US2287044A

US2287044A - Radio relaying system

Info

Publication number: US2287044A
Application number: US335217A
Authority: US
Inventors: Fred H Kroger
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1940-05-15
Filing date: 1940-05-15
Publication date: 1942-06-23
Anticipated expiration: 1959-06-23

Description

June 23, 1942- F. H..KRoGER RADIO REL'AYING SYSTEM Filed May 15, '1940 5 Sheets-Sheet 1 ifm.

INVENTOR FRED h'. KROGER ATTORNEY June 23, '1942- F. H. KROGER- RADIOZRELAYING SYSTEM Filed May l5, 1940 5 Sheets-Sheet 2 m as@ S MH .w

' ATTORNEY June 23, 1942. KRGER RADIO lRELAYING SYSTEM 5 sheets-sheet 4 Filed May 15, 1940 WOS QWM.

FRED //FOGER ATTORNEY June 23, 1942 F. H. KROGER RADIO RELAYING SYSTEM 5 Sheets-SheerI 5 Filed May 15, 1940 RJ Eg l m INVENTOR FRED H. K ROGER MM ATTORNEY Patented June 23, 1942 f RADIO RELAYING SYSTEM Fred H. Kroger, Patchogue, N. Y., assignor to Radio Corporation of America, a corporation of Delaware Application May 15, 1940, Serial No. 335,217

(Cl. Z50-15) 20 Claims.

IThe present invention .relates generally to a radio relaying system employing a plurality of repeater or relaying stations, and relates specically to methods of and means for efficiently relaying signals at ultra short wavelengths, and also to circuit arrangements for indicating at a central or division office the operating conditions existing at any one or more stations of the relaying system.

The invention nds particular application to a radio relaying system wherein there is employed at each repeater station an emergency power supply system with vmeans for automatically switching the station apparatus from the Ypublic power supply to the emergency power supply in the event of failure in the public power supply system. Correspondingly,'the restoration of normal voltage to the public service power supply causes the station apparatus to be switched back from the emergency power to the public service power. In such a relaying system it has also been suggested that two sets of amplifier equipment be provided with means for automatically switching both the receiving and transmitting antennae from one set to the other in case of a drop in or failure of output for the transmitting antenna. For a more detailed description of a relaying system employing automatic switching or change-over apparatus of the type described above, reference is herein made to my United States Patent, No. 2,017,126, granted October 15, 1935.

An object of the present invention is to provide a circuit arrangement for ruse with a relaying system of the type described above for indicating to a central oilice or division center which power supply system and/or which amplier equipment is in use at a particular relay station. The terms division center or central cnice herein designate a maintenance center to which is assigned the responsibility of maintaining in working order a certain number of repeater stations in the relay system, these stations constituting a zone. Where numerous repeater or relay stations are employed, there may be several such zones.

A further object is to conveniently and effectively control signal transmitting apparatus at a radio repeater station from a remote point with a predetermined signal to which only the controlled station is responsive.

Another object is to provide a radio repeater station in a relaying system with means which is selectively responsive to a predetermined signal transmitted fromthe central oce or division center for sending to the central office a signal characteristic ci a particular circuit condition at said repeater station. For achieving this purpose, there is provided at the repeater station a circuit which automatically transmits a plurality o f code signals indicative of vparticular circuit conditions then vexisting at that station.

A further object is to provide av radio relaying system especially adapted for the transmission of frequency modulated signals.

The present invention provides a system whereby the status of the individual relay stations can be communicated to the division center at the will of that center, in a way that requires only one communication channel which can also be used yfor other communication purposes.

A feature of the invention is a special circuit `arrangement at each repeater station including on to the next repeater station, a transmitter and associated transmitting antenna, two sets of amplifier apparatus (one automatically efi fective in case the other fails), an emergency power supply automatically effective in case the public service power supply fails, a selector or iilter associated with the receiver and responsive to a characteristic signal for driving a motor, a plurality of rotatable code discs driven by the motor, a pair of Vcontacts associated with each code disc, a relay connected in common to all contacts and responsive to the movements of said contacts for causing signals characteristic of r the code discs to be sent out by said transmitter,

and relay means associated with the amplifier and power supply equipment for rendering effective only those contacts and code wheels which correspond to the code designation of the `particular equipment being used.

In the accompanying drawings, Figs, la and 1b taken together illustrate diagrammatically a complete radio relaying system many of whose features have been designed by me and successfully tried out in practice and to which the principles of the present invention may be applied; Fig'. 2 illustrates schematically apparatus at one repeater station of the relaying system for achieving status indication in accordance with one embodiment of the invention; and Figs. 3 and 3a taken together show apparatus embodying the principles of Fig. 2 as applied to a repeater station, and also apparatus for performing additional functions.

'Ihe radio relaying system shown in Figs. 1 and la is designed for use particularly with television signals, although it will be vunderstood that it may also be used to transmit telegraph signals or any type of radio signal. The system includes a transmitting station A, a plurality of intermediate repeater stations B and C, and a receiving station D suitably spaced apart along the line of transmission. Repeater stations B and C are designed to repeat the signals from station A to station D. The arrows indicate the directions of the signals between the respective stations. Although only two repeater stations have been shown, it should be understood that this number is illustrative of any number of repeater stations which may be located at frequent intervals along the line of transmission for amplifying and reradiating the signals.

The antenna system indicated at the transmitting station A is shown to be of the omnidirectional broadcasting type, having constant characteristics over a frequency band sufficiently wide to accommodate the full band spectrum of high definition television. This antenna consists of two separate, independent radiator systems I and 2, the former for sound and the latter for vision transmission, both radiators being supported on a common column located at an appreciable distance above ground, usually on the top of a tall building. The antenna system of the transmitting station A is of the type installed on top of `the Empire State building in New York city, New York, and is described quite adequateing and reradiating the signals to the next repeater or receiving station along the line of transmission Since the transmission range of the ultra short waves at which this system is designed to function depends upon the air line or visual distance, a factor proportional to the height above the earths surface, it is proposed to locate all stations at points having as great height as possible, such as mountains, tall buildings, radio masts, etc. The receiving antenna 3 at repeater station B consists of a pair of dipole arrays placed one behind the other and suitably phased relative to each other for providing a .unidirectional effect. This antenna is designed to receive the signals transmitted from station A. Reference is hereby made to Carter United States Patent No. 2,183,784, granted December 19, 1939, for a suitable description of antenna 3. The reradiating or transmitting antenna 4 of station B is of the metal parabolic type which has as its focus a plurality of folded dipole antennas arranged in the same straight line. The folded dipole antenna has been found to be much more effective than the single `dipole and is of a general form described in copending application Serial No. 155,385, led July 24, 1937, by Philip S. Carter. At repeater station C there are shown a receiving antenna 5 and a reradiating or transmitting antenna 6, both of the parabolic type employing folded dipole antennas, as described in connection with antenna 4 of station B. Antennas 5 and 6 are, of course, effective in different directions, the receiving antenna 5 being positioned to receive the signals from station B while the transmitting antenna 6 is positioned to transmit the signals in the direction of the next adjacent station D. Antennas 5 and 6, as well as all the equipment at station C, are enclosed within a thin wooden cylindrical container 'I mounted on a steel tower. Aside from the metal bolts and screws employed in the construction of the wooden cylinder, there is no extra electrically conductive material employed, mainly because I have found that the presence of metallic strips or bands for the wooden cylinder causes a distortion in the `directivity pattern of the antennas and undesirable feed-back therebetween, and also causes a loss in signal strength. The wooden enclosure functions not only to mount the equipment and the antennas, but also prevents disturbances caused by wind pressures, sleet, ice and dirt from interfering with the normal characteristics of the antenna system and the associated apparatus. The commodious interior of the Wooden container also simplifies the maintenance of the equipment and enables suitable heating apparatus or other desired equipment to be provided within the enclosures.

The antenna 8 at receiving station D comprises a parabolic reflector having at its focus a plurality of folded up dipoles, this antenna being of course directed to receiving the signals from antenna 6 of the adjacent repeater station. The antennas of stations A to D, inclusive, have been described as being of a particular type, mainly by way of example, since it is apparent that other types of antennas can be used to achieve the desired results.

In the operation of the system of Figs. la and lb, television signals emanating from broadcasting station A are amplitude modulated and radiated at a frequency of 45.25 megacycles and received on antenna 3 at station B from which the signals pass to a 72 ohm coaxial cable 9 to a television receiver I0 to provide a Video component the band width of which is 4 to 6 megacycles. This video output is used to control a transmitter with multi stages of frequency tripling. In order to convert the signal into centimeter waves, the video component, through the intermediary of frequency modulator II, modulates a variable oscillator I2, the output of which is at the mean frequency of 52.6 megacycles with a variation of plus or minus .33 megacycle. This output is passed on to a frequency tripler stage I3 which provides an output of 158 megacycles with a variationof plus and minus 1 megacycle or higher, this last output of 158 megacycles being passed on to a final tripler stage I4 from which there is obtained an output of 474 megacycles with a .band frequency deviation of plus and minus 3 to 6 megacycles, and higher, if desired, which last output is passed on by a '72 ohm coaxial cable 40 to the transmitting antenna 4. It will thus be seen that the amplitude modulated waves of 45.25 megacycles received from transmitting station A have been converted into frequency modulated waves of a much higher frequency, of an order near 500 megacycles. The vacuum tubes employed in the tripler process, as well as in the final stage in a straight amplifier 'B to fsend .out test signals comprising a single picture'havingxaband width of from zero to 5 megacycles. There ris Valso vprovided a switch I1 which,. depending .upon 'the position in .which it is thrown, enables the :attendant at Ythe repeater station `B to observe onra kinescope I8 and an 'oscilloscopell the-output radiated over antenna 4 or the input received for the television receiver 1d. For this vpurpose there is provided a monitorconverter which converts the frequency modulation .from the final'stage of the tripler `Mito suitable video signal waves-which can be observed. Thefkinescope I8 provides the picture signal :while the oscilloscope I9 shows the wave form of the signal.

Atrrepeater station C'the receiving antenna 5 receives the 474 nzegacycle `frequency modulated signal radiated by antenna 4 Vof station B and covnertsthe signal by meansofa converter 2! to a 100 m'egacycle signal ifor more eflicient amplification. This `liOU vmegacycle signal is ampliiied by :a three stageamplier 22 and then con verted in 123to an output frequency modulated signal having a mean frequency of 4M megacycles, which is then transmitted `by antenna -5 toward the next adjacent station, in this case receiver'station D. Oscillators 2d -and'25, associated respectively with converters 2l and 23, function at 374 and 364 ymegaoycles respectively to change the incomingr frequency down from 474. megacycles to 100 megacycles `and then to kincrease the frequency ofthe 100 megacycle component to 464 megacycles. Here again an amplieris provided betweenthe converterzland the `transmitting.antennai, and a monitor converter 26 is utilizedto provide video signals io the local kinescopeland oscilloscope 28. It should beobserved'at this time that intermediate station C Aconverts the frequency modulated -waves received on one frequency .into frequency modulated Waves of another frequency whichare then reradiated.

At :the final receivingstation D in the relay link, the frequency modulated 'signal is received on antennafa at Ai6/i megacycles 'and converted by apparatus '29 to a 100 megacvclesignal which is then .passed on to an amplifier and limiter 3!! to a second `converter-3| which reduces the sign nal to 29 megacycles before it is passed on to detector 32 which transforms lthe frequency modulated signals to amplitude -modulauted signals. The output of detector 32 comprises video signals which are amplified by amplifier 33 so that they Vcan be suitably observed by the local kinescope .34 and thevlocal oscilloscope 35. Oscillators 36 and 31, associated respectively with the con verters v29 and 3l, generate 364 megacycles and 129 megacycles respectively to reduce the signalsto'the frequency values mentioned above. If desired, the output fromfamplifier having a four-megacycle'band width-and higher can loe passed by .means of :cablei to a vsuitable estudio lfor."-'rebroadcasting over .a .second lloroadcasting .transmitter (not'rshown'k In the :radiolrelay embodiment l'shown in Figs. la `and 5111i, and .successfully tried :out-in; practice,

.the transmitting .antenna .A was located i on :top

of the' Empire vState .buildingin .New York,A New York; :the repeater station B was located .at Hauppauge, Long Is1an'd,'New York, vabout 45 milesavvayirom the EmpireState Building; the repeater station C was located at ARocky iPoint, Long Island, New Yorkywhich is about :fteen ymiles from Hauppauge; and :the receiving station D was located :at Riverhead, ,Long'Island,

'New York, a distance of fifteen milesfrom -station C. These-distances between the stationsy are .notto be `considered .asbeing limitative incharacter, since the stations'tmaybe separatedffrom one :another any desired-distance, so longas any two adjacent stations .sare within .the optical range of visible distance. `This is because the electromagnetic Waves `at the lower .wavelengths below ten meters, let lus say, with which therelay system of Figs. :1a fand lb are :particularly concerned, have characteristicsl which are fquasioptical in nature; that is, they have aivery delinite limited range -oftransmissionrwhich is cornparable with the optical range.

Fig. 2 illustrates diagrammaticallya repeater station .equipped with apparatus .in accordance with the invention forautomatically. sending to a division center or central oiiicezaplurality of signals vfor indicating the operating conditions existing at the repeater. Inthis figure the receiver and transmitter.arediagrammatically indicated inbox form and appropriately labeled as such, and their respective associated-antennas 40 and 4| are also diagrammatically indicated, although it will be understood that the antennas .as well ras ythe Vreceiving and transmitting Aapparatuscan be of any suitablekin'd such as, for example, those shown in repeater stationsB and C of Figs. la and 1b.

At each repeater station, as lshown in`Fig. i2,

there is provided Va selector mechanism 43 responsive toa characteristic signal for operatinga relay whosecontacts control a motor'M. On vlthe shaft of the motor`M there are provided four code ldiscsrr', b', lc' and `d which are provided with segments according to a prearranged code. `The segments `of each code disc or wheel occupies less than"1180. The segments on disc a' Vare on the opposite 180 side from code disc c', .and correspondingly the segments for code discs lb and d' are opposite to each other although respectively on the same`180 as a `and c', .as shown. This arrangement permits two code'i'signals to be transmitted when the motor operates, the possible combinations of-which are a .and c', .a and-d', b and c', and b and d'. 'Associated with 'each code disc or wheel are a pair of contacts `45 which normally are open but are arranged to close when contacted by a raisedsegment on therdisc. lOne Contact of each disczor zwheel .is connected to the correspondinglypositioned contact of .each of the other pairs, and 'these correspondingly located contacts in turn'connected to Aone terminal of the winding or a "relay '46,"the other terminal of which is connected to the positive side of a battery-or suitable ysource of unidirectional energy41. tacts'45, `4'5`is connected to acontact of one of the relays 48, "4Q-or50. jThus,:the opposed fcontacts Yof relays 48-andr`4`9 are connected' to dif- The other'contact of eachpair of conferent contacts of code discs a and b', while opposed contacts of relay 58 are connected to different contacts of code discs c and d', as shown. The armatures of relays 43, 49 and 58 are connected together and to the negative terminal of battery 4'|. A spring 5| associated with the armature of relay 50 normally pulls the armature 50 to the upper or break contact in the absence of energizing current through relay 58. The Winding of coil 50 is connected to the public service power supply or some apparatus associated therewith, so that when the apparatus at the repeater station is being energized from the public service power supply the relay 5U will be operated and the armature will be pulled down to engage the make contact. Relay 48 is connected with one set of amplifiers, while relay 49 is connected to the other set of amplifiers, so that depending upon which set of amplifiers is operated the relay 48 or 49 will be energized, thus pulling the armature either up or down, or if the relays are positioned horizontally, to the left or to the right. The armature of each of the relays 48 and 49 will remain in the position in which it is pulled until such time as it is pulled in the opposite direction by energy in one of the relay windings. It will be obvious, of course, that relays 48 and 49 may comprise a single relay of the polarized type having a pair of windings. It is assumed, of course, as mentioned above, that the relay station is provided both with an emergency or spare power supply so that when the public power supply fails the emergency or spare power supply immediately takes over the burden of supplying excitation energy to the receiving and transmitting apparatus at the repeater station, and correspondingly, that when public power service is restored the translating apparatus at the repeater station will automatically be switched or changed back from the emergency to the public service power supply. It is also assumed that one set of amplifiers automatically replaces the other in the event of failure of one of these sets. The failure of one set of ampliers may manifest itself when the radio output of the relay station is reduced to a value which causes the system to cease to function. This value need not be absolute radiation failure. When this occurs, there will be a shift from one amplifier set to the other. Operation of the relay station may be started and stopped by radio signals sent over the relay system. Obviously, the code disc wheels a', b', c' and d' can be replaced by commutator wheels, and the contacts 45 by brushes or suitable contacts engaging the commutator wheels. Thus, each commutator will have a predetermined number of contact segments separated byinsulating centers for sending out desired code signals, it being understood that when the motor is at rest the contacts or brushes will engage an insulating sector.

The operation of the system of Fig. 2 will now be described. Assuming that periodically, let us say, every hour or so the attendant at the division center desires information as to which pieces of apparatus are functioning at the different relay stations. To obtain this information the attendant at the maintenance center sends out a signal which is characteristic of a particular relay station from which information is desired, it being understood that each station has a characteristic signal different from the signals of the other stations. This signal may be a code signal or,

vvamargo-i4.

preferably, a tone of constant frequency .and amplitude. This transmitted tone sent vout,.by the maintenance center is received over antenna 40 and the associated receiver and passed on through line 52 to the transmitter and associated antenna 4| which transmits the signal on to the next station of the chain. A branch circuit 53 at each repeater station passes this tone to the selector 43 and if this selector is responsive to the tone sent out by the maintenance center it will cause the operation of relay 44 which, in turn, will close its contacts over an obvious circuit tc operate motor M and cause the rotation of four code wheels a', b', c' and d'. The motor is so arranged that it will rotate the code wheels only once and the code wheels will again come to rest in the position indicated in the drawings with the contacts open circuited, unless the tone signal from the division center is being continuously transmitted, in which case the motor will rotate for an integral number of revolutions during which the characteristic signal is being received and passed by the selector 43. As the motor and the wheels rotate, the contacts 45 close in accordance with the code characteristics on the discs to operate relay 46 which in turn closes its contacts 54 to affect the transmitter over leads 55 to cause this transmitter to send code signals to a division center. If desired. these code signals can be sent out continuously until stopped by the maintenance or division center. The code signals transmitted by the repeater station of Fig. 2 over antenna 4| may or may not be radiated in the direction from which signals are received over antenna 48, depending upon whether or not the transmitted code signals from the repeater station are received directly by the division center or through the intermediary of another division center. If the public service power supply is being used, the relay 58 will be operated and will pull its armature down against the restraining influence of the spring 5|, thus closing an obvious circuit through the winding of operating relay 46 and the segments of code wheel d' when the motor is operated. However, if the public service power has failed and the emergency power supply is being used, the armature of relay 50 will be in its normal position and will be contacting the upper contact, thus closing an obvious circuit for code disc c' to send outl a different code signal. In the same way, the two sets of amplifiers operate on the relays 48 and 49 to condition either code wheel a' or code wheel U to send out code signals via relay 46, it being understood, of course, that the codes are different for the various code wheels. Thus, during the operation of the motor M the code wheels will send out two consecutive signals, one indicating whether the public service power supply or the emergency power supply is functioning and the other indicating which of the two sets of amplifiers is being used. As soon as the attendant at the division center obtains this desired information, he will 'cease sending the characteristic tone signal, thus stopping the motor and restoring the shaft and code Wheels to their normal rest position. This cycle of operations will be repeated for all the repeater stations within the zone of the division center.

Figs. 3a and 3b considered together illustrate a preferred and practical circuit embodiment which can be installed at each of the repeater stations of the relaying system for indicating to the division center not only the status of the amplier and power supply equipment, but also for indicatingv the noiselevelj and carrier level, as well as anyother desired condition of operation; The system of Figs. 3a and` 3b also includes a'- start and stop arrangement for conditioning the repeater station tooperate or to shut down. In these last figures there are shown a public service power supply-outlet indicated diagrammaticallyY as 33; an. emergency or spare power supply system indicated by the rotary converter 30 and battery 3|; a pair ofamplirler systems each including a preamplifier 64 or 65 and a power'amplier 6,6 or 61; switch-over

devices

22 and 23 for associating the receiving and transmitting antennae with the particular preamplifierand power amplifier required for operation; time delay apparatus ||4 for isolating necessary automatic change-over at a particular station without interfering with the individual functioning of the other repeater stations; selector apparatus 6|, 62 and 63for`selecting and passing to the propernrelay the tone signals received over the service channel; code discs 66 for sending code signals indicative of the status of the various pieces of equipment atthe repeater stations; and various relays and switches associated with the foregoing pieces of equipment.

In the operation of the system of` Figs. Saand.

3b, assuming that it is desired to start up the repeater station at which this apparatus is located, the remote central oice or division center (not shown). will send out a tone A over. the

service circuit, which may be either a wire lineY or a radio channel. If a radio-channelY is used for the service circuit, then it is preferredthata narrow band of frequencies be used thereover which is outside the range of the message waves, and that separate amplifiers and repeating equipment (antennas, etc.) be used therefor at the repeating stations than for the message waves. This start tone A will start up all the relay stations in the system simultaneously and will be sent out for at least thirtyseconds. The start tone will be received at each repeatervstation and passed on to the selectonequipment where only selector 6| willv pass tone A1 through to a tone amplifier and rectifier 10the latter producing a rectified current for operating relay |02. The operation of relay |02` will close its contacts andcauseA the operation ofV relays ||0, |00, |04, |06V and |01. The path forv operating these relays will be traced over a circuit from the positive-terminalfof battery 3| through theoperating coilof" relay ||0, lead H5, contact of relay |02, lead H6, to one'terminal of the coils |06, |01, |00 and in parallel, through theseA coils to'lead H1, then tothe negative terminal of battery 3|.

When relay H0 operates, the closing of the left the plate and-filament supply leads 13, 'I4 and 15 and 16 for the preampliers and power amplifiers, respectively. It should be noted at this time that relay Voperates when the public service Voltage is above a minimum value determined by under-voltage relay 24, and it has been assumed that this relay! wasvoperated before the Voperation of; relay |.|0.V .Manually operated switches .22,.23,. I8;` I9 and20 and 2| determine which set;- ofi amplifier equipment andtheir respective power. supply outletis to be used inthe normal operation of the repeater system rand which isv to .function asiaspare. Assuming that switches 2,2, and23 arethrown upward, andithat relays, |00 and |0|, nowy operated; pull their respective. armatures to the 1eft,.it will be obvious that the .transmission line Y|23-from the directive receivingantenna; andthe transmission line |24 from thezdirective. transmitting. antenna; will. be connected: through the lefthand terminals O f the reversing switchesand the lefthandblades of switches 22.and. 23. to;one.set of. power amplifier;

equipment comprising preamplifier 64 and. its associated; power'. amplier 66;. Thisstate of facts .requiresth'at switches I8 and20 be thrown down and switches. |.9..and 2|. .thrown up, in. order to supply.` power to. theplatesand. filaments 13 and 15lof. the .preamplifier 64: and power amplifier 66, respectively., throughtheoperated contacts of. relays. .|661 and..|01. .Theradiation of carriercurrent .overtransmission line |24 will occur in;some. thirty. secondsafter the operation. of. relay |.|0. By. exposure to. this radiation through proper coupling of. transmissionlines. |25 and. |26, radio frequency currentswilli. be passed on. to. diode 18 and converterv and rectifier 19.. `The output of diode 18 will` pass` currentA over leads |28. and through rthe rwinding of relay |'.|3 .for enabling current toA be-.supplied to ,the .holding winding of relaysf |00; .-|.0|,. :|013 and. 0.6, the last. holding. winding,vnamely 10.6, .being operated by the .intermediate oraccessory. relay |05', in-the manner .now to bel described; .The outputof this. diode 18 passing current .over..leads |.2Blwill .operate relay H3; thusbreak-ingthe normally. made contacts leadingv from the -motor ofthe time delay. relay. |4to-its power Supply. At thisrtime itshouldbe observedA that--the time-.delay relay. I4.` hadv its operating circuit closed uponltiieA operation of relaylildithroug-h apathextending over leads |21 and thenormall make contacts o fv relay ||3, as-a consequence ofV which the-time.- delay relay ||4 (comprising some suitable motor arrangement such-asa telechron motor.,r here given by wayvr of example only) .will rotatethe commutator |2| clockwise` through the shaft'. shown, andV cause theY segmented cam -|.20to commence its trayel. Thecommutator |2|vwill-continue to rotateuntil the operating4A circuit fon the time delay circuit |'|v4 is opened at Ythefcontacts of relay H3. .The operation of relay ||3, which will occur approximately-thirty-seconds aftertheinitiation of.. the start signal',- will stop the rotation of the time delay motor maintaining contact V| |9 in about the mid positionY on onevof theelectrically conductcircuit until cam |20 reaches the beginning of segment-position #1', sayfor thirty seconds.

In the event that all repeater stations in the systemA which start` upsimultaneously function in intended manner. withA no failures in equipment, then. alloffltherepeater cams |20 at the variousstations will stop at the midposition of #l segment. The electrical circuit for the'rst relay station in the system will be constructed to open at the end of the #l segment position on the cam. The circuit for the second or next relay station will be constructed to open at the end of the #3 segment position on its particular cam. The circuit for the third repeater station will be constructed to open at the end of the #5 segment position on its particular cam, while the circuit for the fourth repeater station will open at the end of #9 sgment position, etc.

In the event that the amplier selected by operation of relays and I0| fails after having started to function, there will then be insufficient radiation over output transmission line |24, and insunicient output from diode 18 to maintain relay ||3 operated. The restoration of relay |I3 to normal, caused by the failure of carrier current radiation and the consequent failure of energy in leads |28, recloses the operating circuit for the motor of the time delay relay I I4 through a path extending over the normal make contacts of relayv I I3. Relay ||4 will now cause the commutator |2| to continue its rotation until such time as contact ||9 leaves the particular operating segment on cam |20 associated with this station and breaks electrical contact with the commutator, at which time the motor will come to an automatic stop and will maintain this condition until the entire system is shut down, at which time it will return to normal and contact ||9 and cam |20 will be restored to the'position shown in the drawings. As a consequence of the opening of the electrical circuit between contact I9 andthe particular operating segment on cam |20, current will be removed from leads |22 and the holding windings of relays |00, |0I, |06 and |01 and these relays will return to normal. The return to vnormal of relays |00 and I0| will cause the respective armatures thereof to be drawn to their right-hand positions by their restoring springs, and will connect the transmission lines |23 and |24, respectively, to the right-hand blades of

switches

22 and 23, respectively, and to the amplier equipment comprising preamplifier 65 and power amplifier 61 with their respective plate and filament supply circuits 14 and 10, The restoration of relays |06 and |01 to normal will close their normal break contacts to provide a path for the power supply through the central contacts of relay I|0 and through the normally made normal break contacts of relays |06 and |01 and through switches I9 and 2|, respectively, in their prescribed position, to the plate and filaments of the electron discharge devices associated with the spare amplifier.

In the event that the second relay station in the relay system does not begin to supply radiation because the normally selected amplifier does notfunction properly, the cam |20 at this station will continue to rotate until the end of #3 segment is reached when the electrical circuit between contact IIS and commutator |2| will be opened, and the spare amplifier at this station will be thrown into service. The cam |20 at the first relay station, however, will be stopped in the midposition of #l segment. As soon as radiation occurs from the second relay station, the signal coming through the second relay station will stop all subsequent stations at the #3 segment position on their respective cams.

In the event that the third relay station in the system does not begin to supply radiation because the normally selected amplifier does not has gone before that the iirst tworelay stations will have stopped` in the midposition. of the #l segment on the cam, while the third station as well as the subsequent stations will advance to the end of the segment position. At the end of the #5 segment position, the spare amplier at the third relay station will be thrown into service and the radiation of signal therefrom will stop the cams at the subsequent stations.

The table below shows the position of the cams at the several repeater stations under various function properly, it'will be apparent from what 75 At start only relay sta- Relay station #l Relay station #2 Relay station #3 Relay Relay station #4 station #5 Start with tone A-no failure tion #5 falls At start only relay station #4 fails At start only relay station #3 fails At start only relay station #2 fails At start only relay station #l fails I f all start O. K. and

then station #5 fails If all start O. K., and then stations #5 and #4 fail in succession 1 1 1 9 If all start O. K., and then stations #5, #4 and #3 fail in succession If all start O. K., and then stations #5, #4, #3 and #2 fail in succession 1 3 5 9 If no station starts O. K 2 3 5 9 If all start O. K., then station #4 fails l 1 1 9 9 If al1 start O. 'K., then station #4 and then station #3 fails l l 5 9 If all start O. K., then station #4, then station #3, then station #2 fails 1 3 5 g If all start O. K., and then stations #4, #3, #2 and #l fail in success1on 2 3 5 9 If all .start O. K., and stations #4, #3, #2, #l and #5 fail in succession 2 3 5 9 From the foregoing, it will be seen that the starting tone A starts all the cams at the various repeaters together, but the signal coming through stops the cams.

One advantage of the present invention lies in the fact that if the diode current in diode 18 fails in any one repeater station, causing a transfer to the spare amplier, the subsequent repeater stations in the direction of transmission Y need not transfer to the spare amplifier.

In the event that the public service power supply fails either completely or falls below a minimum prescribed voltage determined by the under-voltage relay 24, the relay will return to its normal position and the emergency or spare power supply comprising rotary converter 30 and battery 3| will be connected to the system through a path including the positive terminal of battery 3|, through lead |29, through armature and field in parallel of rotary converter 30, lead |30, intermediate break contacts of relay III, lead |3I, right-hand operated contact of relay IIO, lead |32, meter 32 to the negative terminal of battery 3|. The emergency or spare power supply equipment will pass power through leads |33 and closed switch 35, leads |34,A and normally made or breaky contacts ofy relay III to voltage. regulator. 28 and then over acircuit previously` described to relay I it for. supplyingA power to theY plates and filaments of theV amplifiers. Thechange-over from the public power supply tothe emergency supply is designed to be so rapid upon failure of the public service power supply that the relays maintain their normal operating vpositions without any interruption whatever,.due to thechangeover. As soon asthevoltage. on the public service supply becomes normal, a change-over is again effected from the spare or emergency power supply to the public service supply by the operation of relay in a manner previously described. While the. system is on the public service power supply, the battery 3| is kept charged through VRectox unit 29 and` its associated transformer 29a and the enclosed switch 34. This chargingis regulated by the ampere-hour meter 32.

If the division center desires to know the status .of the apparatus at the repeater station, a

' tone ,C will be sent out over the service circuit and passed through selector 53 to be amplified and rectified at 'l2 in order to operate relay |95, the. latter upon operation closing its contacts to operate motor 25 over a path including leads |35 which extend to the, alternating current powersupply. A plurality of code Wheels 65 are secured to the shaft driven by the motor and function in a manner similar to that described in Fig. 2 to send out code signals indicative of various conditions at the repeater station. The codesegments selected by the code wheels a', b', c', d', e' and f cover predetermined non.- overlapping sections onV the periphery of the code wheels, each code wheel sending out a characteristic signal indicative of the condition of a particular piece of equipment at the repeater station. Considering code wheel a.' as an example, this code rwheel will indicate whether or not diode I8 is functioning in response to a minimum normal of radiation. If normal radiation is occurring, the output from diode i8 will operate relay in a manner previously described and close a. circuit over its contacts and over leads |36 Vand through thecode wheel to operate relay ||2, this last relay, in turn, operating keyer 2l to transmit a characteristicV signal over lead |31 extending to the service circuit. Code wheelY b functions to indicate whether or not there isa noise level at the repeater station above adesired normal. For this purpose there is provided av` relay |99 which is connected in the outputy of.4

converter and rectifier 79, the latter in turn being connected to a suitable pick-up transmission line |26 coupled to the output transmission line |24. This noise level status can only be determined when. the division center removes modulation from the carrier. Converter and rectifier 9 is a balanced detector circuit and therefore only supplies rectified current to relay m9 when there is-modulation on the carrier. Obviously, if modulationis removed by the division center, the only modulation which can operate relay |09 will be that-produced by noise. The contacts of relay |09 are connected through leads |38 to the disc wheelb to cause operation of relay ||2 when the segments on the disc wheel b are engaging the spring contact associated therewith. Code wheel-c' indicates when relay is operated and consequently that public service power supply is connected to the system, while code wheel d indicates when relay is normal and consequently that the emergency or spare power contacts areemployed in order` that theV divisifln center may be given a positive indication at all times of whether one or the other of the power supply equipment is being used, Code wheels e' and f serve to indicate which set of amplier eqmpment is being used. For example, if amplifiers 64 and 66 are being used, the switches it. and 2Q will bedown (assuming the conditions prescribed above), relay |66 will be operated and leads |39 from code wheel e will be closed through the contacts of this relay. However, if the spare amplifier set comprising 65 and 61 is being used underfthe conditions prescribed above, then relay I will be restored to normal and a path will be closed over leads |40 and the normally closed contacts of relay |66 to cause code wheel f to influence relay H2. It will be seen from an inspection of the drawing that the shaft of the motor 25 is maintained at apositive potential and that the code wheels directly mounted thereon are also maintained at this potential, while a bus MI directly connected to the coil ||2 is common to one contact of the various, pairs of contacts associated with the respective code wheels. As in the case of Fig. 2, the motor will come to rest at the position where all contacts to the code wheels are open.

When it is desired to shut down the repeating station, the division center will send out a tone. B which will be received over the service circuit and passed through selector 62 and am-f plied and rectified at to operate relay H33. The operation of this relay will break its normally closed contacts to open the return circuit of the magnet coil of relay H0, thus restoring relay HSB to normal. The restoration of this relay to normal removes power supply from the lsupply equipment is functioning, Both of these plates and filaments of the amplifiers which passed through the operated contacts of this relay. 'Ihe right-hand contacts of relay l0 will now be opened, thus opening the circuit of leads |3| and |32 to prevent the operation of vrelay and insuring that the emergency power supply does not start up when the station is not in operation. The return to normal of relay |||3 will also cause all the relays in the circuit to return to normal. It will thus be obvious that the shut down signal provided by tone B will set all relays so as to prevent the necessary functions of the apparatus at this station until the starting tone Ais again applied.

By the term timing used in the appended claims, I refer to the timing of the occurrence of similar portions of successive waves. If the frequency is changed, the time between successive similar portions is correspondingly changed. Or, if the phase of a wave is shifted, the time of occurrence of any wave portion is made earlier or later than in the absence of such phase shift. Thus, the term timing modulation includes both variation of frequency and variation oi phase. In contrast to this, in the case of amplitude modulation the timing of the occurrence of similar portions of successive waves is unaffected by the modulation.

What is claimed is:

l. In a radio relaying system, a first station, a remote second station, and an intermediate station for relaying signals between said first and second stations, said intermediate station comprising a radio relaying station having two sets of apparatus for alternatively performing the same function, and circuit means at said station responsive to a predeterminedl signal arriving over one ofsaidother stations for -transmitting a characteristic signal indicating which one of said two sets is performing its intended function.

2. A relaying station for radio waves comprising a transmitting antenna, two amplifiers, and means responsive to a predetermined signal received by said station for automatically radiating over said antenna a characteristic signal indicating which amplifier is operatively associated with said antenna, there being different characteristic signals for said two amplifiers.

3. A relaying station for radio waves, electron discharge device equipment at said station, two 4 sets of power supply apparatus, and means responsive to a predetermined signal received by said station for automatically radiating a characteristic signal indicating which set is operatively associated with said electron discharge device equipment, there being different characteristic signals for said two sets of power supply apparatus.

4. A relaying station for radio waves comprising a transmitting antenna, two amplifiers, two sets of power supply apparatus for said amplifiers, and means responsive to a predetermined signal received by said station for automatically radiating over said antenna characteristic signals in sequence and in a predetermined order indicating which amplifier is operatively associated with said antenna and which set of power supply apparatus is operatively associated with the said amplifiers, there being different characteristic signals for said amplifiers and sets of power supply apparatus.

5. A radio relaying system comprising a central office, a remote station in said system, said remote station having two sets of apparatus for alternatively performing the same function, and circuit means at said remote station responsive to a predetermined signal from said central office for transmitting to said central office a characteristic signal indicating which one of said two sets is performing its intended function.

6:. A radio transmitting station having two sets of apparatus for alternatively performing the same function, a motor, a selector responsive to a predetermined signal for operating said motor, a shaft for said motor, a pair of code wheels on said shaft, said wheels being equipped with elements around the periphery thereof providing different codes for said sets of apparatus, contacts for each code wheel for engaging said elements, circuit means under control of the contacts on said code Wheels for transmitting characteristic signals corresponding to the codes on said wheels, and relay means controlled by at least one of said sets for determining which one of said code wheels will operatively affect said circuit means through its associated contacts, whereby the transmitted code signals indicate which one of said two sets of apparatus is performing its intended function.

7. A radio transmitting station having an amplifier and also a spare amplifier, power supply apparatus and also an emergency power supply apparatus, a motor, a selector responsive to a predetermined signal for operating said motor, a shaft for said motor, four code wheels on said shaft, one for each of said ampliers and power supply apparatus, said wheels having different codes provided by segments, the segments on the code wheels associated with said amplifiers being located on substantially the same 180 portion but oppositely with respect to the segments on the code wheels associated with said power supply apparatus, contacts for each code wheel, circuit means under control of the contacts on said code wheels for transmitting characteristic signalsV corresponding to the codes on said wheels, relay means controlled by at least one of said amplifiers and additional relay means controlled by at least one set of said power supply apparatus for respectively determining which code wheel associated with said amplifiers and which code wheel associated with said power supply apparatus will effectivelyV operate said circuit means to cause the same to send out the desired characteristic signals upon rotation of said shaft.

8. A radio relaying system including a transmitting station radiating amplitude modulated Waves, a repeating station for receiving said radiated amplitude modulated waves, there being means at said repeater station for changing said amplitude modulated waves to frequency modulated waves and for radiating said frequency modulated waves, and a receiving station for receiving the frequency modulated waves transmitted by said repeating station.

9. A radio relay system for use at ultra short wavelengths comprising a transmitting station radiating amplitude modulated waves, a repeating station receiving said amplitude modulated waves and converting` them to frequency modulated Waves having a different wavelength and for radiating said last waves, a second repeater station for receiving the waves sent out by said first repeater station, means at said second repeater station for converting the received frequency modulated waves to frequency modulated waves of a still different Wavelength and for transmitting Waves of said still different wavelength, and a receiving station for receiving the waves transmitted by said second repeater station.

10. A radio relaying station comprising an electron discharge device amplifier, power supply equipment, means responsive to a predetermined signal for connecting said power supply equipment to certain electrodes of said amplifier for conditioning the same to operate, means responsive to 'another predetermined signal to disconnect said power supply equipment from said amplifier, and` means responsive to a third and different predetermined signal tor cause said station to transmit a signal indicative of the status of said amplifier.

11. A radio relay station comprising an electron discharge device amplifier, public service power supply terminals and spare power supply terminals for said station, means at said `station responsive to a predetermined signal for connecting said amplifier to one of said power supply terminals, means at said station responsive to another predetermined signal to disconnect said last power supply terminals from said amplifier, and means responsive to a third and different predetermined signal to cause said station to transmit a signal indicating which of said power supply terminals is connected to said amplifier.

12. A radio relay station comprising a receiving element, a transmitting element, amplifier apparatus adapted to be connected between said elements, and means responsive to a predetermined signal for causing said station to transmit a characteristic signal indicating whether the noise at said station is above normal, said means including radio frequency pick-up apparatus coupled to saidtransmitting element and a converter'and rectifier coupled to said pick-up apparatus.

13; A radiorelay station comprising a receiving element, a transmitting element, amplier apparatus adapted to be connected between said elements, and means responsive to a predetermined signal for causing said station to transmit a characteristic signal indicating Whether the noise at said station is above normal, said means including the following elements: a radio frequency pick-up apparatus coupled to said transmitting element, a converter and rectifier coupled to said pick-up apparatus, a motor, a selective circuit passing only said predetermined signal for operating said motor, a code wheel driven by said motor, a circuit operatively responsive to modulating energy in said converter and rectier and linking said converter and rectier to said code wheel, and keying means responsive to the rotation of said code wheel.

14. A radio relaying station comprising a receiving antenna, a transmitting antenna, a pair of ampliers adapted to be alternatively connected to said antennae, relays for controlling the operative association of said amplifiers with said antennae, said relays having holding coils, and means responsive to the reduction of radiation from said station below a predetermined minimum for switching said amplifiers, said means including a radio frequency pick-up member, a rectier coupled to said pick-up member, and connections from the output cf said rectifier to the holding coils of said relays, whereby reduction of current in the output of said rectifier below said predetermined minimum reduces current in said holding coils and releases said relays.

15. A relaying station for radio waves comprising a transmitting circuit, two amplifiers, and means responsive to a predetermined signal received by said station for automatically sending over said circuit a characteristic signal indicating which amplifier is operatively associated with said circuit, there being diiierent characteristic signals for said two ampliers.

16. A relaying station for radio waves, electron discharge device equipment at said station, two sets of power supply apparatus, and means responsive to a predetermined signal received by said station for automatically transmitting a characteristic signal indicating which set is operatively associated with said electron discharge device equipment, there being different characteristic signals for said two sets of power supply apparatus.

17. A radio relaying system including a transmitting station radiating amplitude modulated waves, a repeating station for receiving said radiated amplitude modulated waves, there being means at said repeater station for changing said amplitude modulated waves to waves modulated as to timing and for radiating said last waves, and a receiving station for receiving the Waves transmitted by said repeating station.

l0 18. A radio relaying system including a transmitting station radiating amplitude modulated waves, a repeating station for receiving said radiated amplitude modulated waves, there being means at said repeater station for changing said amplitude modulated waves to shorter waves modulated as to timing and for radiating said last Waves, and a receiving station for receiving the waves transmitted by said repeating station.

Y 19. A radio relaying system including a transmitting station radiating amplitude modulated waves, a repeating station for receiving said radiated amplitude modulated waves, there being means at said repeater station for changing said amplitude modulated waves to frequency modulated waves of shorter Wavelength than the received amplitude modulated waves and for radiating said frequency modulated Waves, and a receiving station for receiving the frequency modulated Waves transmitted by said repeating station.

20. A radio relay system for use at ultra short wavelengths comprising a transmitting station radiating amplitude modulated waves Whose length is of the order of six meters, a repeating station receiving said amplitude modulated waves and converting them to frequency modulated waves having a shorter wavelength below one f meter and for radiating said last waves, a second repeater station for receiving the waves sent out by said first repeater station, means at said second repeater station for converting the received frequency modulated Waves to frequency modulated Waves of a still different wavelength but also below one meter and for transmitting waves of said still dilerent wavelength, and a receiving station for receiving the waves transmitted by said second repeater station.

FRED H. KROGER.