US1635158A - clement - Google Patents

Description

July 5*, 192,7.

' 1,635,158 g. c LEmEm-r RADIO BROADCAST DISTRIBUTING SYSTEI 'original med oct. 2a. 1924 '1 sheets-sheet 2 u me Q k gg o eq Q .a

July 5 1927.

E. E. CLEMENT RADIO BROADCAST DISTRIBUTING SYSTEM Original Filed Oct. 28, 1924 7 Sheets-Sheet 5 n F@ a. :bmw

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E. E. CLEMENT RADIO BROADCAST DISTRIBUTING sYsrEll Original Filed Oct. 28, 1924 A @Ai RN E. E. CLEMENT RADIO BROADCAST DISTRIBUTING SYSTEI Original Filed Oct. 28, 1924 u Jia 'r sheets-sheet 5 acusa! 0101. 0720 ware p Jul 5 1927.

y E. E. CLEMENT RADIO BROADCAST DISTRIBUTING SYSTEI origina rma oct. 2s, 1924 '1 sheets-sheet 6 .10. A d3 n oms mfr: 4 35m7- w' aac/uwe 160 naa/aro: www -160 NMI/070k l l`,635,l Jul s 1927 E. E. CLEMENT 58 nwro BROADCAST DISTRIBUTING sYsTan A original Filedoct. 28, 1924 '7 sheetspsheat '7' Patented July 5, 1927.

UNITED STATES PATENT OFFICE.

EDWARD E. CLEMENT, OF WASHINGTON, DISTRICT OF COLUMBIA, ASSIGNOR TO EDWARD F. COLLADAY, OF WASHINGTON, DISTRICT 0F COLUMBIA.

RADIO BROADCAST DISTRIBUTING SYSTEM.

Original application led October 28, 1924, Serial No. 746,357. Divided and this application led Jnne 19, 1926. Serial No. 117,13L

My invention relates to systems of radio broadcast distribution, and the present application is a division of my copending applieation, Serial No. 746,357, filed October 28, 1924, which is a continuation in part of my prior Patent No. 1,522,357. This invention has for its object to provide an organization for the broadcasting of intelligence in which orderly distribution may be secured. with maximum eiiiciency. The first characteristic feature of the system is that of sending from each center to the class or order of centers next below it without confusion and with a minimum number of wave lengths. This is accomplished through the useof double modulation, which also en. ables easy change of carrier wave frequency at the intermediate or relaying Stations.

My invention is illustrated in the accompanying drawings, in which:

Fig. 1 is a geographical diagram of the area of the United States divided with respect to standard time, showing stations positioned to form part of a typical distributing system embodying this invention.

Fig. 2 is an enlarged geographical diagram of a. portion of Fig. 1 showing subdivision of distribution in localized or districted areas.

Fig. 3 is a graphical diagram showing the channels of distribution and lines of authority and control in the system of Fig. 1.

Fig. 4 is a. circuit diagram of the same lsystem shown in Figs. 1 and 3.

Fig. 5 is a diagram of a telephone central station with two subscribers stations connected to it and is intended to be read with Fig. 5a.

Fig. 5a is a continuation of Fig. 5 and shows aradio central station and a radio suhscribefs station physically connected therewith through the telephone circuits of Fiw. 5.

6 shows symbolically an arrangement of double modulating and transmitting equipment at the A or master station of the system for matter originating there.

Fig. 7 shows symbolically equipment for the B stations, by means of which the primary ca-rrier waves transmit-ted from the apparatus of Fig. 5 may be demodulated and the intermediate frequency waves or envelope modulated upon a new carrier wave C.

Fig. 8 shows symbolically'apparatus similar to that in Fig. 7, but intended to be located at the local or regional distributin stations C, receiving, therefore, on the wave frequency, transmitting on the D or subscribers frequency.

Fig. 9 shows symbolically a subscribers set adapted to receive on the D frequency, to demodulate the short carrier wave, and then to demodulate the intermediate frequency carrier wave, so as to produce audio waves as its output.

Fig. 10 is a. circuit diagram of the apparatus in Fig. 6.

Fig. 11 is a similar circuit diagram of the apparatus shown in Figs. 7 and 8 which 1s the same in construction and arrangement, but ditl'erently tuned accordino' to the station B or C, at which it is located.

Fig. l2 shows symbolically a central office transmitting set which may be located at A, B or C stations, any or all, for simultaneously transn'iitting the same modulations by means of a short singly modulated carrier wave, and a short double modulated carrier. The single modulation is intended for those outside the system while the double'modulation is distributed through the next lower order of stations.

Referring to the drawings, and particularly to Fig. 1 this is a diagram of the United States of America, divided by lines t, t', and t2 into four divisions marked respectively Eastern standard time, Central time, Mountain time, and Pacific coast time. It happens that the town of Hutchinson, Kansas, is within fifty miles of the geographical center of the United States and hence I have shown this town with three rings around it, and the letter A, indicating the location either of the headquarters or master station of the entire system. In each division there is one station with two rings around it, and marked B". These are the head or master district stations of the several divisions, which under certain conditions vserve as relay stations between the A stations and the other B stations for their respective divisions. Other stations are shown in each division with one ring each, and marked B. These are district stations, and receive either directly from the A stations or on occasion by relaying from the head or master B stations in t eir respective divisions. This illustrates the general manner of distribution, and will be referred to hereinafter.

Fig. 2 shows on an enlarged scale a portion of the eastern standard time division, which may be regarded as one or more districts, as it contains a number of district stations B. The main function of this'igure is to show the relation between the district station and the local or regional distributing centers C. It is to be noted that IVashington, D. C., is the head or master B station in the eastern division, while other towns from Boston to Augusta are shown in Fig. 2 with one ring as ordinary distributing centers each serving a number (which in practice would be very considerable) of outlying local or regional exchange centers marked C. Around each of these local stations or centers C are grouped subscribers. These are not shown on Fig. 2, but are indicated in Figs. 3 and 4, to which reference will presently be made.

In Fig. l, I have shown eight district stations B in the eastern division, ten in the central division, and six each in the moun tain and Pacific coast divisions, or a total of thirty. This of course is illustrative only and not to be taken as nal either in positioning or numerical selection. As a matter of fact it the area of the United States be divided up into substantially equal districts, approximately one hundred district stations B would be a convenient number, but it is doubtful Whether the traic would require this many district stations at first. In Fig. 2 I have shown a larger number of stations in part of the same territory, as B stations, and have related a considerable number of C stations thereto. The location of these is a matter of choice, and they may or may not be associated with local telephone exchanges,

as convenience and traiiic conditions may demand.

For the purpose of a basic description herein of the system as a whole, in the simplest form, I shall assume that each of the three orders of stations, B, C and D, is allotted a single carrier Wave frequency for receiving, which is common to all the stations of the same order, and that say ten intermediate or long Wave frequencies may be modulated thereon, each intermediate frequency being in turn modulated at audio frequencies intended for distribution. At certain times these ten intermediate frequencies may al1 be used at the master station A and broadcasted on the B carrier wave to all the B stations, which in turn will demodulate the initial carrier, amplify and reimpose the same intermediate frequencies and modulations on the common C carrier wave and so relay them to all the C stations, which in turn will demodulate the carrier waves received by them and reimpose the same upon the common carrier Wave alotted to all the D or subscribers stations. At other times there may be only one or two or even none of the intermediate frequencies in use by station A and at such times the unused intermediate frequencies may be allotted to different B stations or even to C stations for local or district broadcasting. In the iirst instance, it will be observed that the original modulations on all the intermediate frequencies are simply passed along by relaying until they reach the' subscribers, who receive them in the original package, so to speak, so that it is entirely possible to say truthfully to the subscribers that they receive and actually hear the original audio modulations, with equal eiiiciency from all points, foreign or domestic; and this in spite of the simplicity of their instruments.

Referring to Fig. 3, the station A is shown connected by lines of distribution to district stations B', B2, B3, and B4. The stations B are in the eastern division, the stations B2 in the central division, the stations B3 in the mountain division, and the stations B'1 in the coast division. Each of these district stations is shown connected by lines of distribution to local distributing stations C in its district, and each of these local stations is shown connected to stations D typifying the ultimate subscribers stations. The lines of distribution also represent telephone trunk lines from C stations to B stations, C represents the subscribers telephone lines which either terminate in station C (if they are identical with telephone exchange stations), or are connected thereto, as indicated in Figs. 5 and 5a.

It will be noted that in Fig. 3 not all the' stations B are connected to station A by direct individual trunk lines, but some district stations trunk through a district master station, thus economizing trunk lines. Thus, the trunks 58, 59 and 60 in Fig. 3 are shown extending to master district stations in the groups B2, B3, and B4 respectively, other B stations in these district groups being connected to A through the respective lnaster stations B by relatively short trunk lines 61. 62 and 63. The number and routing of trunks so used is of course variable, and may be accommodated to the necessities of telephone tratic so as not to interfere with the normal telephonic use of the Wire plant, which is one of the cardinal points in the design of the present system.

A better idea of the general'arrangement of circuits symbolized in Fig. 3 is conveyed by Fig. 4, wherein a subscribers line 18-19 (see Fig. 5) extends from his station D to the central telephone exchange C which is equipped with line jacks J connecting plugs P-P and trunk jacks J 5. From the trunk jack J 5, shown in the figure, a trunk line 50 extends to the district station B, which is also equipped with switchboard terminals including plugs P-PG and trunk jacks J 6, J 7. From the jack J 7 shown in the figure a trunk 5l extends to the masterstation A where it terminates on a jack J 8. The station is equipped with plugs P7--P8, and may be fully provided with telephone switching equipment, like the stations B and C. Details of such switching equipment are shown in Figs. 5 and 5a, the parts being lettered the same in all figures. In Fig. 4, operators telephone instruments are shown at 83. connected in the usual manner to the cord circuit, and these symbolize a complete signaling and supervisory system. Each operator at stations B and A also has a demodulator and receiver for long IF waves, with suitable key for controlling the connection of the same to her cord circuits.

The radio equipment of station C includes a relay receiver and tra-nsn'iitter T with a local microphone and amplifier t2 for local modulation. The ant-enna symbolized at 52 is supposed to receive waves sent out from the B station of the dist-riet in which the particular station C happens to be located, and to which it is connected by means of the trunk line 50, which of course does not symbolize all telephone trunks but only such as may be allotted for the so-called radio traffic. The frequency to which the antenna circuit- 52 is tuned is that allotted to the C stations and to which tliey are all normally or permanently tuned. The antenna circuit 53 is for radiating modulated carrier waves to the subscribers D in the particular local area surrounding and served by the station C under consideration. The frequency to which the antenna 53 is tuned is that al.

lotted to the subscribers D, and to which they are all normally or permanently tuned. The details of the subscribers station apparat-us, including both telephone and radiophone are shown in Figs. 5 and 5a, wherein a particular station of class D is designated as A', and will be described hereinafter. Practically, while the subscribers stations may be used as pickups, regular studio work will probably always be done either through PBX boards with special equipment, or in other special stations connected with a C central station. All of these may be taken as symbolized by the station D or A' in Fig. 4. It should be noted in passing that this allocation of original modulation to C stations does not interfere with direct broadcasting from A or B stations, since each of these can most conveniently be located at and operated in conjunction with a telephone central exchange which is also a C station or has a C station connected to it, as

shown in Figs. 5 and 5a. Thus in Fig. 3 I have shown a microphone transmitter 64 at every stat-ion of the orders A, B and C, to indicate that broadcasting may be originated thereat when required. The actual manner in which this is now intended to be done is shown in Fig. 4. The symbolic station C is provided with a pair of 'jacks J13 and J14 between which are connected the audio amplifier 65 and the intermediate frequency modulator and oscillator transmitter 66. The jacks J13 and J14 may be connected through the operators cords and plugs with the line jack J on the one hand and with either one of the jacks J 4 or J 5 on the other. If jacks J8 and J13 are plugged together and jacks J4 and J14 are plugged together, then the operation would be as follows: Assuming the subscriber A to transmit sound waves electrically over his line 18-19, these waves pass into the audio amplifier 65 and thence into the modulator 66, whereby a modulated intermediate frequency carrier wave is communicated to the input side of the relay transmitter T, which in turn modulates the long wave thus produced upon the short carrier wave allotted to stations D, and radiates the same from the antenna 53. Thus the stat-ion C is broadcasting on the common frequency wave, using an intermediate frequency which the subscribers can receive by double demodulation, in a manner to be presently described.

Now assume that instead of jacks J4 and J14 being plugged up together, the jacks J 5 and J14 are so connect-ed. The result will be as follows: The audio waves over line 18-19 pass to the audio amplifier 65 and thence to the modulator and oscillator transmitter 66, by means of which an audio modulated intermediate frequency carrier current is transmitted over the trunk line 50 to the station B. At this station an arrangement of jacks is encountered similar to that at station C. Jacks J15 and J16 have connected between them an intermediate frequency or carrier amplifier 67 which may be plugged up either for broadcasting from the antenna 55, or for continued transmission over the trunk 51 to the station A. To produce the first result, jacks J 6 and J15 are plugged together and jacks J 9 and J16 are plugged together. whereupon the carrier current or intermediate frequency carrier waves will be communicated to the inputcircuit of the oscillator transmitter B and thereby modulated on a high frequency carrier wave radiated from t-he antenna 55, at standard C frequency. This wave will be received and may be relayed by all the C stations within range of the transmitting station B. If wider distribution be desired the jack J16 is plugged onto the jack J7 of the trunk line 5l, and the amplifier or relayed intermediate frequency carrier waves are transmitted to the station A. Here the arrangement of the intermediate amplifier 68 between the jacks J 11 and J12 is the same as that of the amplifier 67 at station B. By plugging up the jack J12 to the jack J1, the amplified intermediate frequency waves will be communicated to the input side of the oscillator transmitter T2 and thereby modulated on a short carrier wave and radiated Jfrom the antenna 57. As this Wave has a frequency allotted to the B stations, all the B stations will receive it, and may in turn relay it to the C stations and they in turn relay it to their subscribers. One reason for the rule that all broadcast matters shall originate at or through a C station will now be apparent, viz: that the initial audio or telephone Waves may be changed as near as possible to the point of origin to modulated intermediate frequency carrier Waves, which may then be imposed as modulations on a radiated carrier, or on a Wire circuit, with equal eficiency. Audio Waves in a Wire circuit are subject to distortion to a greater degree than modulated superaudio frequency carrier waves. Also, by using superaudio frequency currents on the trunk lines, advantage can be taken of the Well established systems of multiplexing and relaying already in use, and the trunks rendered more productive withoutinterfering with their telephonie use. Thus, the initial audio waves are always changed into modulated superaudio waves at the nearest central station, and thence dispatched either on a carrier Wave radiated from an antenna, or on a trunk wire to some other point where they are so dispatched. In order to add still further to the flexibility of the system, the A station at the right of Figure 4 may trunk as from a jack or jacks J1 through a trunk or trunks to any other part of the system, as for example to a particular B station, Where the trunk may terminate on a jack similar to J, i'or connection t0 radio transmitter T', or by further trunking to some particular C station, and so to the radio transmitter T at such station, whereby matter can be picked up at any point and broadcast either generally or in a selected district or in a sclected local area only. It follows also from this arrangement that when radio transmission is dillicult over long distances or in any particular section of the system, due to seasonal or diurnal or non-periodic phenomena, the distribution by Wire can be made to supplement distribution by pure radio and the average of eliiciency maintained throughout the system. To accomplish this every part of the system must cooperate perfectly with all other parts as determined by the master control station A and district master control stations B, B', etc. both in time of transmission and maintenance of clear transmission channels. Such coordination may be compared to the system of train-dispatching on a railway system, and involves the use of interlocking records and time sheets, for A, B and C stations, and the management and dispatching of all radio trailic by a regular tratlic force trained for that purpose.

Again referring to Fig. 4, it will be observed that station C as Well as stations A and B are indicated as having originating modulators (shown as microphones) 64, which may be plugged onto either the input side of the respective radio broadcast transmitters T. T and T2 or the respective trunks 50, 5l and the trunks from jack J9. At station C the modulating audio transmitter can be operatively connected to either jack J4 0r J5 by inserting plug P in the jack J13 of the ampliiier and long wave modulator and oscillator 66, and then plugging jack J14 to either of the other jacks at will. The parts 65 and 66 are here made separate units because they are common to all subscribers lines as well as the operators microphone circuit. At station B the operators microphone is connected to plug P1o through amplier 69 and long Wave modulator and oscillator transmitter 70; and at station A the operators microphone 64 is connected to plug P11 through amplifier 71 and modulator and oscillator transmitter 72. At station B the trunks 50 bring in modulated intermediate frequency (IF) Waves or carrier current, and in passing this to either transmitter T or trunk wire 51, only amplification is needed, which is supplied by unit 67, which may be a vacuum tube relay as Well as amplilier unit. Similarly at station A the trunks 51 from B stations bring in carrier current or (IF) Waves, and a similar relay and amplifier unit is provided accordingly. Finally, to enable full supervision as Well as reception of audio at each station A, B and C, the operators circuits are indicated as provided with demodulators 72, 74 and 76, and receiving telephones 73, 75 and 77 respectively. These are supposed to be connected to the cords through listening keys respectively, which may also control the connection of ordinary operators telephones 81, S2 and 83, respectively, for telephone conversation over cords, trunks and lines as usual.

It will be understood that Figs. 3 and 4 are merely outlines or skeleton diagrams, in which the metallic line and trunk circuits with all their minutiae of line and cut oli relays, etc., are represented by single lines, and the subscribers and central oice apparatus is all indicated by elementary symbols; but are intended to represent fully developed and equipped standard lines and stations, as shown for example in Figs. 5 and 5a. It may also be noted here that for simplicity of description and illustration I have purposely shown manual rather than automatic telcphone switching apparatus at the exchange centers, but for the attainment of every purpose and the performance of every function in my system which is herein shown attained or performed by manual apparatus, I contemplate as well the use of the corresponding automatic apparatus, as will be further explained hereinafter.

Referring to Figs. 5 ant 5, I have therein shown circuits of the central oiiice and substation equipments and connections, Fig. 5 representing the telephone side of the system, and Fig. 5u the radiophone side of the system. Before proceeding to detail description it may be noted that in accordance with standard telephone practice, provision is made for keeping the telephone lines and central oiice circuits clear of all grounds or other disturbing connections during conversation. lVhen the radiophone goes into service, by closing the filament switch its operation in receiving is identical with that of any radio receiver, and in the event that use is made of any transmission of Waves over the line wires, as will be hereinafter pointed out, said transmission will be at a frequency above the limits of audition. In the present diagram, I have shown the circuits arranged with nothing but continuous current for radio purposes over the telephone line wires. This is the simplest iorm of control and the one nearest to present-day telephone practice, and is absolutely certain not to produce any disturbance in adjacent conductors in the telephone cables. Each radiophone set is provided with a cut olf relay energized when the telephone set goes into commission, either by calling or being called, and at the central otiice whenever the radio operator takes control of the line, he disables it in the usual manner by pulling up the cut ofi' relay at the telephone switchboard, this however being subject to the condition that a special tone test may be put on, so that all operators may know that the line is held on the radio board, and subject to interruption for telephone connection. I prefer to use this tone test only with the radio operators testing plug, because his regular connecting plug includes within its functions that of connecting a subscriber through the station amplitier to the broadcasting transmitting set, and a connection of this character should not be interrupted without permission.

Referring now to the diagram, Fig. 5, A and A are two subscribers stations connccted by line wires 16--17 and 18-19 respectively to the central station C where they terminate on jacks J .and J. 1:-1 are plugs forming the termmals of a cord circuit 20-21, 22-23, having a. bridgedrepeating coil I, ringing and listening keys, supervisory signals s--s and bridging connection to the main battery B. The same battery is shown supplying current to the line relays L, L and through contacts at the cut off relays L2, L3 to the respective lines for calling purposes. In this system, when a subscriber takes down his receiver, the line relay lights its lamp, which is extinguished when the operator inserts the answering plug. Battery supply for the connected lines is thereafter taken through t-he cord circuit 2U-22, 21-23, in a manner well understood in the art. When the suhstation telephones are out of service, with their receivers hanging on their hooks, the line circuits are conductively open for direct current, leaving the ringers Q, and Q in circuit for alternating ringing current passing through the condensers g-g Referring now to Fig. 5a, it will be observed that the radio switchboard which l have designated generally7 by the letter It, is connected to the subscribers lilies by multiple taps marked 16, 17, and 18, and 18, 19, 19'). These terminate on multiple jacks J2, J3, corresponding to the multiple acks on the telephone switchboard. It should be noted that throughout this system the tip wires 16 and 18 with their branches are connected to ground, While the sleeve wires 17 and 19 and their branches are connected to battery. This is extended into t-he radio side of the system for the purpose of securing proper balance between the main battery or power plant of that side and the main battery or power plant of the telephone side of the system.

At the subscribers stations taps are also taken of from the telephone terminals t-o the radiophone terminals as indica-ted at 18C, 19C, and 19". (The radiophone is shown only at one substation for sake of simplicity of illustration.) The two branches 19c and 191 are taken from the sleeve or battery side of the line 19, and are connected to opposite terminals of the winding of a rela L4, which constitutes the substation cut o relay for the radiophone. The Winding of this relay is bridged by a condenser g2 through which both ringing and voice currents can pass Without substantial impedance. Where the radiophone is attached to a party line substation, this relay L4 may be omitted, since on such party lines there are usually grounds on one side or the other. As will presently appear, the radio circuits described herein are applicable to two-party and four-party lines, with individual metering of the party stations.

Tormally, that is to say, when the telephone circuit is not in use, the cut oft relay L4 is deenergized and as a consequence the wire 19 is connected through a back contact of the relay through extension wire 24 to the branch 25 connected to the A battery marked A1 in Fig. 5a. The Wire 18c similarly passes through a back contact of the relay to the extension wire 2G leading to test or listening relay L5 and ground. 185, it will be remembered, leads to tlie tip or ground side of the line, therefore it is the side which in the radiophone can be made use of with a permanent ground or grounds, without disturbing the balance of the telephone circuit.

The radiophone receiver at the substation A is shown as comprising an antenna 23, tuned coupler 29, lirst detector tube 30, tuned h'lter coupler 33, second detector 3l, audio amplier tube- 32, and audio transformers 34, 35, the last mentioned transmitting the amplified audio waves to the telephone receiver or loud speaker 36. The ilamentbattery is A1. The plate battery is B1 and suitable tuning condensers and coils, ticklcr coil for regenerative ei'ects, etc., are provided as required. I should remark in passing that this representation of the radio receiver is intended to be typical only.

The relay L5 has four pairs of contacts, one pair 275 closing the wires 25 and 37 from battery A, to the lilaments. The second pair 275 closes the wires 25 and 38 so as to put battery A1 on the telephone transmitter T, and through the induction coil I, to ground. The third and fourth pairs of contacts 27, 275, close the wires 39 and 40, forming terminals of the secondary induction coil circuit, to the tip and sleeve side of the telephone line respectively, through the back contacts of relay L4. The transmitter T is shown hanging upon a hook switch H controlling the connection of wire 42, constituting a parallel link between the battery A1 and the filament bus 43. Thus the filament can be heated and the radiophone put in service either through the agency of the relay L5, or by the switch hook H. The former is controlled by the radio operator at central and the latter by the subscriber at the substation. In addition to the hook, the subscriber has a manual switch it by which he can connect the battery wire 42 through a Wire 44 to his transmitter T, coil and ground, so as to energize his talking circuit. I provide an ordinary telephone receiver t in series with the secondary of the induction coil I, and I interpose a pair of condensers g3,g4 between the secondary of the induction coil I, and the receiver t on the one hand, and the terminals of relay L5 on the other, so that while the subscriber by means of switch h can connect his phone '--t for receiving calls over the telephone line, he cannot originate telephone calls thereover from the radiophone extension. This is subject to modification by omitting the condensers if desired to originate calls.

Returning now to the central station, and

l particularly to the radio department thereof shown in Fig. 5, T represents a broadcasting transmitter, symbolized in very simple form, but supposed to contain the usual elements of power supply, modulator, oscillator and aerial, with suitable ampliiication of the audio waves supplied on the input side. The jack J 4 connected to the amplifier t2 and thence to the transmitter T, symbolizes a group of such jacks or equivalent connecting means such as automatic switches, controlled by dials or keys for connecting any of the wire lines to said radio transmitter. Detailed appliances, both for the switching and for the radio transmission, are well known in the art, and need no speciic description.

The cord circuit between plugs P3 in Fig. 55 is the saine as the opera'tors cord circuit in Fig. 5, but the radio operator also has special test cords such as that shown in the upper part of the figure connected to plug I. Here the listening and ringing keys are of standard construction, as in the other cords, and the test contact of the plug l)4 is connected through suitable resistance to the supervisory lamp s2 to the radio battery B, means such as the commutator p5 being provided to give special tone test on the test thimbles of the multiple jacks J, J, J 2, etc.

It will be observed that the constant connection of the sleeve or battery wire 24 at the radiophone substation to the bus wire 25 of the battery A1 produces charging of that battery by the constant flow of current therethrough from the main radio battery B at the central office. The amount of energy thus delivered to the battery A1 depends upon the size of the line wires, and the length of time available for such charging. As shown, the battery wire 24 is not cut oli' except when the cut olf relay L4 pulls up which is only when the line Wire is in use for conversation.

Referring now to Figs. 6 to 9 inclusive, I have therein shown the arrangement of receiving and transmitting apparatus at the stations A, B, C and D of Figs. l, 2, 3 and 4. More particularly, these figures constitute a connecting link between Fig. 4 which is merely a skeleton, and the detail circuit figures which follow hereafter. Turning to Fig. 6, I have shown therein an arrangenient of originating broadcast transmitters at the head or master station A. The purpose is double modulation, by first inodulating by means of a telephone transmitter upon a long wave, and then modulating the long wave upon a short carrier wave of suitable frequency to be received at the stations B. It goes without saying, that this same arrangement of apparatus will be found at each of the othercentral stations B and C, being indicated in Fig. 4 by the numeral 6l. In order that this apparatus may also be employed for radio broadcasting of material brought into the stations over wired trunks, I show a jack J1 connected through an aniplilier to switch contacts which may be connected through switch arms to the primary of the transmitter induction coil 302, the secondary of which is connected to the modulator of the generating and transmitting set. Thus a trunk line or even a subscribers wire may be plugged on to the modulator through the amplifier by means of jack J1".

Fig. 7 shows a relay apparatus primarily intended for use at. stations B and C, but which will also be used at master station A. Fig. 8 shows identical apparatus.

The function of the apparatus of Fig. 7 is to take double modulated waves at the frequency allotted to the receiving station, de-

modulate the short wave carrier so as to produce modulated intermediate frequency waves which are then passed through a tuned amplifier 305 to a modulator 306, by means of which they are modulated on a primary or short wave carrier of a frequency suitable for the next lower order of receiving stations, in this case C stations. The short waves thus modulated are then radiated.

By means of the jack 303, intermediate frequency or long waves modulated may be taken ofi' a trunk and passed through the amplifier 305 to the modulator 306 and thence radiated as before. Also, by means of the jack 304 intermediate frequency or long waves modulated which have passed through the demodulator 307 and the amphfier 305 may be forthwith placed upon the wire trunk lines for transmission to other stations. These extensions should be available at each stage in the system, and I consider it original with me to provide means for affecting these combinations of superaudio frequency modulated waves transmitted either from wires to radio carrier or from radio carrier to wires without change either in the intermediate frequency waves or in their modulations, and shall claim the same accordingly. This is one essential feature of the present system, which it is believed should be adhered to in any system of organized broadcasting, i. e. that when an original modulation is once made, the wave train carrying that modulation should be preserved unchanged throughout 1t s entire course from point of origin to the listeners receiver. As described herein, I accomplish this by means of double modulation, with superaudio modulated waves modulated upon the high frequency radio carrier. I shall presently show that single modulated waves can be received and relayed with the same ultimate effect. I consider, however, that the method of double modulation is the best and most perfect for'this purpose.

Referring to Fig. 9, this shows typically a subscribers apparatus for taking double modulated waves sent out from the stations of any of the receding three figures, and demodulating t 1e same so as to recover the original audio modulations and make them apparent. There are two units, one a demodulator of the short carrier wave, which produces the long intermediate frequency wave carrying the original audio modulations, and passes these to the second demodulator, which demodulates the intermediate waves and passes the audio waves to the telephone receiver shown at the right of the figure. This method is shown in detail in F ig. 5a at the subscribers station, where the circuit arrangement of such a double demodulator is illustrated in full.

Fig. 10 illustrates the details of a circuit arrangement which willrealize the functions called for by Fig. 6. Primarily, of course, the purpose of this assemblage of apparatus is to produce double modulation of a primary or short carrier wave, that is to say, to modulate a relatively long wave carrier, and then modulate this long wave upon a relatively short wave carrier which may conveniently be radiated in the usual fashion. Means for receiving and demodulating such double modulated waves have been describcd in connection with Fig. 5a and will be further described herein. In Fig. 10, 150 is a microphone transmitter in a local circuit 151 supplied with energy by battery B4 and containing the primary winding of an induction coil 152, the secondary of which is connected in the grid circuit 153 of the modulator tube 154, said circuit containing a battery Bi. The plate circuit 155 of the tube 154 is bridged by the power battery B and choke coils 157, and is connected through radio choke coil 157a, to the plate of the long wave oscillator tube 158. The plate circuit of the tube 158 contains a' battery B7, which battery is differentially connected to one coil of the coupler 161, which in turn has a wire connection 160 back to the grid circuit. The coupler 161 is tuned on its input side to the long wave frequency supplied by the tube 158, and its secondary winding is connected to the grid circuit of a second modulator tube 162, containing a battery B70. The plate circuit of the tube 162 is bridged by power battery B and choke coil 163, and is connected through the radio choke coil 163a to the grid of the short wave oscillator tube 164. The plate circuit of this tube 164 contains a battery B1 and is connected through a condenser 167a and wire 167 to the antenna circuit, which is also connected back to the grid circuit through wire 166. The antenna circuit 57 is thus supplied with short wave oscillations modulated by the tube 162 with long wave oscillations which in turn have been modulated by the tube 154 with audio modulations due to the primary modulator or microphone transmitter 150. It should be noted that this circuit is an adaptation of the I-Ieising modulator circuit in common use, and it is not claimed herein, being shown for example on page 682 of the work on Principles of Radio Communication by J. H. Morecroft, published by John iViley & Sons, New York, 1921. The use of this apparatus however in combination with other elements to produce theresults stated, and the adaptation of the circuit in question to the purposes of this system, are novel and will be claimed herein.

A modification of this circuit which permits general broadcasting by single modulation, and at the same time double modulation for broadcasting` to subscribers, is indicated in Fig. 12. Here the transmitter 150 is shown working through the induction coil 152 into the modulator designated generally as 154, the oscillator 158 and the modulator 162 into the short wave oscillator 164, all as per diagram Fig. 10. The transmitter circuit 151 however, is branched through a switch 151E to a second coil 1525, by which the same audio modulations are repeated into the modulator 154a and thence into the circuit of the short wave oscillator 164, in this Wa imposing the audio modulations due to t e transmitter 150 directly upon the short carrier wave radiated from the antenna circuit 57. This wave as it goes out will therefore carry both long carrier wave modulations and audio modulations, and the long carrier wave in turn will also carry the .same audio modulations. Receiving devices ot the ordinary type, adapted for single demodula- -tion onl can receive the audio messages conveye in this way. By means of the switch 1515 however, the operator can cut cti' the audio modulator and restrict any part of the broadcast program to the double modulating circuit, for reception only by those who have double demodulating receivers.

The apparatus shown in Figs. 7 and 8 is intended to receive a double modulated carrier wave such as that radiated from the antenna in Fig. 6, demodulate the same and reimpose the long wave or intermediate frequency, with its modulations, upon another short Wave carrier which in the apparatus of Fi 7 as supposed 'to be the carrier wave of a requency allocated to stations C, while in the apparatus of Fig. 8 this is supposed to be the carrier wave of a. frequency allocated to the subscribers stations D. Glaneing at the four figures, (6, 7, 8 and 9), it will be observed that from the original modulation due to the transmitter 150 to the final demodulation by the intermediate wave de modulator in Fig. 9, the same intermediate long wave carrier, and the same audio modula'tions thereof, are maintained intact and unmodified, being merely passed along by relaying from station to station on short carrier waves, or as hereinbefore described on Wiredytrunk lines is the equivalent of the carrier waves.

The apparatus in Fig. 7 and that in Fig. 8 is identical except for the tuning of the transmitted carrier wave. The description of one therefore will sufiice for both.

Referring to Fig. 11, which is a detailed circuit applicable to both these figures, 54 is the receiving antenna coupled at 174 to the grid circuit of the detector 170, whose plate circuit is connected through a. tuned filter coupler 175 to the grid circuit ot the amplifier tube 171, whose plate circuit is connected through the transformer 176 tothe grid circuit of the modulator tube 172, which in turn has the usual Heising connections 178-179 to the circuit of the oscillator tube 173; the radio choke coil 178, the power battery B14 and the magnetic choke coil 177 being arranged as usual. The grid and plate of the oscillator tube 173 are connected to the antenna inductance coil 180, which with the usual tuning condenser 180a is included in the antenna circuit 55. Filament batteries B11, B15, and B15 and plate batteries B12 and B16 are located as usual. As thus described, the assemblage constitutes a relay set which will take in the modulated long waves on a short wave carrier, and retransmit them on a carrier of different frequency, without demodulating or disturbing the modulations of the intermediate or long Wave. In order that these long Waves may be transferred from the first detector circuit to trunks and in order that modulated long waves brought in by trunks may be placed on the radiating antenna 55, I provide connections symbolized as jacks J 9-J 9. The jack J 9 has its springs connected to the terminals of the coupler 175, and these springs normally rest upon contacts in 'the plate circuit of the tube 170. The jack 50 has its springs connected to the terminal of the coupler 17 6, and these springs normally rest on contacts connected in the grid circuit of the modulator tube 172. Trunks such as 50 and 51 terminate on liacks J5 and J7, (see Fig. 4), adapted to be interconnected with each other or with the jacks J 9 and J9 by plugs and cords as indicated at P5 and P5. By plugging either one of the trunk jacks J or J7 onto jack J9, the corresponding trunk line will be connected to the tuned filter coupler 17 5, whose windings are simultaneously disconnected from the detector tube 170. Thus modulated carrier current at the same frequency as the intermediate waves used in the radio side of the system, will come over the trunk line 50, for example, through the jacks J5 and J9 and plugs P5 and P5, and so to the coil 175, whence the long waves will pass to the grid circuit of the amplifier tube 171, to be amplified and then sent through the modulator and oscillator circuits of tubes 172 and 173. Any incoming trunk material can in this Way be put on the air at any station having the relay apparatus of Fig. l1

or the equivalent thereof. For reverse operation, by plugging either one of 'the trunk jacks J6 or J7 onto the jack J9, the corresponding trunk, as 57 for example, becomes connected through plug P and plug P5 to plug .ISO and therethrough to the coil 176, whose primary winding is simultaneously disconnected from the grid circuit of the modulator tube 172. The incoming modulated short carrier waves received on the antenna 54 will pass through the detector 170 and by demodulation of the primary carrier long intermediate frequency waves will be passed through the filter coupler 175,

amplified by the tube 171, and so communicated through the coupler 176 to the cord circuit and jacks, directly to the trunk line 51. In this way, material can be taken off the air at any time and put on the trunks by simply obliterating the primary carrier wave. It is to be understood that by varying the tuning of the couplers, long waves of any frequency can be taken from or fed onto the trunks.

The general operation of the system thus described will now be understood. Ordinarily, items collected, through the system would come into A over the wire trunks and if of general interest, would be passed through from a trunk such as 50 in Fig. 1.1 to the jack J9 and thence through the amplifier, modulator and oscillator to be radiated. This radiation would be in waves of B frequency, and Without other distinctions would be picked up by all the B stations, or at least the head B stations, for relaying, as by their apparatus shown in Fig. 7, to the C stations and thence by means of'theii` relay apparatus such as that s hown in Fig. 8 to the subscribers. In practice there will be a division of such broadcasting, as to items of importance, so as to give them their proper time of distribution in the several divisions of the territory.

As a matter of expediency, the compromise method of regulating the time of a performance of any kind so that it may be broadcasting in all the divisions simultaneously will probably be practiced until the public has become accustomed to an organized system.

The foregoing description, While addressed primarily to broadcasting from station A, includes items drawn from different parts of the system, which implies transmission through B stations from C stations, either by wire or by radio. Matters originating at station A are handled by means of the apparatus of Figs. 6 and 10 but may' also be handled by plugging .the transmitter 64 (Fig. 4) with its amplifier 7 2 and intermediate frequency modulator and oscillator 7l on'toa trunk or trunks 51 leading to B stations, from which the actual broadcasting can be done by connecting trunks to their intermediate Wave amplifiers and the modulators and oscillators of their short carrier waves. (See Figs. 4 and 11.) In other Words, the station A can either broadcast direct or by Wire trunking through the B stations, preferably the head B station of each division. It is further to be noted that the A station when so working over wire trunks can receive the same waves radiated from B or antenna 56 (Fig. 3) and by demodulating and listening to the audio frequency component thereof can determine the eihciency of transmission and the timing of the B apparatus with respect to the short carrier wave employed.

Each station B is supposed to be a district station, that is, it compiles and checks up all bookings or regular number items in its district, keeps the A station informedthereof, makes up district programs, supervises local or C programs including items to be recorded and released later, receives, records and forwards traffic reports and charges from its district to A and acts as a relay station for mixed wire and radio transmission between the C stations in its district and the rest of the system. First, however, the functions of the C stations should be fully understood. These are the stations which come into immediate contact with the subscriber, and which for transmission purposes form their immediate source of supply. So far, as the general broadcasting goes, these stations will be largely considered as they are described in my Patent No. 1,522,357, viz: as relay or distributing stations, each for its own local area. In speaking generally of 'these stations it will be understood that they may or may not be identical with the telephone central stations for the same areas. In the majority of cases each radio C station will be one of a group of telephone exchange stations in its area, and will receive communications from all parts of the area except its own particular territory, by trunking. The functions of each radio exchange C include the following: Relay broadcasting on the subscribers or D carrier wave frequency of program items originating at B or A stations; selection of items and arrangement of local programs to include approved local items if any; listening in and supervising reception by subscribers, using the wire lines for this purpose; connecting subscribers wires or studio wires to trunk lines for direct communication or preferably through amplifier modulator and transmitter units 65 and 66, for superaudio carrier current transmission over trunk lines 50 or to iocal broadcasting transmitters T as indicated in Fig. 5a; and com iling, editing and publishing in the press, y wire, and otherwise, the radio pro rams for the local area served.

Relay fliroadcasting by the C stations would ordinarily be done by means of the apparatus symbolized in Fig 8, which is adapted to double modulation.

For listening in and supervising reception by the subscribers, the radio station C makes use of the apparatus shown in Fig. 5, whereby the waves radiated from the transmitting station may be caused to return after demodulation over the wires so as to be audible to the operator through a proper listening apparatus. The apparatus of Fig. 5a also includes elements such as V, P4, etc. for testing the subscribers line and instrument. If local batteries are employed at the subscribers stations, their condition and voltage can be ascertained and if all current is supplied from central as in my prior applications, Serial No. 699,023, filed March 13, 1924, and Serial No. 722,993, tiled June 28, 1924, then the resistance of the circuits and their proper tuning can be de termined.

For connecting subscribers wires or studio wires to trunk lines for direct or telephonie communication the radio operator has cord circuits and terminals of the lines, symbolized at P3, J3, J2, etc., in Fig. 5a and may have equivalent automatic or semiautomatic switching apparatus. The operation is symbolized in Fig. 4 which shows jacks J and J 5 by means of which the subscriber A can be trunked to any part of the system without going through the telephone switchboard. The typical and preferred mode of trunking by wire in this system, however, is by means of modulated superaudio frequency carrier current which can be interchangeably imposed on the wired circuits or upon suitable radio frequency carrier waves so as to render transmission and interchange over and between the elements of the mixed system both simple and flexible. rThis is accolnplished by first of all modulating the secondary intermediate frequency in accordance with the sounds which it is desired to transmit; and then sending this modulated carrier current over the trunk circuit or circuits to the point where it is to be utilized. Thus, for example, in assuming a trunk connection from the head B stations in Fig. 1 to the master station A, it is taken for granted that the wire trunk lines em loyed for this purpose may be multiplexed1 and provided with tube relays and amplifiers, the same as at present. If more than one intermediate frequency is assigned to the radio broadcasting corporation for use on wired trunk lines, all such frequencies of carrier current might be confined by agreement to the same trunk or trunks, or if a more exible agreement were possible, it might be applied over any trunks in the system. This is not to be confused with telephone trunking broadly, even though it be employed for transmitting sounds from a distance to a radio broadcasting studio. The combination I present is more flexible than that, and at the same time more comprehensive, because it includes all the elements of an organized system, whereby modulated intermediate carriers may be forwarded either by means of wires or by means of double modulated carrier waves, from any point in the system to any other point in thc system, without losses or distortion due to changes in frequency or tuning. It will be remembered that for receiving purposes the instruments at suhscribers stations are all supposed to be standardized, and tuned to one fixed frequency. (This of course is subject to distribution of carrier wave frequencies as expediency may determine and as recommended by the Government. For general purposes it may be assumed here that all subscribers instruments are tuned ixedly for the same primary carrier wave frequency.) In passing through the relay stations however, the primary carrier wave frequencies change from A to B, from B to C, and from C to subscribers D. Thus, if the sending station B should vary the frequency of the C carrier wave transmitted, this would not atleet the intermediate wave frequency or the audio modulations, and so long as C uses the proper frequency D, for the subscribers, the original intermediate waves formed and modulated at the point of origin, would be available in the subseribers tuned local cir.

cuit, the second detector circuit shown in Fig. 5a. On the other hand suppose there be variations in the carrier frequency employed by C in broadcasting to the subscribers station D the subscribers station is shown provided with means to tune the antenna circuit as well as the input circuit of the first tube. Thus the variation in primary carrier wave frequency sent from C could be compensated, but the intermediate wave frequency and the audio modulations thereon are unaffected. As a matter of convenience, subscribers instruments may all be tunable within a certain band of frequencies, to ofi' set any momentary irregularity or variation in transmission wave length from C, as well as to permit reception of single modulated waves. In making use of intermediate frequencies, both by trunking and by double modulation of primary carrier waves, it is therefore important that t-he intermediate wave frequencies be maintained constant and exact throughout the system. For this purpose, a part of every program should be sent out from station A or at certain xed times, a tuning wave of master frequency should be sent out throughout the entire system from station A, preferably earrying a definite audio signal to identify it. Such transmission of standard tuning frequencies is already practiced in respect of pure radio waves, by the Bureau of Stand- IUC ards at VVasllington, D. C., and it has been proposed by the commercial companies also to transmit standard frequency radio Waves from a master station to subsidiary stations, in order that distribution of frequencies may be accomplished by means of harmonics taken therefrom. I do not know however of any use of an intermediate frequency master 4 wave distributed over a system, particularly a mixed system of wire and radio links, for tuning purposes. I believe therefore that this is original with me and shall claim the same accordingly. Further than this, inasmuch as modulation of intermediate frequencies may take place at the B stations or even at the C stations by the use of modulator 64 in Fig. 4 or the circuit of Fig. 10, and as there Will .be many of these stations throughout the system, with a corresponding possibility of error, it is to be particularly understood that I contemplate the use of the long or intermediate frequency master wave sent out from station A for the purpose of calibration or tuning to resonance therewith of all the long Wave oscillator circuits 159, 160 and 161 of Fig. 10, or their equivalents." As a matter of fact, the tuned filter coupler 161 will be calibrated by means of this master wave. A convenient method of doing this is to receive the short Wave carrying the master long Wave on the antenna of a double demodulating receiver test set and the long wave from the oscillator 158 adjusted 1n frequency by tuning its circuit to give maximum sharpness in the receiver of the test set. Thus the circuits shown in Fig. 10 can be used for calibration throughout the system with a master tuning Wave sent either over the Wired trunks or by pure radio through the ether. In either case the pitch or frequency of the long wave transmitted will be identically the same; and its distribution over the system may follow the same channels as any other broadcasting, viz: by pure radio from A to B, relayed A from B to C, and again relayed from C to D to Atest out the subscribers circuits. Any dissonance detected in the last link between C and D, would be reported at once, as Suthciently serious to rece-ive immediate attention, because all tuning for intermediate fre- %uency or long Waves should be definit-e and Xed in the receivers, and therefore any variations must be taken care of at the sending stations. This has nothing to do 'with the antenna. I consider this method of calibrating and tuning` a system to be original with me and shall claim the same accord ingly.

As an alternative method, I may permanently impose the master long wave at superaudio frequency on all the relay stations through the trunks, to excite oscillator or more correctly amplifier tubes so as to produce intermediate frequency or long Waves,

Which may then be modulated, an'lplified` and transmitted in the manner shown herein or any other desired or suitable manner. To accomplish this, the only change in the circuit of Fig. 10 would be to disconnect the grid circuit from the plate circuitof the long Wave oscillator 158, and connect said grid circuit through a suitable tuned filter coupler to the trunks carrying the master Wave. The tube 158 will then be controlled as to its frequency of oscillation by the master Wave. In this Way a master frequency sent out through the system by either long Waves over the trunks, ordouble modulated short Waves through the ether, can be used permanently to excite and regulate every long Wave transmitter or generator in the system. As described, the B stations would relay the master Wave on a short Wave carrier to the C stations, maintaining this service constant While the program was in force, but if the master long wave be transmitted over wire trunks, then of course to that eX- tent the Wire trunks would be in permanent use for radio. This mode of actuating transmitter generators in synchronism by a distributed master Wave applies not only to the circuit of Fig. 10 but to any and all of the oscillators disclosed in the system, the frequency of the master Wave being determined according to the desired frequencies of oscillation in the transmitting tubes. I consider this method and type of apparatus for practicing it to be original with me and shall claim the same accordingly.

Coming to the subscriberis station, the primary Wave frequency which he recelves is fixed, but referring to Fig. 5a it will be observed that the filter coupler 33 shown between his first detector 3() and second detector 31 is provided with variable. tuning elements, as are also his antennna circuit 28 and his local input circuit 43. The subscriber may therefore select intermediate frequencies by merely tuning his filter circuit 33. In tuning, both sides must match up as Well understood by those skilled in the art. Thus, initial distribution by station A on several frequencies simultaneously results in selection at station B and relayin of the selected items, plus addition of original items, on several frequencies, all of which afford station C the opportunity of selection plus the addition of original matters, for relaying and transmitting to the subscribers D; while the subscribers in turn by tuning their intermediate Wave filter circuits can select any and all of the items desired and reject the others. It is of course possible for all the modulated frequencies at A to be relayed from B to C and from C to the subscribers, using Whatever number of primary frequencies and intermediate frequencies are available. This might actually occur when a national program lul) was being carried on which must be condensed in point of time, requiring the transmission of several items at once, from which the ultimate subscriber must 'select those which he would prefer to hear. I consider this arrangement and the method of operating relay stations in an organized system for purposes of selection of program to be new and original with me and shall claim the same accordingly. This applies as well to subscribers stations as to the intermediate and A stations, and to the entire system as such.

It is of course understood that any or all of the details, construction and operation thus outlined, may be changed and modified as necessity, convenience, and the resources of the art from time to time may dictate or permit, without departing from the .scope and purview of my invention. I believe I have disclosed a complete and operative system for the purposes described, which is lit) novel in totality, as well as in its several divisions and parts, and that the methods employed throughout are novel, when considered in an organized system. I do not claim the specific circuits shown except as hereinbefore stated, but I do claim the system of the parts and the method of operating the same, as herein disclosed and I wish it distinctly understood that I contemplate all non-essential changes and modifications which may be made therein.

iVhile the master station has been described as being located near the geographical center of the system, it may be permanently or at times located in any division, for example, at New York in the eastern division, controlling other divisions by wire or by radio relaying repeated from division to division. The master station. wherever located, is for the time being the center of the system.

What I claim is:

1. The combination with a general organized wire distributing system having a plurality of subscribers stations, of a radlo broadcast transmitting station. a plurality of first and second order relay stations, means at the broadcast transmitting station for transmitting signals on a double modu'- lated wave, means at each said first relay station for receiving said double modulated wave and retransmitting the intermediate wave thereof on a second radio carrier wave, means at each second relay station for receiving said second carrier wave and retransmitting the sai-d intermediate wave borne thereby on a third radio carrier wave, and radio receiving means at the subscribers stations arranged to receive and double demodulate said third radio carrier wave, individual wire connections between said second relay stations and the subscribers stations served thereby, trunking connections between said first mentioned broadcast transmitting station and the said first order relay stations and trunking connections between said first order relay stations and said second order relay stations, whereby signals station to said subscribers stations each on fixed radio carrier wave frequencies allotted permanently to the receiving means of the station next below it.

3. In a syst-em of the class described, a plurality of broadcasting stations arranged in classes in order of transmission for re-y laying by stages, the stations at each stage being increased in number over those of the preceding stage, means for initially modulating a superaudio frequency carrier wave or carrier current, suitable for transmission over wired circuits, with means for modulating this long wave or intermediate frequency upon a short wave of high frequency suitable for radio transmission, means at each relay station in the system to demodulate the short waves and remodulate the intermediate frequency waves on a different short wave carrier, and subscribers receiving stations equipped with means for demodulating both the short carrier wave and the long intermediate wave, to take off the audio ,signals 4. In a system of the class described, a plurality of broadcasting stations arranged in classes in order of transmission for relaying by stages, the stations at each stage being increased in number over those of the preceding stage, means for initially modulating a superaudio frequency carrier wave or carrier current, suitable for transmission over wired circuits with means for modulating this long wave or intermediate fre quency upon a short wave of high frequency suitable for radio transmission, means at each relay station in the system to demodulate the short waves, and means to transmit said intermediate frequency waves thus taken off, in the form of amplified carrier current, over wires to other stations.

5. In a system of the class described, a plurality of broadcasting stations arranged in classes in order of transmission for relaying by stages, the stations at each stage being increased in number over those of the preceding stage, means for initially modulating a superaudio frequency carrier wave or carrier current, suitable for transmission over wired circuits, with means for niodulating this long wave of intermediate frequency upon a short wave of high frequency suitable for radio transmission, means at each relay station in the system to demodulate the short waves, and transmit said intermediate frequency modulated waves as amplified, carrier current over wires to other stations, together with means at such receiving stations to receive said modulated llong waves and to amplify and remodulate the same upon short carrier waves and retransmit them by pure radio.

6. In a combined radio and wire system, a plurality of transmitting and receiving stations having both radio and wire apparatus, and means to modulate long waves and to interchangeably transmit the same over said wires or as modulations on short carrier waves.

7. In a combined radio and wire system, a plurality of transmitting and receiving stations including local or regional broadcasting stations having both radio and wire apparatus, and means to modulate long wavesl and interchangeably transmit the same over said wires or as modulations on short carrier waves, together with subscribers stations equipped with receiving means and wire connections to the local or regional broadcasting stations.

8. In an organized wired signaling system having a pluralit of groups of substations, the substations o each group being connected by wire to a service station common to the group and provided with radio receiving means connected to the service station over said wire connection for supervision therefrom, and means for transmitting by double modulation a common signal modulated intermediate frequency wave modulated on ,different carrier waves over a common area.

9. A combined organized wire system and organized radio system comprising means for producing a signal modulated wave of intermediate frequency, interchangeable means for distributing said intermediate frequency wave by wire and as a modulation on a radio carrier wave to subscribers receiving stations, double demodulating radio receiving means at said receiving stations arranged to detect and demodulate said intermediate frequency wave, whereby only such persons as are provided with such double demodulating receiving sets may detect lui said intermediate frequency wave, and means for independently and at will, broadcasting the same signal carried by the intermediate frequency wave as single modulations on a radio carrier wave whereby the signal may be made available for receiving instruments outside the system.

10. The combination of an organized radio broadcasting system with an organized wire communication system comprising aI plurality of subscribers stations D grouped in local areas, a local distributing station C for each such area, district rela stations B related to groups of stations (il and a master station A related to all the stations B, radio broadcast transmission proceeding from the master station outward through the relay stations B to C, and by relay distributing from C to D, all of said stations being provided with modulating radio transmitters for broadcasting original matter, means in each local area for connecting the subscribers stations D to the local broadcasting station C through circuits of the wire system, wire trunk circuits connecting the distributing station C to the district stations B, and other wire trunk circuits connecting said district B to the master station A, with means at each station A, B and C to receive double modulated carrier waves, with relay transmitters at each of the stations B and C comprising means to demodulate the primary carrier wave received, means for amplifying the intermediate frequency modulation wave, and means for modulating the same upon another short primary carrier wave for transmission at a different frequency from that of the primary carrier wave received.

11. In an organized system of radio broadcast distribution, means for transmitting double modulated carrier waves to receiving stations in fixed tune, means for independently transmitting a master wave of exact intermediate frequency over the system, and means to synchronize the transmitted inter-l mediate frequency therewith.

12. In an organized system of radio broadcast distribution, a plurality of means for transmitting double modulated carrier waves to receiving stations in fixed tune, common means for independently transmitting a master wave of exact intermediate frequency over the system, and means to synchronize the transmitted intermediate frequency therewith.

In testimony whereof I hereunto aix my signature.

EDWARD E. CLEMENT.

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