US1577106A - Radio distributing system - Google Patents

Description

*HAUWMMWMWMMWJ y March 16 1926'. 1,577,106

E: E. CLEMENT liAb'Io DISTRIu-TING SYSTEM original Fileg Sept. 25, 192.4

Patented Mr.' 16, 1926.

UNITED vSTATES PATENT oFricE.

EDWARD E. CLEMENT, F WASHDVGTCN', DISTRICT 0F COLUMBIA,.ASSIGNOB-'TO EDWARD F. COLLADAY, OF WASHINGTON, DISTRICT 0l' CDLUMBIA.

nemo nisrniaurii srsrnn.

Application led September 25, 1924, Serial No. 739,832. Renewed February-11; 1926.

To all whom t may concern:

-Be it known'that I, EDWARD E. CLEMENT, acitizen of the United States, residin at Washington, iii the District of Colum ia, l have invented certain new and useful Improvenients in Radio Distributing Systems, of which the following is a speci cation, reference being had therein to the accompanying drawings.

My invention relates toradiophone exclian e systems andI has for its object to simp ify and improve methods of controlling the broadcast distribution of 1ntelligenoe. 15 Brieliy stated, the invention compilises a radio-wire system, in which two sets of waves are radiated at diiferent frequencies, preferably from the central statioii, and both sets are received at each subscribers station, and bv means cf a special mechanism, the combined or resultant potentials are impressed upon the subscribers circuit, whereby oscillations at a frequency equivalent to the beat or differential between the two primary frequencies, will, be produced in the subscribers line to central,` which is tuned to said beat frequency. The oscilla.- tions thus set up in this resonating circuit are of long wave length, preferably of the $0 order of 10,000 meters, which corresponds to a frequency of kilo cycles per second.` I do not restrict myself to this particular frequency of wave length, but in'the av- A erage local subscribers telephone circuit,-

I have found suchl wave lengths to be suitable. At the central station end of the line, n detctor, with or with'anipliliers, (both radio and audio), receives the radio oscillations, detectsand rectities the same, and

l returns' corresponding audio frequency waves over the line to the subscribers station, where they are rendered intelligible by suitable receiving apparatus, not responsive to the primary or beat waves.

I shall describe .and illustrate the wave transformation herein as being from primary to beat wave frequency, and 'then through a central oiiice detector to audio frequency, so that audio frequency waves will flow back through the subscribers line.Av

With this specific form of the invention, the subscriber needs no special receiving apparatus, and may even use his ordinary' telephone receiver for receiving the medidations bruglit in on the radio carrier waves. It is obvious however, that instead of using this very simple arrangement,l I may4 cause the beat waves produced at the substation to oscillate in the line, so as to affect and be amplified by a radio amplifier tube or tubes, that is to say, in one or mre stages, 'at the central station, and sent back over the line thus amplified, to be picked -up by the subscriber, anddetected, rectified.and rendered audible at his station in the usual 66 way. 1 Certain advantages inhere in this ar rangement at the central oiiice. One is in respect to the simplicity of line connections, since all radio transmission is through'the 70 ether, and the only terminal attachmentsnecessary are multipled taps across the lines, each containin the tuning elements, andone coil. of a coup er.A Aftbo'thendsA of the line, these are the only'elements that need physi- 76 cal attachment thereto, and the tuning is such that audio frequency'telephone cur\ rents or battery currents-'are entirely unaffected thereby. Another advanta. e vat the central otlice is the concentration o detector tubes and circuits at central with the battery'l l supply and where constant inspection and care are rendered easy and simple, 4 This system isintended to be used for" distant receiving and distribution or for- 85' local-broadcasting. For distant receivin the central oiiice apparatus includes'a tuned receiving antenna circuit and a relay trans-1 mitter, which sends out the saine radio waves amplified; also a local heterodyning trans 90 nutter with a properly tuned aerial.' The modulations inthis case are carried on the relayed waves, and the local heterodyne waves may be unmodulated. Where local. s -broadcastiiiv is desired however, Iafsecond 5 modulated local oscillator circuit pi'o-v vided, which takes the place of the rela transmitter for distantwaves. -Thirs wit two local oscillators, it follows that. eithertrain of waves or both may be modulated 10 and this affords means to ive' out localgffv programs limited tothe su scribersonl without interfering with individual sul?)7 scribers reception of distant stations-when practiced with independent apparatus. l0' My invention is lillustrated in the accom# panying drawings, in wliic Fig. 1 is adiagram showing a, coinpletef;i Y

equipment for practicing the invention, with vacuum tube detectors used at both the subscribers and central stations.

Fig. 2 is a similar diagram of a fragment of the subscribers circuit showing a crystal detector used in lace of the vacuum tube.

Referring to ig. 1, at the central station are indicated a radio receiving and relaying apparatus RRand local oscillator LO.

The radio relaying apparatus RR has tuned antenna circuits 1 and 1, the local oscillator has a tuned antenna circuit 2. The radio relay may send out its local reinforced waves on a separate aerial, or on the un- ]5 tenne 1 or the antenna 2, as found expedient in practice. It is quite obvious that interference between these trains of waves can produce no ill e'ect, since they are intended to heterodyne at the subscribers station and 0 in the aubscribers wired line circuit. At the subscribers station 3 is one antenna circuit `tuned to the frequency'transmitted by the radio relay RR, and 4 is a similar antenna circuit tuned to the frequency of the cenu tral oiee local oscillator LO. AIf it be desired to avoid tuning entirely at the subscribers station, it may be done in the following manner: provide the radio relay set RR with either audio or rad'o means (such as a rimary heterodyne circuit) to change the re uency of the modulated waves received rom distant stations over the antenna 1, so that they will always go out locally on a constant wave length. In such case, the local oscillator LO would also be tuned for a constant wave length, and it necessarily follows that the tuning of the subscribers antennae 3 and 4 may then be for constant wave lengths as well as that of any local resonating circuit connected therewith. y

At the subscribers station I have shown the usual telephone set TS and a jack J bridged across the lim` to receive a plug P constituting the terminal of a local receiving circuit RC containing the telephone receiver TC and talking condenser AC, the

urpose of this being to prevent closing the line for battery current while listening to the relayed and amplified audio frequency currents coming from central.

At the central station J-,J represent the ordinary standard switchboard terminals of any desired type, to which the line 5-6 is connected for telephone communication with the suhscribers station SS. The' dotted lines in the middle of the figure represent that portion of the line which extends .between the subscribers station and the 'central olice. Across the ends I'brid e tuning elements I--Il and VC-VC, and cou ler coils C* and C. The line circuit is tun by means of these devices, and is maintained in oscillation durin receiving. a

At the subscr rs station the detector tube D has its rid circuit 8 coupled through the coils'C an C to the antenna circuits; and its plate circuit 9 coupled to the line through the coils C2. The input circuit 8 of the tube may be tuned by means of bridged condenser VGZ, to the mean frequency of the waves received from the two antenna circuits 3 and 4, and the output circuit 9 including one side of the coupler C is tuned by means of the condenser VC* to the beat frequency, the other side of the coupler C2 being similarly tuned by condenser VC. As usual in hetcrodyning vcircuits, the couiler C2 acts as a tuned filter to pass only the beat or long waves to line. The

central office coupler Ca has its secondary coil connected to the grid circuit of a detector tubel', whoseplate circuit 7 is connected to the primary of an audio frequency transformer AT, the secondary of which is bridged across the line wires 5 6. The long or beat waves sont over the line from the subscribers station ure thus demodulated and audio frequent-v waves are fed back over the line to the subscribers station, where they become intelligible in the receiving instrument TC or its equivalent. It is obvious that any desired number of stages of super-audio frcquenc amplification, or audio frequency ampli lcation may be inserted before and after the detector tube 7'. This use however of an amplifier per line or a plurality of amplifiers per line in a system for distributing broadcast matter, is not claimed herein, being described' and claimed in m co nding application Serial No. 89,410, fi ed ebruary 19, 1926.

Fig. 2 shows a form of crystal detector circuit which may be used at the subscribers sation instead of the vacuum tube detector circuit of Fig. 1. In vthis case the cou lers C- to tie 'mean of the received frequenciesand to their beat frequency respectively. I

What I cla'im is:

1. In a radiophone exchange system, u. central station and subscribers stations and wired line circuits interconnecting them, means to transmit modulated waves at radio frequency, means at the central station to transmit waves at heterodvning frequenciesv therefor, means at the subscribers stations for receiving both frequencies, means caus-l ing them by heterodynmg to reduce in the su scribcrs line circuit a beat requenc and means in said circuit'at the centrale ation for detecting and rendering intelligible .to

the subscriber the modulations carried upon original carrier waves, and transferred therefrom to the beat waves.

2. In a radiophone exchange system, a.

central station and subscribers* stations with wired line circuits intcroonncctin them, means for transmitting modulat radio waves over the area containing the subscriband Cz are tuned as before lll 1 also at the centra ers stations, means at the central station for relaying andlamiliying said' wavesz means station for producmg and radiating waves at heterodyne frequencies,

means at a subscribers station for receiving ers stations, means at the central station for relaying and amplifying said waves, means also at the central station for producing and radiating Waves at heterodyne' frequencies, means at the subscribers stations for receiving both the original and heterodyning waves, means including a detector for impressing the oscillating potentials of said waves upon the subscribers line circuits so as to roduce' modulated beat frequency waves t erein, detector means for said beat waves connected .with a ,subscribers line at the central station, and means at the sub'- scribcrs station responsive to ,saidy :nodu- In testimony whereof I hereunto'aix my signature. l

EDWARD E. CLEMENT.

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