rectifying means, and a carrier wave re-forming means for re-forming the carrier wave and rendering the frequencies distinguishable.

HAUL SAYLOR. .111.