US1805446A - Radio broadcasting system - Google Patents

Description

RADIO BROADCASTING SYSTEI Original Filed 00%. 6, 1923 4 Sheds-Sheet 1 L/G/II' J.-

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E. E. CLEMENT 111mm BROADCASTING SYSTEM Original Filed 001:. 6, 1923 a, Z 2 508665,? rat/wave u: EXCl/lA/Gi 200 aecnclc 4/01/7- saw-x44. 07-4770 4 Sheets-Sheet 2 May 12, 1931. E. E. CLEMENT 1,305,446

mum; BROADCASTING sYsi'nu v Original Filed Oct. 6, 1923 4 Sheets-Sheet 3 I U J? L j'lllllllll 3 J IN T L ewe m arc/M70121: (ASTIMW 657' Emmima May 12, 1931. E. E. CLEMENT 1,305,445

RADIO BROADCASTING SYSTBI Original Filed Oct. 6, 1923 4 Sheets-Sheet 4 Patented May 12, 1931 UNITED; STATES PATENT OFFICE EDWARD E. CLEMENT, OF WASHINGTON, DISTRICT OF COLUMBIA, ASSIGNOR TO EDWARD F. COLLAJJAY, OF WASHINGTON, DISTRICT OF COLUMBIA RADIO BROADCASTING SYSTEM 4 Original application filed October 6, 1923, Serial No. 667,024. Patent No. 1,576,309, dated March 9, 1926. Divided and this applicat on filed March 8, 1926. Serial No. 93,325.

My invention relates to broadcasting systems. The present application is a division of my prior application, Serial No. 667,024, filed October 6, 1923, and patented under date 5 of March 9, 1926, as No. 1,576,309. For a completely organized system of this kind there are a number of essentials to be considered which have not yet been rendered available in pure radio transmission to my knowledge. Among these are, secrecy or restriction of the service to those alone who pay for it; uniformity and continuity of service equal at least to those possible in standard wired system; efiiciency in transmission and fidelity in reproduction; testing, control, metering and supervision of the service from a central point. It will be observed that these requisites of good service call for means of both distributive and selective character, that is to say, means for distributin the broadcast program or communications to all consumers in common, and means for individualizing each consumer for any purpose when necessary. It is the object of my invention to supply these means by superposing an organized broadcasting system upon a combination of existing wired systems, and without interfering with the ordinary functions of said wired systems, to

. utilize their characteristic forms and arrangement for the appropriate guidance, dis

tribution and control of modulated high frequency or carrier current waves as well as direct and alternating current supply, and

the like. Such wired systems are already divided by the nature of their respective services into two general classes, distributive systems, including electric light, power and telegraph circuits and some many-party telephone circuits; and selective systems, including telephone exchange systems and all others that have individual wires leading to the subscribers or consumers.

I attain my object by combining in use these two classes of systems, connecting transmitting and receiving stations to both, i. e.,

to the electric light or equivalent network on one side and to the telephone line wires on I the other. By this means all the receiving stations or subscribers stations are accessible in common for broadcasting over the common or distributive medium, and each station is also accessible individually over the telephone circuit allotted to it, or to which it is allotted. In building up a complete system so as to organize on an interstate or national scale, this arrangement contemplates regional distribution, i. e. distribution in territorial districts local in character, such as a city or a county, and relaying from the national or international sending stations through the regional or district centers to the local subscribers. The general broadcasting may be by any known or suitable means either wire or radio or combinations of wire and radio transmission, which I shall claim herein.

My invention is illustrated as to one form in the accompanying drawings, in which:

Fig. 1 is a schematic diagram indicating the layout of a general system having high power primary broadcasting stations and relayed local or regional distribution;

F i9. 1a is a similar diagram showing wire distribution from a primary station to local or regional distributing stations.

Figs. 2 and 2a taken together show some detail of the circuits and connections in the local or regional distribution area, also a metallic circuit metering scheme.

Referring to Fig. 1, 1, 2 and 3 represent telephone subscribers stations, connected by wires 4, 5 and 6 to the central telephone exchange C, and all assumed to be supplied with electric light current over a common wire network indicated at 200, from a central station 7. superposed upon these two wire systems is a broadcast distribution system having a central station R fully equipped with switchboards and a line radio or Squier transmitter for broadcasting over the wire network 200, with which it is connected as indicated at 208. This station R is also equipped with receiving and relaying apparatus for diiferent wave lengths, and has access to all lines in the telephone system through the exchange C, as indicated by trunk wires 15. Associated with the telephone subscribers stations 1, 2 and 3, are broadcast receivers 1a, 2a and 3a, each physically connected on one side by wires 10, 20, or 30 to the electric light circuit 200, and on the other side by wires 11), 2?) or 3?; to an individual telephone line 4, 5 or 6.

In operation, messages or programs broadcasted by means of wave radiation from primary stations as 12, 13 and 14 are received at the regional central station R and relayed through the Squier transmitter by means of guided waves or modulated carrier current over the network 200 to all the local stations at 1a, 2a and 3a in common, the service being supervised, controlled and metered over the individual telephone lines as 4, 5 and 6. Instruments 1a, 2a and 3a are standardized and adjusted to one wave length, so that little or no local tuning is required, all tuning being done at the central station It, the operator there being able to listen in on the local subscribers receiving instruments over the telephone wires, and to determine thereby the correct adjustment of transmitted wave length.

In addition to relaying messages received by radio waves from primary stations, the central station R is equipped with local modulating and Squier transmitting apparatus, for originating programs and distributing the same over the network 200; and in this connection there are provided trunk or long distance telephone wire connections for bringing in news, communications or programs from distant points by wire and relaying them out over the local area through the Squier transmitter. I lay no claim to the use of long distance telephone wires per se, but consider the use of the same in combination with the network 200 and the local individual telephone wires as 4, 5 and 6, to be within the scope of my invention, as creating an alternatiie all wire system which can be depended upon for maintaining continuity of important service when static or other conditions make the receipt of radiated waves from primary stations uncertain, and I shall claim the same accordingly.

Such a combined system, or all wire system, is shown schematically in Fig. 1a wherein R indicates a central station similar in all respects to the station E of Fig. 1. except that in addition to being equipped with radio receiving and relaying apparatus it is also equipped with apparatus arranged to receive broadcast matter transmitted from a primary station 12 over a wire line or trunk and to relay the same through a line radio or Squier transmitter over the wire network 200 with which it is connected as indicated at 208.

Other central stations R, R and R are furnished with broadcast matter from the primary district station 12 over wired line or trunk circuits. each of which other local distributing stations, R, R and R serve a itretwpzrk 200 similar to that served by the staion In this modification of the invention, the operation is the same as that of Fig. 1 except that programs received at the several regional central stations from the primary station 12 are received over wire lines. Any of the regional stations may also receive by radio from the primary station 12 or other primary stations thus giving flexibiliay to the system and greater assurance of uninterrupted service.

Referring to Figs. 2 and 2a, I have therein shown circuits of the central ofiice and substation equipments and connections, Fig. 2 representing the telephone side of the system, and Fig. 2a the broadcasting 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 office circuits clear of all grounds or other disturbing connections during conversation. When the broadcast receiver goes into service, by closing the filament switch its operation in receiving is identical with that of any similar receiver. Each set is provided with a cut off relay energized when the telephone set goes into commission, either by calling or being called, and at the central office whenever the broadcast operator takes control of the line, he disables it in the usual manner by pulling up the cut 011' 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 now that the line is held on the broadcast board, and subject to interruption for telephone connection. I prefer to use this tone test only with the broadcast operators testin g plug, because his regular connecting plug includes within its functions that of connecting a subscriber through the station amplifier to the broadcasting transmitting set, and a connection of this character should not be interrupted without permission.

Referring particularly to the diagram, Fig. 2, A and A are two subscribers stations connected by line wires 1617 and 18-19, respectively, to the central station C where they terminate on jacks J and J. PP are plugs forming the terminals of a cord circuit 2021, 22-23, having a bridged repeating coil 1*, ringing and listening keys is and k, supervisory signals ss' and bridging connection to the main battery B. The same battery is shown supplying current to the line relays L, L, and through contacts of the cut oit relays L L 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. The circuit of the line relay, for example, relay L, may be traced from battery B through the left hand winding of L, left hand contact of L sleeve line 19, wires l9c19d, through L (Fig. 2a), subscribers telephone set, line 18, right hand contact of relay L right hand winding of L back to rounded side of battery B. Battery supp y for the connected lines is thereafter taken through the cord circuit 2022, 21-23, in a manner well understood in the art. When the substation 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. 2a, it will be observed that the broadcast switchboard which I have designated generally by the letter R, is connected to the subscribers lines by multiple taps marked 16a, 17a, and 17 Z), and 18a, 19a, 19?). These terminate on multiple jacks J J corresponding to the multiple jacks on the telephone switchboard. It should be noted that throughout this system the tip wires 16 and 18 with their branches are the grounded wires of the system, while the sleeve wires 17 and 19 and their branches, are connected to battery. This is extended into the broadcast 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 off from the telephone terminals to the broadcast receiver terminals as indicated at 180, 190, and 19d. (The receiver is shown only at one substation for sake of simplicity of illustration). The two branches 190 and 19d are taken from the sleeve or battery side of the line 19, and are connected to opposite terminals of the winding of a relay L, which constitutes the substation cut off relay for the broadcast receiver. The winding of this rela is bridged by a condenser 9 through w ich both ringing and voice currents can pass without substantial impedance. Where the broadcast receiver is attached to a party line substation, this relay L may be omitted, since on such party lines there are usually grounds on one side or the other.

Normally that is to say when the telephone circuit is not in use the cut ofi relay L is deenergized and as a consequence the wire 190 is connected through a back contact of the relay L through extension wire 24 to the branch 25 connected to the A battery marked A in Fig. 2a. The wire 18c similarly passes through a back contact of the relay to the extension wire 26 leading to test or listening relay L and ground. 18cv it will be remembered leads to the tip or ground side of the line, therefore it is the side which in the broadcasting can be made use of with a permanent ground or grounds without disturbing the balance of the telephone circuit.

The broadcast receiver at the substation A is shown as comprising an input connection 28 (from the electric light network 200), a tuned coupler 29, detector tube 30, audio amplifier tubes 31 and 32, and the usual transformers 33, 34, 35, the last mentioned transmitting the amplified audio waves to the telephone receiver or loud speaker 36. The filament battery is A The plate battery is B and suitable tuning condensers and coils, tickler coil for regenerative effects, etc., are provided as required. I should remark in passing that this representation of the radio receiver is intended to be typical only. The present invention does not concern itself specifically with the design of the local broadcast receiver sets, and other circuits and apparatus may be substituted for those shown in the diagrams without departure from the invention.

The relay L has four pairs of contacts, one pair 27 a closing the wires 25 and 37 from battery A to the filaments. The second pair 27 b closes the wires 25 and 38 so as to put battery A on the transmitter T, and through the induction coil winding to ground. The third and fourth pairs of contacts 27 0, 27d, close the wires 39 and 40, forming terminals of the secondary induction coil winding 1, to the tip and sleeve side of the telephone line respectively, through the back contacts of relay L. The transmitter T is shown hanging upon a hook switch H controlling the connection of wires 41 and 42, constituting a parallel link between the battery A and the filament bus 43. Thus the filament can be heated and the broadcast receiver put in service either through the agency of the relay L or by the switch hook H. The former is controlled by the broadcast 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 I of the induction coil I, and I interpose a pair of condensers g, 9 between the secondary I of the induction coil and the telephone receiver 25 on the one hand, and the terminals of relay L on the other, so that while the subscriber by means of switch it can connect his telphone T-t' for receiving calls over the telephone line, he cannot originate calls thereover from the broadcast receiver extension.

Returning now to the central station, and particularly to the broadcast department thereof shown in Fig. 2a, T represents a Squier broadcasting transmitter, symbolized in a very simple form, but supposed to contain the usual elements and connected on the output side with the electric light or power network 200. This connection includes suitable devices, known in the art, to exclude high voltage and low frequency currents, surges, hum, etc. Suitable switches are assumed located ata convenient point. The jack J connected to the amplifier t 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 connectin any of the wire lines to said transmitter. Letailed appliances for receiving radio messages from primary centers, for the switching, and for the local broadcast transmission, are well known in the art, and need no specific description in this specification.

The cord circuit between plugs P and P in Fig. 2a is the same as the operators cord circuit in Fig. 2, but the broadcast operator also has special test cords such as that shown in the upper part of the figure connected to plug P. Here the keys KK' are of standard construction, as in the other cords, and the test contact of the plug P is connected through suitable resistance to the supervisory lamp 8 to the broadcast battery B, means such as the commutator p being provided to give special tone test on the test thimbles of the multiple jacks J, J, J 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 A, produces charging of that battery by the constant flow of current therethrough from the main radio battery B at the central ofiice. This charging circuit may be traced from battery B through contact of relay L", wire 19a, 19, 19c, contact of relay L, 24, A, and through natural ground back to battery B. The amount of energy thus delivered to the battery A depends upon the size of the line wires, and the len 'th of time available for such charging. As shown, the batter wire 24 is not cut ofi except when the cut 0 relay L pulls n which is only when the line wire is in use or conversation. With No. 19 line wires, and usin only the sleeve wire for conduction, it wou d be possible to safely transmit from one-half amere to two or three amperes, according to the ine resistance and the voltage of the batter emplo ed. Where this voltage is standar manua telephone voltage, say 22, and the single wire resistance to the substation is from 25 to ohms, it would be possible to maintain the battery A continuously charged, provided the time of discharge be not too long extended, and the charging be not interrupted by other contingencies, such as the excessive telephone use of the line.

I wish to point out in connection with this, that the art has progressed to a point where filament current required is so small that it is well within the limits of the amperage permissible over the smallest telephone wires, even continuously flowing, and therefore direct feed of the filaments over the telephone wires is not only possible but, for reasons that will be plain to those skilled in the art, will be the best practice. It is also possible with instruments now well known to supply filament current from electric lighting circuits, as shown for example in Letters Patent to Lowell No. 1,455,141, May 15, 1923, and both these methods of feed are within the sea e of the present invention, owing to my com ination of these wires into one system.

For metering the subscribers radio service at the central station, an impulse meter which may be of the standard type as indicated diagrammatically at 50 (Fig. 2) or any known or other suitable type capable of recording current impulses or circuit closures is employed. This meter is arranged to have its energizing circuit closed through a normally open contact 51 of a relay 52 actuated conjointly with the line lamp, which in the present case is the usual night alarm relay. For actuating the meter 50 from the subscribers broadcast receiving station at substantially constant time intervals, a meter actuator in the form of an intermittent circuit closer of any known or other suitable type is provided. In the present arrangement this actuator 53 is shown as an intermittent thermal switch of the type used as sign flashers. The energizing circuit of the actuator 53 including the winding 54 and contact 55 is connected with the electric light circuit 200 through a normally open contact 56 on the broadcast receiving station switch hook H, while the circuit closing contact 57 is connected in shunt of the subscribers telephone-transmitter circuit-switch-hook-contacts, so that upon closure they will effect a closure of the line circuit in t e same manner as when the subscribers telephone receiver is raised except that the closure is momentary or brief and not continuous.

Thus when the radio receiver is in use the switchhook H being in raised position maintains the contacts 56 closed which maintain closure of the energizing circuit of the actuator 53 which circuit may be traced from the lower conductor of the power circuit through conductor 58, winding 54, contact 55, conductor 59, contact 56, conductor 60 back to the upper conductor of the power circuit. This causes the actuator 53 to warp back and forth and intermittently open and close its own circuit in a manner well understood, which causes the contact 57 to be intermittently actuated to momentarily close the line circuit at the subscribers end over the following path: contact 57, conductor 61, switch-hook contact a, line wire 18, line wire 19, switchhook h, conductor 62, back to contact 57. Each momentary closure of the subscribers line circuit efi'ects an actuation of the line relay L in the usual manner as when calling, except that the actuation is momentary, which in turn efl'ects an actuation of the meter manna:

50 throu h relay 52 and its contact 51. The circuit 0 relay 52 may be traced from battery B, through winding of relay 52, line lamp and contact of line relay L back to the grounded side of battery B. The circuit of meter 50 may be traced from the free or upper side of battery B through contact 51 of relay 52, winding 50a of meter 50 and back by way of ground to the grounded side of battery B. The meter 50 as shown is a standard \Vestern Electric line meter of a type in common use.

It has a high resistance winding 50a and a low resistance winding 50?), which causes it to operate as follows: When circuit is first closed through the high winding 50a, the

' meter 50 is energized quickly to pull up its armature and close the circuit of the low resistance or working winding 50?). A rush of current flows through this low winding, which then actually turns the ratchet wheel of the meter. This could be replaced by any suitable electrically actuated counting device which would respond to closure of its circiut at the contact 51 of relay 52. Thus, as long as the broadcast receiving station is in use, the meter 50 is actuated at substantially constant recurring periods proportionate in number to the time the receiving station is in use. It is to be noted that while the meter 50 will be actuated once each time the subscriber closes his line circuit in initiating a telephone call, and that it will not continue to record the time of use of the radio receiver during use of the telephone substation, there will however be no unfairness in the broadcast service charge due to the fact that, in practice, the suspension of metering during use of the telephone substation will substantially compensate for the extra actuation of the meter at the initiation of a call.

As stated above, an intermittent circuit closer of any suitable type may be used in place of the meter actuator 53, for example, any kind of an electrically operated motor of fairly constant speed may be used to effect the momentary closure of the telephone line circuit.

A number of modifications in the arrangement of the electric light and telephone wires in the system thus specifically described can be made without departure from the scope of the invention.

Such modifications need not interfere with the ordinary electric energy feed (battery) over ordinary telephone circuits as usual, but on the contrary permit full use to be made of the following combination, which I believe to be novel: (1) energy feed over ordinary telephone circuits as usual, (2) transmission of filtered wave bands over the telephone circuits, (3) return of wave bands over other telephone circuits. The supply of current energy to the subscribers stations permits 10- cal supply of carrier current component at the subscribers instruments with a minimum of complication.

Summing up, and particularly to make clear terms that will be employed in the claims appended hereto, the following definitions are given: The local area is that containing a group of subscribers such as 1a, 2a and 3a in Figs. 1 and 1a. A central station or a regional central station is that which serves the local area and the subscribers mentioned, therein, such as R in Figs. 1 and 1a. A primary station is one such as 12 supplying programs or signals which are to be received and distributed by the station It among its subscribers in the local or regional area. A district station is one such as 12d in Fig. 1a, which serves a number of central stations such as R, R, R R as indicated in Fig. 1a, the said central stations then distributing the program or signals received from district station 1211!, each in its own local or regional area and to its own subscribers. A district station such as 12d may receive programs by radio or wire from primary stations, such as Iii-14 and may then distribute the same among the central stations in its district, which in turn will distribute them each to its own local subscriber in its own regional or local area. In any case, the primary station is that which originates a program or signals, and in this sense the district station 120? may also be a primary station for all matters whichit origlnates.

lVhat I claim is:

1. In a broadcasting system, the combination of a central broadcasting station serving a local or regional area, subscribers stations in said area, a common power wire net work connecting said central station and said subscribers stations, a primary transmitting station, means for transmitting broadcast matter from said primary station to said central station and means at said central station arranged to relay said broadcast matter over said net work to its local subscribers as modulated carrier current, together with means at each subscribers station to receive and demodulate said carrier current, and other means actuated in the operation of said receiving means for signaling between the subscribers station and the central station.

2. In a broadcast distributing system, a district primary station, a regional central station, subscribers stations grouped in the local area around said central station, a common power network in said local area connected with said central station and said subscribers stations, means for transmitting broadcast matter from the district station over an individual wire circuit to said central station and means at said central station for retransmitting the same therefrom to the subscribers stations over said common wire network, together with means at each subscribers station to receive and demodulate said carrier current, and other means actuated in the operation of said receiving means for signaling between the subscribers station and the central station.

3. In a broadcast distributing system, a primary or district station, a plurality of central or regional distributing stations, a plurality of subscribers stations grouped around each central station, a common power wire network connecting each central station and its local group of subscribers stations, individual wire line circuits connecting the primary or district station with said central stations, means at the primary station for transmitting a broadcast program Over said individual wire line circuits to the different central stations and means at each central station for receiving and relaying the said program broadcast to the subscribers in its local area over its associated network, together with means at each subscribers station to receive and demodulate said carrier current, and other means actuated in the operation of said receiving means for signaling between the subscribers station and the central station.

4. In a broadcast distributing system, a primary or district station, a plurality of central stations, a plurality of subscribers stations grouped in the local area around each central station, means including trunk wires for directly transmitting broadcast matter from the district station to each of the central stations and means including a power wire network for transmitting broadcast matter from each central station to its group of subscribers stations in common, together with means at each subscribers station to receive and demodulate said carrier current, and other means actuated in the operation of said receiving means for signaling between the subscribers station and the central station.

5. In a broadcast distributing system, a district primary station, a regional central station, subscribers station grouped around said central station, means for transmitting matter to be broadcasted over an individual line circuit to the central station, a common wire network connecting the subscribers stations and the central station, means at the central station for relaying the matter received thereat over said common network, in-

dividual wire lines connecting each subscribers station with the central station, and metering means at the central station controlled over said individual wire lines from the different stations.

6. In a system of broadcast distribution, a central broadcast station and subscribers stations served therefrom, wired power distributing network and a wired telephone exchange system, a broadcast receiving set at each subscribers station, means for transmitting broadcast from the central to the subscribers stations over said network, and centralized metering means controlled individually from the subscribers stations over the wires of the telephone exchange system responsive to the operation of the said subscribers receiving sets.

7 In a system of broadcast distribution, a central station, subscribers stations, a network connecting said stations in common, means at the central station for supplying power to said network, means for transmitting broadcast matter over said network to said subscribers stations, broadcast receiving means and thermionic tubes therefor at the subscribers stations, means for supplying energy to said tubes derived from said network, a telephone exchange system having individual line wires interconnecting said subscribers stations, and means at the subscribers stations for connecting and disconnecting the energy supply means from the network controlled over said individual lines from a central point.

8. In a system of broadcast distribution, a central broadcast station in a local area and subscribers stations served therefrom, a local wired power distributing network and a local wired telephone exchange system, a broadcast receiving set at each subscribers station, means for transmitting broadcast matter from said central station to the subscribers stations over said network, and centralized broadcast metering means controlled individually from the subscribers stations in the operation of the said subscribers broadcast receiving sets.

9. In a system of broadcast distribution, subscribers stations in a local area, local means for supplying power current to said stations, a common wire network connecting said power supply with said subscribers stations, means at a central point on said network for receiving modulated waves at radio frequencies, means for reducing said frequencies to carrier current frequencies suitable for transmission over the wire network, receiving instruments at the subscribers stations having tunable input circuits connected to said network, and output circuits with audio receiving means connected thereto, together with means actuated in the use of said receiving instruments to signal said central point.

10. In a broadcasting system, the combination of a central broadcasting station, subscribers stations grouped in an area around the same, a common wire network connecting said central station and said subscribers stations, means for furnishing power to said subscribers stations over said network, a wired radio transmitting apparatus connected to said network at a central point, radio receiving instruments connected to said network at the subscribers stations, a flasher at a subscribers station, means actuated in the operation of the radio receivin set at said station to communicate current mm the power circuit to said flasher, and means controlled in the operation of said flasher to transmit signaling current to said central point.

11. In a broadcast distributing system, a district station adapted to receive modulated waves at radio frequencies, a plurality of central or regional distributing stations, wired connections between said district station and said regional stations, a plurality of subscribers stations grouped around each regional station, a common wire network connecting each re ional station and its local group of subscri ers stations, means in each local or regional area to supply power current over said local network to the subscribers stations, means at the district station for changing the frequencies received to carrier current frequencies suitable for transmis sion over the wires, means for transmitting said modulated carrier current to the regional stations over the connecting wires, means at each regional station for amplifying and transmitting said modulated carrier currents over its local power network, and means at each subscribers station for receiving and demodulating said carrier currents.

In testimony whereof I hereunto afiix my signature.

EDWARD E. CLEMENT.

CANADIAN l-TEIITE LOWELL ET AL ESPENSCHIED AFFEL BR. PAT.

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