US2522893A - Remote-control system - Google Patents

Description

Sept. 19, 1950 E. s. PURINGTON REMOTE-CONTROL SYSTEM 5 Sheets-Sheet 1 Filed April 5, 1945 INVENTOR. E; L 504 J. Pun/V 70 A T TORNEV Sept. 19, 1950 E. s. PURINGTON 2,522,893

REMOTE-CONTROL SYSTEM Filed April 5, 1945 5 Sheets-Sheet 3 INVENTOR. 54 01v J. IOUE/NG ro/v ATTORNEY Sept. 19, 1950 E. s. PURINGTON REMOTE-CONTROL SYSTEM 5 Sheets-Sheet 5 Filed April 5, 1945 W MTM u wh NM. u mw IN V EN TOR.

. Nah QYX flL/JQN 6T UR/NG TON BY #44 A TTOR/VEV Patented Sept. 19, 1950 REMOTE-CONTROL SYSTEM Ellison S. Purington, Gloucester, Mass., assignor, by mesne assignments, to Radio Corporation of America, New York, N. Y., a corporation of Delaware Application April 5, 1945, Serial No. 586,781

Claims.

This invention relates to an improved method of remote control by radio, permitting the independent execution of two control operations. For example, as applied to the control of an airborne craft, it provides for left or right rudder, and also for up and down control of elevation, either independently or in combination.

One feature of the invention is that the system cannot be readily operated by the types of transmitters commonly available. Hence a considerable degree of security is provided.

Another feature is provision for the introduction of irrelevant signals so that unauthorized parties will be confused in making analysis of the system which is being employed.

In the operation of the invention a continuous carrier wave is radiated. This wave is then'modulated by selected ones of four different signal frequencies applied in periodic succession, with substantially a quarter of the operating time devoted to each signaling channel. During selected cyclic periods of allotment of the signals to the multiplex channels alternating currents are built up in corresponding receiver channels, with phase separations by 90 electrical degrees, or multiples thereof. The control operations are determined by the phase relations of the currents by the use of phase comparator circuits.

Fig. 1 shows a form of transmitter;

Fig. 2 shows the first portion of a radio receiver cooperating with the transmitter of Fig. 1;

Fig. 3 shows a tuned type phase comparator system for use with the receiver of Fig. 2;

Fig. 4 shows an aperiodic type phase comparator which can be used with the receiver of Fig. 2, alternative to that of Fig. 3.

Fig. 5 illustrates a generalized method of operation in accordance with my invention.

In Fig. 1, a master carrier wave source I [I is operatively coupled through a capacitor II to a modulated power amplifier 20, which delivers amplified power output to antenna 30, modulated in accordance with the signal pattern impressed upon the control grid of modulator 40. The input circuit for tube 20 includes a choke l2 andv a resistor I4 connecting the control grid to ground. Resistor i4 is shunted by a capacitor lit. The output circuit is fed with direct current anode potential from the source l1, connection being made from the anode through a. chok I9 and the primary winding 2| of an output transformer. The inductance 2! is parallel-tuned by a capacitor 22. One end of the parallel-tuned circuit 2l-22 is connected to ground throug'hja capacitor l8 which is chosen as a low impedance to radio frequency currents and as a virtually infinite impedance to audio frequency currents. The transformer primary 2| is coupled to a secondary which feeds energy to the antenna 30. A cathode resistor l5 connects the cathode and suppressor grid to ground. This resistor is shunted by' a capacitor I6. Screen grid potentia1 is supplied from the source I! through a resistor 23. The screen grid is connected to the cathode through -a capacitor 24.

Through the choke l9 anode potential is als fed to the anode of the amplifier tube 40. This tube is shown as a triode but other types of tubes may be used, of course, if desired. The cathode is connected to ground through a cathode resistor 2t which is shunted by a capacitor 21. The input circuit includes a grid resistor 23 connecting the grid to ground. Connection is also made between the control grid and the slip ring of the commutator 41 hereinafter to be described in more detail.

Four selectable frequency sources 4|, 42,43, 44 are provided, which may be operatively connected to the input of a modulator 40 under the control of relay devices 45 and 46, and in accordance with the operation of a commutator 41, driven by motor 49. The relays 45 and 46 in turn are controlled by key sets 5| and 52, with the former used for example for right or left rudder, and.

might be 52, 64, 56, and 68 kilocycles respectively,

and the commutator device might be rotated at a frequency of revolutions per second. The arrangement of the keys and relays shown provides left-right control of the rudder and at the same binations are possible, namely right, left, up,

down, all individually, or right-up, right-down,

left-up, left-down in combination. When a key is in neutral, there is no operation corresponding to that key. These controls determine the order in which the various frequency sources are impressed upon the modulator 48 by the commutator device 41, and therefore the order at which peaks of energy occur in corresponding receiver circuits to be described later.

In more detail, the key is provided with a moveable contact member 53, and contacts 55, 51. Contact 55 is connected through relay winding 59 and. contact 51 is connected through relay winding 6| 'toground, one side of -battery-63 being grounded. The other side ofithis battery is connected to the moveable key contact. The windings 59 and 6| are on opposite legs of a balanced relay 45 having an armature 61 which is operatively connected by insulating member "69 to moveable blades H, 73 of a double pole double throw reversing switch, with outer contacts 15, 11 joined together and to one terminal of source. 4|, and inner contact 19 connected to one terminal of source 43. The other terminals of sources 4| and 43 are grounded. Spring pressure is exerted opposingl against the-insulator 69 by contacts 1| and:='|3, thus normal-1y centering the relay armatur5l and breaking all contacts when neitherof the windings 59 or 6| are actuated. The contacts H and 13 are connected respectively to segments 85 and 81. "mut'ator 41 has a slipring 89 which iss-wept by The coma brush 93 mounted on a rotary brush arm 9| "driven by a motor 49. The brush, therefore, con- "nects each of the commutator segments in suceession to the slip ring. The segments are insulated from each other, and occupy the four "quadrants of the commutator periphery.

The key 52 for up and down operation, its associated relay 4B and commutator connections are similar to those for key 5| and need not be described in detail, other than to catalog the items.

When the key 52 is moved to the up position con- "tact54' is engaged which energizes the winding 62 on relay 46. 'When the key is moved to the down position contact 56 is engaged which energizes winding 60 on this relay. The contact spring arrangement operated b relay 46 includes movable contacts 12 and 14, outer contacts 16 and '18, and themiddle contact 80.

generators 42 "and 44 are connected to the outer and inner cont-acts similarly to the connections The tone described for generators 4| and 43 and their associated relay contacts. The movable contact f is connected to segment 84 on the commutator 41; while contact 14 is connected with commutator segment 86.

'As previously stated, the slip ring '89 is con- -nected to the input grid of modulator-4D, which is connected to ground through resistor 28. I a result, thesegments 81, B5, B6 and 84 are connected to the modulator 40 in rotary succession, "so that its input is energized in succession from whatever voltages are impressed teadily upon these four segments.

With the choice of right-down control, as indicated, the sequence of this four frequency pat- 'tern' will be f1, f3, f2, f4, which sequence is repeated during each revolution of the brush arm 9| at a speed, say, of 100 revolutions per second.

' It will be clear from the above description that The signifiupon the application of the tone frequencies as modulations in different sequences. If only one of the keys, say key 5|, is actuated then a right indication will be represented by the immediate sequence of frequencies f1 and f3 in that order, while if this key is moved for left indication the frequencies will be is and ii in that order. The key 52 being unactuated no modulation frequencies will be sent out While the brush 93 traverses segments 86 and 84. Other sequences of the tone frequency modulations or frequencies f1, f3, f2 and it may, of course, be transmitted, depending upon the remote control operations: to be performed.

The modulating frequencies are recreated at the receiver by use of an arrangement such as --shown in Fig. 2.

Signals from transmitter antenna 30 of Fig. 1

are received by antenna I00 of Fig. 2, tuned to 0 carrier w-a-ve resonance by radio receiver lfll,

and impressed, either directly or after conversion to an intermediate frequency, upon the control grid of detector H12, preferably of the square law, plate detector type. The output is selectively transmitted through frequency discriminator I05 to energize amplifier I I3 most completely from detected energy or frequencies" corresponding to "transmitter sources 4 "and 43) for right-left con- "trol, and amplifier l'l lmo'st completelyfrom detected energy or frequenciescorresponding to transmitter sources '42 and' 44" for up-downcon- 'trol. After amplification in H3, a further-discriminatorl 'actuatesdetectors [33 and I35 most strongly for the" frequencies corresponding 'to sources 4| and 43. Similarly detectors I34, I36 are most strongly actuated from"so'urces"42 and 44, the received'signal"energy"being "fed through the discriminator Ha. I

These detectors are provided with output'circuits with designs-such as 'tosmooth out the detected outputs to produce 'voltages at'terminals I63; |65,I64, 1660f the frequency corresponding to the rotation of commutator 41, but the relative phases" Of the currents will be determined by the signal sequence. For the transmittercase given,

the voltage peak at terr'ninal*|63 will lead th'evoltage'peak at terminal |65-by90 electrical degrees, at 'l00'cycles per second; while the voltage peak at terminal-1B4 will lag*behind the voltage peak-at terminal |6B*by 90 electrical degrees.

It will be understood by those'skilledin theart "that the choice of frequencies for actuation of the selective circuitsis arbitrary, and need "not conform to What-=is -herein 'illustratively stated. Furthermore the circuits themselves may be modified in design, as for example, by-use of more selective circuits, for the frequenciescorresponding-to transmittersources 4| to '44 and for the output frequencies corresponding to the rotary speed of themotor'49.

In addition to the receiver equipment'of'FigpZ, phase comparators are :required forthe' outp'uts of Fig. 2. Although such devices havebeen shown elsewhere, they A are not-= generally known and two arrangements areliereshown. Fig. 3 shows a transformer type with inputs numbered'to opcondenser [65a to the grid of amplifier triode I10,

which in turn is connected through resistor I65b to ground terminal I61. The impedances of elements I63a, I63b, I65a, I65b are all chosen to be substantially equal at the recurrence frequency, say 100 cycles,.so that the voltage on the grid of triode I leads that on terminal I65, while that on the grid of triode I69 lags behind that on terminal I63 both by 45 electrical degrees.

The cathodes of triodes I69 and I10 are connected together and to the positive end of battery Hi, the negative end of which is connected to ground terminal I61. The plate of tube I69 is connected through resonaht circuit I13, I14 and the plate of I10 is connected through resonant circuit I15, I16 to the positive end of battery I12, the negative end of which is connected to the cathodes of tubes I69 and I10. The resonant circuits are tuned to the frequency of recurrenc such as 100 cycles in the illustrative case. If a convention is adopted that currents are positive in the direction shown, then the currents in coils I13 and I will be in phase provided the grids of tubes I69 and I10 are excited in phase, that is if the voltage at terminal I63 with respect to ground leads the voltage at terminal I 65 with respect to ground by 90 electrical degrees. But if the voltage at terminal I63 lags behind that at terminal I65 by 90 degrees, then the grids of tubes I69 and I10 will differ in phase by 180 degrees, so that currents in resonant inductors I 13, I15 will be oppositely phased. But if voltages on terminals I 63 and I65 are like phased or in phase opposition then the currents in inductors I13, I15 will be difierent in phase by 90 degrees in a positive or in a negative sense.

For the case illustrated, since the transmitter source 4| is connected to the modulator just prior to source 43, and since detectors I33 and I35 are responsive to currents of th frequencies of sources 4| and 43, it follows that the voltage on terminal I63 is leading that on terminal I by 90 degrees, thereby causing the currents in the inductors I13 and I15 to be like phased.

The inductors I 13 and I15 are coupled to a pair of independently operating rectifiers I8I, I82, by means of four secondary windings I11 to I 80 inclusive. Preferably the inductors are equal, the couplings are equal and the mutual inductance between each secondary and its primary is the sam as for any other secondary and its primary. One of the windings, such as I11 is reversely coupled, that is in an opposite sense to the others.

One end of coil I11 is connected to the anode of rectifier I8I the other end of I11 is connected through coil I10 to ground. The cathode of rectifier I8I is connected through resistor I83 to ground. The voltage impressed into this rectifier circuit is proportional to the vector sum of the currents in the coils I13 and I15. On the other hand, one end of coil I19 is connected to the anode of rectifier I82, the other end of coil I19 is connected through coil I 80 and resistor I85 to the grounded cathode of rectifier I82. Here the couplings are such that rectifier I82 is driven in accordance with the vector difference of the currents in the coils I13 and I15. Condensers I84 and I86 are bridged across rectifier output resistors I83 and I85 for reduction of A. C. components in the output. For the case given, with voltage at the terminal I63 leading the voltage at terminal I65 by 90 electrical degrees, the rectified current through resistor I83 will-be greatly in excess of the rectified lcui rer'itl through resistor I85. On the other hand if the-- oppositephaserelation held at the input terminals, the current through resistor "I85 wouldgreatly exceed that through resistor I 83. If,

however, the voltages at terminals 163 and I 65 are like phasedor oppositely phased, then the two currents in resistors I83 and I 85-would be equal. 1

The cathode of tube I8I is connected through resistor I81, to the grid of a triode I90, for con-.- trolling a relay 92. The junction of coil- I and resistor I likewise is connected through resistor I88 to the grid of triode I90. Resistors I 83 and I85 are preferably equal, and resistors I81 and I88 are preferably equal but-of much" greater resistance than resistors I63 and I85.. Condenser I09 may be connected from the grids oftube I90 to the ground line. The anode oiv, tube I 90 is connected through one winding93- of relay 92 to the positive terminal of a battery I9I, the negative terminal of which is grounded. The cathode of tube I90 is connected through 1 resistor I to the positive terminal of battery, I9l, also through resistor I93 paralleled by condenser I94 to ground. Relay 92 is provided with an armature 90 having control over a lever, which. terminates in an insulatingbutton 69 for jointly; actuating two movable contact blades 91 and'98., Between these two contact blades is a stationary contact 96. The spring tensions of the contact; blades are mutually opposed so as to normally hold the armature midway between the .pole; pieces of the relay coils 93 and 94. The armature position is, however, a function of the D. C. current in winding 93, this current beingnor v mally balanced by current through an opposing relay coil 94. A rheostat 95 is in circuit with coil 94 and by adjustment thereof the energiza tion of coils 9 3 and 94 can be brought into mutual balance under the no-signal condition. Thecontact 96 is connected through a battery I99 to terminals of two D. C. motors 200 and-20l, the other terminals of which are connected to .the contacts 91 and 98. I

The constants of the relay circuit are so. chosen that when the grid of I90 is at ground 5 potential, current flo'w through relay coil .,9 3., will hold both contacts 91 and 98 open; will occur when the outputs of the rectifiers 'I8 I',=--i I82 are balanced so that the junction point of resistors I81 and I88 is at ground potential; When, howeventhe current through resistor I83;- exceeds that through resistor I85 due to thevolte 1 age of terminal I63 leading the voltage of ter-' minal I65, then the potential of the grid of tube I90 increases, and increased current in coil 93...

causes contacts 96 and 98 to close, thus driving, motor 200. This causes right operation ofthei; rudder in accordance with operation of key 5L. (Fig. 1)- to right position R. If, however, the key, 5| were at position L, then the voltage at ter,-,

minal I63. would lag behind that'at terminal I6,5,,.;

the current through resistor I85 would exceed, that through resistor I83, and the grid of tube I90 would be negative with respect, to ground.

Under these circumstances, the current through relay coil 93 would be reduced, the armature 90,. being then attracted predominantly bycoil 94,. thus producing a circuit closure throughcontact 91 which operates motor 20I for left rudder control. 1 Freedom from operation by unauthorized types: of transmission will depend uponthe lackof defite. pha e re a io s p at he. input terminalsa '7v ltiamhi .65 'of- Fig-:3. Onlyl; whensthe signals; are: suitablysphaseerehted: will the .rectifiedl outputs; of diodesll 8.l.and.:| 82 differ suflicientlyrto produce, anaeffective changelinthe impedanceiof tube I901. and aresultant. actuation of relay 92.

In Fig: 4 arr-alternative type:oicomparatonds. shown;v with conditions corresponding .to thezvolt l age o;fi terminal ;;|64 lagging.90 electricalv degrees-: with respect to that at terminal I66, as when this; circuitjs connected to correspondingpnumbered terminals of. Fig; .3. This comparator does notrequirertuned circuits, and would be especially. useiuluwhen the recurrent rate is quite. low; In thisx-figure both retarding and advancingmircuits areeemployed. between each input: termination ands-the common ground. These circuits 'are cross-connected to two twin-triodes 2l0 and 2| One;-discharge.path in each of these. tubes? is-arrangedto bev actuated' more strongly than the. other..

Theaphase retarding and advancing circuits: compriseeleinents 202 to 209 inclusive, all of which-"are of thesame impedance at the operatingirequency. Retarding circuit comprising resistor' 202'in series with condenser 203andadvancingcircuit comprising condenser 206 and resistor 201 are connected in parallel between terminals|64 and I68. Similarly retarding circuit comprising resistor 204 in series with-condenser- 205, and advancing circuit comprising condenser- 208 'in series with resistor 209 are connectedin parallel between terminals I66 and I68. The junctionsof elements 202 and 203, and of elements 208'and 209- are connected to the two con-'- trol grids of twin-triode amplifier tube 2l0, and the-junctions of elements 206 and 201, and of elements 204- and 205 are connected to the two controlgrids of twin-triode amplifier tube 2| I. The cathodes of these twin triodes are connected together and to the-positive end of battery 2|2, the negative-end of which is connected to grounded terminal I68. The negative end of battery-H3 is connected to the cathodes, while the positive endof battery 2|3 is connected through resistor- 2 M to the two plates of tube 2l0 and through resistor 2|5 -to the two plates of tube 2| I. These two twin-triodes 2 I and 2| I serve as mixing amplifiers; developing an output plate voltage in accordance with'the vector sum of the voltage impressed -upon the two grids.

For the arrangement given, with the voltage at-ter-minal I66 advanced with respect to that at terminal-164, the-two grids of 2|0 areenergized outof phase, but-the two grids of 2| are energized in phase Therefore a large output voltage develops at the plates of 2| and little or no voltage at the-plates of tube 2l0. If on the other hand,

8.... throngnrr'esistonsn l will .be; muchsgreater. than; that-throughresistor 2|9.. The cathode. ofi rectifier 21.1. .is connected :to .ith'em gridmf relay-tubez226 and. that. of rectifier .222.

is.connected..to the grid of relay tube22l. The?! thevoltage-at terminal I64 should lead that at I terminal |66--by 90 degrees, the tube 2|0-would develop largevoltageand tube 2|| a small voltag.e.= For equal phased or reversed phased inputs; the tubes would produce equal-outputs Although-desirable; it is not necessary that theinput voltagesbe of thesame magnitude.

The plates of tube-2l0 are connected-through condenser -2| 6 to the anode of rectifier 2 |'|,-which inturm is connected through resistor 2|8' to 1 ground; The cathode of rectifier 2|1 is 'connected through resistor 2l0 to ground, and this is: shunted by condenser 220.

Similarly a rectifier outputcircuit is providedfor plate output of tube 2 involving elements 221 -170 225 inclusive. For theconditions shown, with the terminal I66 advanced in phase 'with' .ods.

cathodessof .these rtubescarerconnected together. and through resistor .228: to ground, paralleledbyn condenseri.223.. The:plate .oftriode226 is. con.-.-. nected-throughwinding 230and the plateof'wtri ode '221. through winding. 23 of a balanced relayt 232@,to.the.positive end ofbattery 233,.the negative end of :whichsiseconnected to aground... Re sistorz-234fiis connected .between the positive: end: of battery .233 and the :cathodes of. tubes 226 and rv 154221:- The balanced. relay 232 is providedswitho an armature. 235i and with :armature- controlledt contacts 236 and 231. 'It responds to an:'un-'-:'- balancemfothe currents/through itstwo windings.- Contact 236 is connected through motor 238and contact. 231 is connected through motor 233: to'

thenegative end 'of battery 240, thepositive end of which is connectedto a-stationary contact 2M which intervenes between the movable contacts 236'and 231.

In operation the" circuits have been adjusted so that in the absenceof signals, the tubes 226 and 221' pass little-or no current. When in accordance with operation of key 52 of Fig. l,the transmitter is modulated by source 44 (frequency f4) and immediately thereafter by source 42"(fre quency f2) the receiver produces an A. C. voltage at terminal |66-which leads that at terminal l'64 by electrical degrees. This causes a'large D. currentrto fiow through resistor 224 "and a very small D. C. current to flow through resistor 2|9,- the latter current being zero when the magnitudes of the two A. C, voltagesare equal. Tube 22l with itsgrid more positive thanthat of tube 226, causes-the armature 235 of relay 232 to be drawn to the pole-piece on which winding 23-|"is located,-'- closing the contact 236 andrend'ering motor 238 operative 'toexecute the control called for by key-52. If this key were in-neutral,"then= the two currents would be equal and small; so' that the armature '235' of relay 232 would be in' neutral: For the key52on'position-U,the=reverse phase relation would exist at the inputs'of Fig. 4, and the motor 239 would be actuated. In the event of interference which actuat'es recti'-= fiers 2H and 222 m an equal manner, there'will be no output. By choosing the tubes 226*and 22'! withsquare law characteristics, and provid-- ing a relay with little-backlash, the operation'o'f the system will be made independent 'of the amount of interference of randomhature to-a large degree.

It is evident that while the inventionhasbeen" described on the-basis of amplitudemodulating'- a radio carrier, it can be practiced by other meth- For example, a radio carrier can be fre quency modulated to produce'a plurality of carrier frequency valuesin succession, and the currents" necessary for operating the circuits of Fig.2 may;

be produced by heterodyning the radiated fre'.- quency modulated signals. The frequencies of the series 11- f4 herein'referredto may, there'-" fore, be considered variations of carrier frequency assignments, or astone generator frequenciesyac cording to the design of the apparatus.

In Fig. 5 the use'of frequencies f1, f2, fa, f4 andis is indicated, of which frequency is may becom sidered serviceable only for camouflage purposes. A connection panel 50|' comprises a plurality ofi jacks 502 each connected to one of the frequency respect to terminallill, the-"rectified cmrent usources -or tone generatorst Another series-of jacks 503 is suitably connected to contacts of two keys 504 and 505. Key 504 is illustratively shown as having the function of right and. left steering. Key 505 has the function of up and down steering. For convenience the jacks of the 503 series are labeled a, b, c, d and e. By the use of jumper wires 506 the jacks 502 and 503 may be interconnected in any desired combination. The combinations may be changed from time to time according to a secret schedule. In this manner it will be difiicult for an unauthorized recipient of the signals to analyze the system so as to determine what each signal means. Changes may be made from day to day or at predetermined times during the course of a run so that the difficulty of analysis would be greatly increased.

Key 504 has contacts f to o inclusive and key 505 has contacts to 11 inclusive, arranged in alphabetical order. The interconnections between the key contacts and the jacks a to e inclusive are as follows:

Jack a is connected to movable contact 2'; jack b is connected to movable contact 7c; jack 0 has branched connections to contacts n and y; jack (1 is connected to movable contact if, and jack e is connected to movable contact 1;. Contacts g, o and q are interconnected; contacts h and l are interconnected and are also connected to segment I on a rotary distributor switch 41' similar to distributor 41 in Fig. 1. Contact 1' is connected to segment 2 on distributor 41'; contacts m and p are interconnected; contacts 1' and a: are interconnected; contacts s and w are interconnected and are also connected to segment 3 on distributor 41'; contact u is connected to segment 4 on distributor 41'.

With the key contact connections arranged as shown it is possible to transmit signals for left or right rudder control and for up or down elevator control and these signals may be transmitted singly or together. Whenever they are transmitted singly the camouflage frequency is is transmitted on one segment of the unused half of the distributor 41'. The following table shows the correlation between key contact closures, and the connections from the jacks a, b, c, d, e to the commutator segments I, 2, 3 and 4:

Jack Con- Olosure of contact pairs nections to Segments Operation Key 504 Key 505 1 2 3 4 Right only" fg, hi, jk, mn qr, w: a b c Left only gh, ij, kl, no qr, wz b a c Up only gh, mn Pq, st, 1w, wx c d 2 Down only gh, mn qr, tu. 0w, 11 c e d Right-up... fa, hi, ik. 'nm pg, st, uv, wz a b d e Left-u gh, 1' kl, no P9, st, uv, wa: b a d e Right-down. f0, hi, jk, mu gr, iu, mo, 11/ a b e If Leit-down gh, z'j, kl, no gr, tu, 11w. my I; a e d In connection with the above table, it should be pointed out at this juncture that the keys 504 and 505 are of the type known and used extensively in telephone practice as anti-capacity switches, being of the four-pole double-throw type. Such switches are actuated by a cam roller, and standard keys or switches of this type have the springs carrying contacts i and 7c, and t and 12, under tension such as to hold the corresponding key in a central position. Under these conditions, whenever key 504 is moved to execute Right operation (handle of key 504 moved to the right) contact i is moved to the left by the contact with Z, and. at the same time, because of its tension, the spring carrying contact i moves to the right to establish contact with 7'. The center contact a of course need not move much from the position shown in Fig. 5. A similar explanation is applicable to key 505, so-that the accuracy of the preceding table should now be apparent;

Fig. 5 also shows modifications of receiving arrangements where the comparators 3 I and 32 are fed with filtered output components from the units I33, I35, I34 and I36 with intervening jack panel and jumper wire connections for adapting the signal responses to the permutational arrangement of frequencies which at any time may be set up on the jack panel at the transmitter for assignment to the contacts of keys 504 and 505. The receiver circuit components between the antenna I00 and the terminals I63, I65, I64 and I66 may be the same as shown in Fig. 2, and for this reason such circuit components are not repeatedly shown in Fig. 5. They are indicated in their entirety by the rectangle labeled Circuit arrangement of Fig. 2-. The comparators 3| and 32 correspond respectively with either of the circuit arrangements shown in Figs. 3 and 4. The output circuits for these comparators supply suitable currents for driving the'rudder motors 200,

20a, 238 and 239, the same as is shown in either of the modifications of Fig. 3 and Fig. 4.

So far as the modification of the receiving equipment is concerned the only change indicated in Fig. 5 is that of introducing alternative connections between the filter circuits I33, I35, I34 and I36 and the input circuits 33, 35, 34 and 33 of the two comparators 3| and 32. Jumper wires 31 may, therefore, be used for interconnecting the jacks in suitable combinations, thus facilitating the changing of the permutations for the different controls in accordance with a prearranged schedule. The right, left, up anddown steering controls may, therefore, be made to conform to the intended remote control significance of the signals as transmitted, changes being made from time to time in the permutational arrangement of the tone generator frequencies in order to confuse an unauthorized recipient of the signals.

The frequency allotments to the transmitting distributor segments are subject to a certain number of permutational variations. Thus, for example, assuming that only four frequency selective filters are to be provided at the receiving station, and that the camouflage; frequency is will not be interchanged with any other frequency, then in place of the connection of source h to jack a, either of the sourcesfz, f4 or is may be connected. With each of these substitutions the remaining frequency sources may be allotted to the other jacks in different sequences, making 24 possible permutations. Since a receiving commutator has been found unnecessary, however, the starting point for any sequence of signal elements is not distinguishable. Therefore, only six of the 24 possible permutations are really useful as follows: a v r 1 4; The combinationa'c'condin'g to claim I 2 and source "including means associate'dwith the transmitting vliermu'tation apparatus and withithe receiving apparatus f or f f f f transposing Ithe DOSltlOlflS of .the vsignal elements of each'pair in the sequenc'e of transmission. a b d e 5. In a radio controlled: system foristeering a g 2 f 5 dirigible body, the 'co'mbination-withlmotor means b a d a Jacksio'r Csetting therrudd'er'to eitherlside of aneutral g g a position, of a I'FthFEB-IJQSitiOIIF relay i havingr two 8 10 en'ergizing c'oi1s and contacts for reversiblyz actutin s i UtOIJIIIBBIlSg; lec'tro .itubeztcir'cuit :z-If' desiredpan additional frequency-selective g i g sillectingf and dgtectmgisignalfipulses 2 g gg ggzg f gg 1 ii z ii fgg gf gg of different i requ'encya.:charatcteristics:irecuriing at a fixed rate-and aeknowirrsequence 'which may be usefi as subsmtute for any of the oufler 15 be'change'abl'e to derive? characteristic potentials, i quencles for control purposes t?- the dlsplaced and meanszcontrolle'd'lbyizsaid potentialslfor; diffrequency can be igg ig y zg' ferentiallynactu'ating the; coils: of -saidirelay in gggi ggg i g g g si iz s zg gg 2 2 accordance-witlt'theparticular sequence ofrecep- 3 "tion-f of saidipulses. 2r transmits; are W hzn :i x/ision i s ma e for interchanging five and radlatmg Garner frequency energy g g tlator circuit tor?whichulsaidwmeans;:is-. cou" e or morefrequencies certain of the possible com- :means' forgenerlatingnmodulation 'frequency ienstrainerare:castigated: 250011111111 a ing means :couplingv'saidn as aname n thls manner the m fiecodnilg the generating'imeanswtorsaid,modulatorzrcircuit for nals-byan unauthorized recipient will be still applying pulseslof ,energywofpdifierent. frequem fi F 'cies from said-modulation frequencygenerating Q modlficatlons VHF/611151011 y means to said modulator icir'cuit in sequence at be made f a F m the 1n f a substantially fixed pulse rate-said pulses (being or the foregoingldescription. Such modififia 1011s Jcha-racterized 'byi difierent frequencies 'whichapwillbe understood to be comprehended within the pgar inia predetermined,butachangeable sequence, lscope'of my mv n i'em'otelysituated receiving :andl .demodulating clalm: means,- means forrd-iscriminating'between'difier- A z q f z r'g g 3; sentdemodulation products :of the re'ceived signal 1 y Erna P curren r De a r t pulses which possess said different frequency productive-0f i fi i g radlgn characteristics,Piphaseshifting devices operable energy er me 11 mg m or at a-frequerrcy-zequal:to rtherlsaid pulserateu-and W wave means m'clfldmg fi .-eiTective--to combine said demodulation products, pl dlstnbutor a a keymg devlce 93 l gand-reversiblyoperable.-relay=me ans--suitably cou- "ifiiiliii ii riiiefiifi liqii fifii t5255a15311 "Pied ii g g g gj i sense 0 here ay opera ion is made; epe en 'latmg means, said keying device including means upon sequence: of ,ltheffmodulaitionfifrequency 'to-vary the sequence of the generator connec- Hpulsea *tions, a receiver comprising selective means for The, combination accordingtwclaimGrand discriminating between the respective frequencies including mutually opposed? motor r .rfor the slgnals omgma'ted at Sam transmltter and steering a dirigible rbody, and-circuitscontrolled detecting means P diffierens by said relay means for selectively actuating said uquencies; coupled to said discriminating means motor means thereby to steer said body in a producing Voltages corresponding time tion which is determined by the joint control sig- -quence to the sequence of modulation of said 1 mficance of saidmulseS "Wave by the alternating currents 8. The combination according to claim-61=and Phasedisplacingmean? combination with including a four-channel distributor in said comlecting means for 'comblmng sald Voltages to mutating means and atlleast two pairs Eof contacts 'duce chosen remote control effect in said keying means couplingsaid.secondgener- '2. In a'remote control system transmitting apparatus comprising means for keying and modulating a carrier wave with a' train of recurrent signal elements each element of which is characterized as a predetermined control frequency, a "driven multiplex distributor for transmitting said -signal -elements in repeated sequences in pairs, receiving apparatus including amplifier, discriminator and detector stagesrand circuits for g g including a multi-channeldistributor in- 'said shifting the phase ofcertain low frequency comv V r g :ponents which are products of detection, and cscommutatmgmeans andcmtactsm saldvkeymg ating means to said-modulator to provide 'fOIlthlE transmission of modulationpulses in pairsyseparate-controls for said keying means to separately or combindly transmit one. pulse'pair forzii'ghtleft steeringcontrol upon a dirigible body'and one pulse pair for up-down elevator control upon said body. i .9. "The combination i a'ccor'ding to :claim 6 and ,dphasemompamtor circuits for producing a com means for-feeding modulationfrequencyenergies trol voltage the relative positive polarity of which selectively" t' chanhel components"6f depends upon hether the detection products of commutating means, said channeltwo paired signal elements are combined in phase *components'theh fviictidfling a b gna s agreement or contraphasally 7 as desired 'for rem'ote control purposes and at 3, h bi ti according t 1m 2 d "least-oneof=saidchanne1 components of said comincluding means for interjecting into said train mutatingmeans being selectable totransniit a "of signal elements other signal elements rectifi- "sig lpiilse for camouflage Pu 'D S cationof which is to confuse an unauthorized 10. In a remote control systemfforta s'teerin recipient of the signals. device responsive to carriercurrents modulated 13 in repeated sequence at a constant predetermined rate by at least two currents of different frequencies wherein the time sequence of the modulating currents is altered for control purposes, a frequency discriminator and detector system 'excited by said modulated carrier currents for deriving pulses of A.-C. the pulse frequency of which corresponds to said constant rate and the relative times of occurrence of which change when said sequence is altered, and control apparatus responsive to said pulses of A.-C. for controlling said steering device.

ELLISON S. PURINGTON.

REFERENCES CITED Number 14 UNITED STATES PATENTS Name Date Mirick -1 Aug. 24,1926 Loftin June 24, 1930 Phinney Dec. 27, 1938 Luck Mar. 18, 1941 Koch June 10, 1941 Tunick May 5, 1942 Boswau Aug. 3, 1943 Ganahl Jan. 29, 1946 DeBey Mar. 5, 1946 Kellogg Apr. 2, 1946 Moynihan Oct. 1, 1946

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