US1700580A - Radio frequency communication system - Google Patents

Description

Jan. 29, 19.

L. BE'GIN RADIOFREQUENCY COMMUNICATION SYSTEM -2 Sheets-Sheet Filed March 1926 avwemtoz LU CIEN BEGlN g l qhisr aflomm 'ai g I Jan. 29; 1929. I 1,700,580

L. BEGIN RADIOFREQUENCY COMMUNICATION SYSTEM Filed March 1926 2 Sheets-Sheet 2 22 \l qr 11k 4,

Him I mmma gvwemtoz LU CHEN BEGN 1" "W I a UM Patented Jan. 29, 1929 I UNITED STATES.

- 1,700,580 PATENT OFFICE.

LUCIEN BEGIN, or rears, raANonnssIeNon or ONE-HALF 'ro WILLIAM B. WEAVER, or BIRMINGHAM, ALABAMA, AND HAROLD r, WILHELM, on NEW YORK, N. Y.

:aAnIornnoUENoY oommu'NIcA'rIoN SYSTEM.

Application filed March 2, 1928, Serial No. 91,669, and in France March 13,1925.

particular, insignalling networks comprisin a plurality of correspondents making use 0 'but a limited number of signalling frequencies.

It is known that there exist duplex signalling networks comprising a plurality of correspondents which, just as in shipboard and coastal stations, make-use of but one and the same stand-by wave-length and in which the calls are discriminated by the manual or {5 automatic transmission of a given number of wave trains for each station, these impulses being selectively translated at the called station either into a single signal by means of mechanical selector mechanism or by the I mere acoustic identification of a predetermined series of impulses. On the other hand, it

it is possible to establish a two-way communication between two stations such as M, N,

2 providing'reception at each station be made to take place at a wave frlaquenc sufficiently different from that used therein or transmission, which amounts 'to. say that station M -mus t transmit waves of say frequency f and receive on frequenc f WhllShStltlOIl N must do the opposite. hen it is desired to extend this classical method of duplex signalling to f f a network comprising a plurality of correspondents such as M, N, O, P, it is obvious is also known that two other correspondents without the. latter perceiving his interfering carrier-wave.

In accordance with one application of the present invention, the possibility of such disturbing carrier wave transmission by third parties is eliminated while yet allowing the third party to listen in.- This is accom' lished by first selectively calling-the desire party only and then by locking the 'transmittin equipment of all the other. stations comprised in the network. With this object in view, a

given party shall be called by transmitting waves of the same frequency as that to which the stand-byapparatus of all the stations is tuned, and then by modulating those waves at a relativelylow frequency, --disti nct for each statiomaswell as by designing the'if stand-by equipment of each station such as wave frequencies 'for' duplex communication between any two stations, Fig. 2 illustrates another mode of carrying out the invention by the use of electron dis- I charge tubes.

Referring now to 1, in this'figure the terminals of the apparatus, leading to either munication or to the line conductorsin the case of wired commumcation, are denoted the serial system in the case of wireless comby 60. Those terminals lead, on the other hand, to two coupling systems 48-- 50 51 -53 and 48-50-51-52 one of which is provided to transmit efiiciently a given, frequency, such as f, to the exclusion of all other frequencies'and particularly of frequency f whilst the other system is provided Q P to. do the opposite. Assume the arrangement designated by48-'50-51- 53 is provided to efiicientlytransmit f and the arrangementdes'ignated by 48-50-51-52 is provided to transmit f. In that case, trans- 5 that the operation, at any given moment,

. must be restricted to the communication be-' I ,t'ween anytwo stations with the momentary exclu'sion of all the other stations, just as in party lines comprising several subscribers 5 sets. In the latter case, however, it is usually;

" possible for any subscriber whatever, other v than the two already communicating, to he ten in towhat is going on over the line without the knowledge of the two active corre 45 'spondents. In carrier wave duplex signaL, ling, however, the apparatus is usually so designed that it'suflic'es to liftthe receiver of thehookfso that the transmitting gear be automatically thrown into operat ve condi- 5 .tion and the carrier wave itself emitted even if. the operator does not modulate its ampliq tude by speaking in front of the microphone. It is obvious that,-under such conditions, it I is hardly possible for a third party. to listen as in to the communication taking place between former-48 should not permit the .transmission of f and, reciprocally, it should not be j possible to transmit frequency f through transformer 48. With that object in view,

one of 'thewindings of 48=shall be shunted by a parallel circuit- 5O tuned to f and having a-high C/L ratio so as to offer. but negligible *reactance for short-circuiting all fr other then f and then there shall be inserted waves of frequency), i. e., all frequencies excepting 'f will be highly shunted by the trap circuit 51 and then frequency f in particular will be highly impeded by the series rejector 50 tuned to that frequency. By means of the relays 54, 55, each acting as a double pole double-throw switch, it will be possible to assign either of these coupling vunits to the detector 56 and the other to the transmitter 31, or conversely.

During the stand-by period, the output of detector 56 is connected to the exciting winding of a relay 40 through the primary of transformer 14 having a trap circuit 13 across its terminals and serially through the back contacts of three other relays 41, 47

and 43. Relay 40 is shunted by a condenser cuit of battery 22 through contacts 59 and the Winding of a drop relay 20, the latter being shunted by a condenser 19 which by passes the undulatory component of the current. The parallel circuit 13 is tuned to the each station, and its object is to provide a shunt of negligible reactance to all modulation frequencies other than that intended to' operate the fork relay 57 of the called station.

Terminals 33 of the transmitter 31 are intended to be connected to the modulating system, that is, to the keying arrangement in the case of telegraphic signalling and to the microphone system in the case of telephonic signalling, and, during the calling period only, to a source of definite low frequency,

distinct for each station to be called.

In the drawing the telephone transmitter 24 may be connected. thru transformer 25 and filter 26 to the. back contacts of relay 30.

'The front contacts of relay 30 may be conne'cted selectively to either source of low frequency 28 or 29 depending on the position of key 27 Relay 30 may e operatedby.

depressing key 37. The low or modulating frequency source 28 or 29 may be' connected according to which station it is desired to call. The armatures of relay-30 may be connected to terminals 33 of the transmitter 31 to. modulate the high frequency output of current.

While transformer 14 at each station will be designed so as to efliciently transform only waves of the frequency of fork 57 to which it is connected, and which corresponds to the modulation frequency for calling that station, it will be advisable, however, to avoid the fork relays of the uncalled stations being put into operation b successive transient resonance effects resu ting from those components df speech modulation as may coincide with the natural time period of'the various forks. With that end in view, forks having natural time periods as widely separated as possible from the focus of the speech frequency s ectrum shall be chosen and then a suitable lter circuit 26 shall be used to sup-- press right at their origin, i.e., in the microphone system, such components of the speech transmitter 31 with the desired modulating as coincide with the modulation frequencies frequencies exclusively so as not to distort the speech by excessive curtailment of those components which determine its intelligibility.

Let us now consider a few possible conditions of operation of the system, when the detector 56 1s connected say to the coupling arrangement for f, as illustrated. (a)-One of' the distant stations of the network transmits an unmodulated carrier wave of frequency f, which may be the standby frequency. Under those conditions there will appear at terminals 60 from the distant station a corresponding alternating E. M. F.,

which will be transmitted'to the input ter-- minals of 56 through the selective couplernatural-time period of the fork relay 57 at- 4850-5l* 53 which, will give rise, in

the output circuit of 56, to a direct current of constant mean value. This constantcurrent will operate the relay 40 through'the primary system of 14 and the back contacts of relays 41, 47 and 43. It is obvious that this direct current flowing the primary system of 14 will be without effect on its-secondary. The v closing of bu'sy'relay 40 will, on one hand operate the busy signal 38 and, on the other.

hand, will-prevent all possible operation of transmitter starting relay 41 through the receiver being eventually lifted off the hook 42.

(b)-One of the stations transmits a carrier-wave of frequency f also but modulated at a frequency other than that of the fork 57 at the station considered. The effect of this transmission on the standby apparatus of the receiver in question will obviously be the 6 in to a conversation offering eneral interest in the operation of the networ A monitoring relay 47, operated by a push-button 46 on the desk set, has therefore been provided in I orderto enable him to connect his receiver 11 with the output of detector 56 through trans-.

former 12, by substituting"- the primary of the latter for the stand-by relay 40, transformer 14" and trap 13, by means of one of the make contacts of relay 47 without,-however, un-

15 looking his transmittervstarting equipment.

(0)- One of the stations transmits a carrier wave of frequency f modulated at the natural frequency of trap circuit 13 and hence at that of fork 57. Under those conditions,

there will be'obtained, at the output of detector 56, a unidirectional current the mean amplitude of which will vary at the frequency of trap circuit 13. The latter will then behave as a very high impedance for the low frequency component and will hence give rise to a large potential drop across its terminals. The primary winding of 14 will therefore be subjected to an alternating E. M. F. corresponding to that of the modulation of the calling carrier wave.- This E. M. F. will be transferred across the secondary which will in turn operate the winding 58 setting 57 into vibration. I 1

As stated above, the vibration of fork 57 will cause the operation of the droprelay 20.

The drop will in turn operate the ringing relay 43, the operation of which will, on one 'hand result in the closing of the circuit of bell 45 and call 1amp44, and, on the other I 40 hand connect the telephone transformer 12 to the output of detector 56 in place and instead I of 14 and 40. The switching out of the latter will prevent sustained operation of the .busylamp 38 and locking of starting relay 5 41. The operator at thecalled station considered may therefore lift the receiver oif 42 a and thereby close the starting relay 41 which I will in turn make a contact at the starting terminals 34 of the transmitter through one Q of the back contacts of monitoring relay 47 and battery 22, on one hand, and, on the other hand willcause the bell to cease operating by opening its circuit. I

It will be understood that by placing battery 22 on the starting terminals 34, the trans-' mitter 31 whichmay be an electron-discharge tube will be started. If there be any modujlating potential at the terminals 33, the high frequency current generated by the transmitter will be modulated thereby.

The communication will thus be established between the called station and the stat on having transmitted the call. On replacing the receiver at 42 at the end of the communication, call lamp 44 and bell 45 will give the which would correspond to a call initiated by ometer slider and the ositive terminal of hatthrough signal informing the operator that he must lift the drop of relay 20 and thereby restore the stand-by connections. I It will be noted that the exciting windings of shift-over relays 54, 55, are connected in parallel with startin terminals..34'of the transmitter 31 throug one of the back contacts'of ringing relay 43. They will therefore be operated simultaneously with the starting equipment branched at 34 providing, however, that ringing relay 43 has not been operated just previously to the receiver be- I ing'lifted oil the hook. Incase ringing relay 43 would not have operated previously,

the local station, the shift-over relays 54, 55, would then be operated simultaneously with the starting equi ment connected at 34 and transmission Wou d then take place" on frequency f whilst receiving would automatically be carried out on frequency f. I It will be. understood that transmitter 31 gen erates both frequencies f and f frequency v f being transmitted and f being suppressed, if the arrangement 485051 53 'be' con- 9 nected to the transmitter; and frequency f being transmitted. and f being suppressed, if the arrangement 485051'-52 be connected to the transmitter. There will'thus be realized a duplex signalling system in which transmission will automatically take place on f and reception on f if it is-the station considered which initiates a call, but in which the opposite will automatically occur if the station'set's his apparatus into operation as a result of a received call. Referring now to Fig. 2, there is shown a diagrammatic representation of another mode of carrying out the invention which comprises the use'of a three-electrode tube detector for rectifyin the carrier wave in place and instead of t e schematic detector 56 of Figure -1' and also of a second threeelectrodetube 16 for rectifying the low-fie quenc alternating component of the calling modu ation. Tubes 3 and 16 have their filaments heated by the common source 7 through steadying or ballast resistors 5 and 18, voltmeters 4 and 17 being branched across their respective filament terminals in order to through the carrier-wave input circuit 1-2 and the in ut circuit14-15 of the low-frequency ca ling device. Potentiometer '9 is branched across a battery 6 intended to suitably bias the grids with negative potential. I Capacity 10, branched across the potenti tery'. 6 operates in y-passin oscillations around the potentiometer resistance, The output circuits of both tubes are also fed off I a common source 8. I The output circuit of tube 3 is connected to the various elements ofthereceivingapparatus in a manner simi larto that of. the detector 56 of Figure 1.

One oft-he mainadvantages of the diagram. of Figure 2. is that it enables the use ofliiglier'modulation frequencies for effectwhich are useful in maintaining the natural characteristics ofthe speaker. On the other hand, inthose stations provided with but low' transmitting power. and making use of high- 1y resonant circuits, care will have to be exercised not to modulate .the callingpcarrier wave at an excessive frequency for it can be shown that. the same would involve a decrease in transmission. efliciency resulting fromthe virtualuntuning of the circuits due to modulation. 'In fact, a carrier wave of frequency f modulated at a lower frequency F gives rise to waves of: frequencies fl-F", f and f -l-F It willthus be seen that a ortion of' the total power of the unmoduated wave will appear in the form of waves of di erent' frequencies which, in view of the highly resonantcircuitsused, will not befiansmitted as efficiently as'the wave f itse In thisfigure there is. shown a push-button 37 used ior. the operation of relay 30 through battery 22.. The operation of this relay re-- sults in the substitution, during the calling period, of one of the low-frequency sources 28, 29, to the microphonesystem 2425-26, normally branched. across modulation terminals 33 of'the transmitter 31. F

In the case of a network wherein communications between various stations are not very frequent, it will be possibleto effect an economy by switching. the second tube 16 out of circuit during the stand-byperiod providing,

1 howeventhat it be automatically re-insertedinthe circuit as soon as. a. call is despatched by any other station ofthe network. Figure 2 shows a diagrammatical form of realizing this disposition. It will suffice to open the switch 23 normally closing the filament circuit-oftube 16* and then to utilize, in parallel with 23, one of the make contacts of relay 40in order'to restore theclosing of same followingthe arrival ofany carrier-Wave.

The output terminals 32 of thetransmitter are' branched to an output coupler-36-35E which may lead to an antenna, a loop, or a line circuit in accordance with known methods.

The low-frequency sources 28, 29, for mod ulating the calling carrier wave may be. constituted. by ordinary'microphone hummers or w tuningiorkoscillators operating in front of the. microphone, providing the filter 26 be simultaneously put out of circuit, or else by utilizing one of: the. amplifying or modulatingtubes as alow frequency osclllator during the calling period. In the. latter case, it will be. preferable to make. use ofcircuits compris ing no magnetic coredinductancesin. order to avoid that: the fundamentalifrequencies thereby obtained for calling modulation be not accompanied by harmonics which might. op-

erate. the fork relays of other stations. than the one called by a given, fundamental.

It: goes without saying that the-vibrating Y relay has. been represented schematically by a tuning fork relay 57 and that, in accordance with the invention, thesame' maybe replaced by any equivalent vibrating relay, suchv as vibrating reed relays etc. This remark also holds good as regards. the other switching relays represented onl in their schematic form. In particular, the rop relay 20 may be replaced by a polar relay the armature. of which will be deviated in one direction by the volt- .age appearing across the b -passing condenser 19 and thereby establish contact 21, and which will be deviated in theo posite ii-- rection by an opposite voltage res ting from the through signal and therebyrestore the stand-by connections. In a siimlair manner, the coupling units 48 -50--51'-53 and 4850--51-52 of Figure 1 may be replaced by the elementary couplers of Figure2. Different batteries 22 have been shown in order to simplify the diagram of connections, but it must be understood that thesebatteries may merge into a single commonbattery' in accordance with well-known. common battery practice. Lastl it will be possible to insert amplifiers fore. andfollowin either for both tubesv 3 and 16 aswell; as be ore and following the schematic detector 56.

Having thus described the invention, I claim:

-' 1-. In a. high frequency communicationsys stations each having a transmitter and a receiver, means whereby any station may directly selectively 0811 5 desired Station only 1 5' and means whereby the transmitters of the undesiredstations are locked when said desired station is called.

3'. Ina high frequency communicationsys I tem, a plurality ofsignalling stations each I havmg a transmitter and a receiver, each station having a common stand-by high'frequency and a distinctive stand-by frequency, means whereby the transmitter of any station may send out the stand-by high frequency and the distinctive stand-by frequency.

of the desired station, the stand-by high frequency locking the transmitters of the undeslred stations and the distinctive stand-by frequency causing a signal at the desired station.

4. In a communication system, a transmitter, a receiver, a coupling-unit passing only a given first frequency, a second coupling unit passing only a given second frequency, shift-over relays, a signalling device, starting equipment for said transmitter, said re lays normally and simultaneously connecting the first coupling unit to said transmitter and the second coupling unit to said receiver, and means whereby said starting equipment may start said transmitter and shiftsaid relays to interchange the connections of said coupling units with said transmitter and receiver if said signalling device has not been operated just previously to said starting equipment and yet only start said transmitter if said signalling device has been operated just previousiy1 to said starting equipment.

a communication system, a transmitter, a receiver, a coupling unit passing only a given first frequency, a second coupling unit passing only a given second frequency, and means for simu taneously assigning any one of said coupling units to said transmitter and the other of said coupling units to said receiver, selectively,

6. In 9. hi h frequency communication sys tem, asi'gna ing station comprising, distinctive signalling apparatus responsive to a distinctive signal, a busy relay, a receiver, a receiver hook, a detector, a transmitter, a

" ringing relay responsive to o eration of said apparatus to give signal an to de-energize said busy relay, a transmitter starting relay under series control of said hook and said busy relay, said transmitter starting relay 7 being operated by said hook to place said receiver in communication with the detector tem, a signallin station comprising a receiver, atransmitter, distinctive signalling apparatus responsive to a distinctive signal, a. busy relay, a transmitter starting relay, a receiver hook, a detector having one output terminal connected thru said apparatus and busy relay to a back contact of said transmitter starting relay, said terminal also being connected thru said receiver to the forward contact of said transmitter starting relay, the armature of said busy relay being in series with said hook and said transmitter starting relay, the other output terminal of said detector being connected to the armature of said transmitter starting relay.

8. In a high frequency communication system, an electron discharge tube detector having a trap circuit tuned to a distinctive fre-- quency and a busy relay in its anode circuit, a rectifier circuit connected across said trap circuit and comprising a second electron dis charge tube, the cathode heating circuit of said second tube having in its path an armature of said busy relay, said armature being normally open, said busy relay causing said second tube to function and operating a busy signal when a stand-by frequency isimpressed on said detector.

9. In a high frequency communication system, a detector having an output circuit which includes a trap circuit, a rectifier circuit connected across said trap circuit and including an electron discharge tube, and means in said outputcircuit for controlling the cathode heating current of said tube.

10. A high frequency communicating system comprising at least two stations each having a transmitter and a receiver, said stations having a common stand-by frequency, said having means for receiving said fr uencies only means whereby any station, if initiating a ca must transmit on the stand-by frequency only and receive on the second freqency only, and, if receiving a call, must recome on thestand-by frequency only and transmit on the second frequency only.

' ".LUQIEN BEGIN.

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