Title:
Radio control system
United States Patent 2469539


Abstract:
This invention relates to radio communication systems and more particularly to the remote connection and control, over a line from a master station, of a desired one of a plurality of distantly located radio stations each comprising either a receiver, or a transmitter, or both. A feature of...



Inventors:
Abbott, Henry H.
Bascom, Henry M.
Fairlamb, Preston B.
Application Number:
US64958246A
Publication Date:
05/10/1949
Filing Date:
02/23/1946
Assignee:
BELL TELEPHONE LABOR INC
Primary Class:
International Classes:
H04W84/02
View Patent Images:
US Patent References:
2176868Radio communication system1939-10-24
2101668Radio communication system1937-12-07



Description:

This invention relates to radio communication systems and more particularly to the remote connection and control, over a line from a master station, of a desired one of a plurality of distantly located radio stations each comprising either a receiver, or a transmitter, or both.

A feature of the invention resides in means, including permutation code transmitting apparatus,.at a master station for selectively control.ling, over a line, the operation of selector apparatus located at the. several radio stations to connect the input circuit of any desired one of a plurality of radio transmitters to a common communication channel terminating at the master station.

Another feature resides in means including said code transmitting apparatus and selectors for selectively conditioning the selected radio transmitter to transmit on any desired one of a predetermined plurality of frequency bands.

A further feature resides in means also including said code transmitting apparatus and selectors for selectively conditioning desired ones of said radio receivers to respond to desired ones of a predetermined plurality of radio frequency bands.

A still further feature.resides.in means including said code transmitting apparatus and selector for selectively-and individually disconnecting desired ones of said receivers from the communication channel.

Still another feature relates to insuring reliable operation of the system by requiring the transmission of two successive codes, in a predetermined sequence, to effect the desired control thus obviating false and improper control of station and frequency selection due to false line impulses caused by accidental line grounds and crosses, crosses with other electrical circuits, false relay, operation, etc.

Another feature resides in means also controlled by said code transmitting apparatus and selectors, responsive to energization of a telephone transmitter associated with the communication channel at the master station, for causing the radiation of the radio signals from the selected radio transmitter and disabling all radio receivers connected to the channel and responsive to the deenergization of the telephone transmitter for deenergizing the selected radio transmitter and reenabling all connected. receivers.

Other features of the invention will be apparent from the following.description when read in connection, with the accompanying drawings: Figs. 1 and-.2 of which, when placed side by side with Fig. 1:to ithe left of 'g. 2, show ;the arrangement of apparatus:and bircuit at a master or control istation rconnected over a..pair of lines to a plurality, (six) ofdistant radio station locations two of which; stations I and' 6 are shown on Figs. 3:. and: 4.; Referring 'to the drawing, ,ig. 1 shows a telephone .for use -by ýan attendant (dispatcher) at the master or control station, a iplurality of groups of selector keys for selectively initiating the desired control at tthe. desired radior station, and a start-stop code transmitting; distributor.

Fig. 2 shows the .relay equipment ,at the master station associated with the distributor :shown in Fig. 1 and -igs.. 3 :andA4 show a ,non-typing:selector at one of the stations (station :) . and circuits therefor; to control a .combined;: radio transmitter and receiver in accordance with codes transmitted from: the master station.-: An additional.station 6 of the system, similar.rinall respects to the.-first station, is indicated ;inr:the upper right-hand corner of Fig. 4.

In describing the operation of the system, from which an understanding, of the invention- may obtain, it will be understood that the attendant's, i. e., the dispatcher's telephone at the masteror control station is adapted to be- connected-to .a speech -communication line.,L which extends -to a plurality of distant radio station locations; as for example, stations I -and 6 shown in Figs. 3 and 4, and that the output circuit of the radio receiver at each-of the stations is connected to line L, and one of the .receivers, for example: at station I, is conditioned to receive -on one of the frequencies for which itis adapted, frequency I for example, whereby, the attendant is able to monitor on the line, i. e., listen, Now let it be assumed that the dispatcher, after listening on -the line, desires to transmit from the transmitter at station I on frequency TFI.

He therefore selects the desired radio transmitter by depressing the transmitter selecting, key SI which locks, and selects-the desired transmitting frequency 'by depressing the frequency key. TFI and, thereafter, momentarily operates 'he nonlocking code start key TST' (ig. 2): whereupon relay TS operates in a circuit from battery, winding of TS, right-hand- contacts of TST, contact I of receiver start key RST, -through similar contacts of the receiver tart keys for receivers 2 to 5, inclusive, .as iindicated 'by ,the broken line 2, contact'3 of receiver start key RST6, and contact 4-of relay;G to ground.u Relay TS-operates and closes its contacts 5 4to operate relay W ,of a :so-called: "W-Z" combination, in a circuit from battery, resistance 6, winding of W and contacts 7 thereof, contacts 8 of relay G, contacts 5 of relay TS and contacts 9 of relay 10 (Fig. 1) to ground. Relay Z is short-circuited at this time by the connection of ground to both ends of its winding.

Relay W in operating closes its contacts 1 to complete a locking circuit for itself from ground, contacts 12 of relay PW contacts 13 of relay PZI, contacts II and winding of W and resist- 1 ance 6 to battery.

Relay W also closes its contacts 14 to close a holding circuit for relay TS which is completed from ground over contact 12 of relay PW, 13 of PZI, contacts 14 of W, lower front contacts and winding of TS to battery. Further, relay W closes its contacts 15 to operate relay G in an obvious circuit. Relay G in operating closes its contacts 16 to operate the release magnet 17 of the distributor D (Fig. 1) in a circuit from ground, contacts 18 of W,.contacts 19 of relay Z, contacts 16 of G and winding of magnet 17, whereupon the stop latch 20 of the distributor, which normally holds the distributor brush 21 in contact with the stop segment 22, releases the brush and it starts to revolve under the influence of motor 23 which it will be assumed is in operation but prevented from rotating the brush shaft due to slipping of clutch 24. When the brush 21 leaves stop segment 22 and passes onto "start segment" 52, which latter segment has no connection to the key and relay equipment at the master station, ground is removed from relay 10 which relay thereupon releases and opens its contacts 25 thereby opening the normally closed telegraph or signal line TL which serially includes line battery LB and during the interval the brush is passing over segment 52, the line TL remains open and the receiving magnets associated with the selector at the various distant radio stations, such as magnet R at station I (Fig. 3), releases.

Release of relay 10 also opens its contact 9 thereby removing the ground previously applied to the left-hand end of the winding of relay Z and this relay thereupon operates in a circuit from ground, contact 12 of relay PW, contact 13 of relay PZI, contact II of relay W and winding of Z and resistance 31 to battery.

Now if the code required to select the transmitter at station I requires a marking impulse during the contact of the distributor brush with segments 26 and 27, then leads 26 and 27 from the distributor will be connected to terminals 32 and 33 of key SI of the row of transmitter select keys and in like manner if the code required to condition the transmitter at station 1, to transmit on the desired frequency (TFI), consists of two marking pulses caused by contact of the distributor brush 21 with segments 26 and 28 then lead 26 will be connected to terminal 35 of transmitter frequency key TFI and lead 28 will be connected to terminal 50. Further terminals 36 and 37 of key SI will be connected to terminals 38 and 39 of relay TS (Fig. 2) and terminals 43 and 131 of key TFI will be connected to terminals 44 and 51 of the same relay.

Other connections, in various combinations, between the distributor D and the terminals of the other select keys of Fig. 1, and between these keys and switching terminals of the relays of Fig. 2, will be made to transmit over line TL, the characteristic codes required, as hereinafter discussed, to effect the desired controls which will be understood to those familiar with teletypewriter systems.

Now continuing with the description of the operation of the system, when the distributor brush, now in motion, moves off segment 52 and makes contact with the first transmitting segment 26, ground is applied thereto and an energizing circuit for relay M is closed over lead 26, terminal 32, closed contacts 45, and terminal 36 of key .0 SI, terminal 38, and contacts 46 of relay TS (Fig. 2), contacts 47 of relay W, now operated, and winding of relay M to battery which latter relay now operates and recloses the line TL, which was opened when relay 10 (Fig. 1) released at the beginning of the code cycle and reoperates the selector magnets such as R at the different stations, which magnets control the closure of contacts of the selector.

During contact of the distributor brush with 0o segments 26 and 27, relay M remains operated, and the line TL closed, thereby transmitting the predetermined code for which the selector S is adjusted, thus closing its contacts 53 which operate the transmitter start relay 54 at station I which relay opens its lower back contacts and closes its front contacts in preparation for the next code transmitted which determines the frequency on which the transmitter is to operate.

Operation of relay 54 closes an upper contact to prepare a circuit for relay 55 when relay 56 is energized. When the distributor brush moves off segment 27, relay M releases thereby opening the line TL and when the brush completes its first revolution, and engages the stop segment 22, relay 10 operates which closes its contacts 25 to again close the line TL. Relay 10 also closes its contacts 8 to connect ground over contacts 5 of relay TS and the front contacts of relay Z to short circuit relay W which thereupon releases.

,0 Release of relay W at this time, however, does not open the circuit for, and release, the latch magnet 17 associated with the distributor for the reason that an alternate circuit for magnet 17 is closed at contact 57 of relay W and contact 58 of relay Z. Further the release of relay W does not open the holding circuit of relay TS due to the operated condition of relay Z.

Due to the continued energization of relay 17, the distributor does not stop at this time and as soon as the brush moves off start segment 52 another code is transmitted to operate the selector at station I to adjust the transmitter thereat for the desired frequency, as determined by the operation of transmitting frequency key TFi which codes consist of an impulse when the brush passes over segment 26 and another when it passes over segment 28, relay M being controlled at this time over contacts 59 and 60 of relay TS and contacts 61 and 62 of relay W now released. When the distributor brush moved off the stop segment 22, relay 10 released thereby removing the ground which had been holding relay Z operated and this relay then released thereby releasing, at its contact 76, the holding circuit for relay TS which released. Sending the transmitting frequency code on the second revolution of the distributor causes the selector S at station I to close its contacts 63 to operate relays 64 and 56 over back contacts 66 of relay 67 and front contact 68 of relay 54, lower winding of relay 64 and winding of relay 56 to battery. Relay 64 opens its upper back contacts to release any succeeding relays which may be operated and by closing its upper and lower front contacts locks itself over its upper winding and the series chain 4i34e9,8s9 S Jof lower: contacts toT:battery-on'theinnedlower armature of relay 69. Operation of relay 64tlso :closes its lowermost contact ftherebyýconnecting :ground- to :the lead 10. to condition: he trans:mitter to transmit on the desired-frequency, i. e., fl.

Operation of relay 56 completes a. circuit. to Soperate relay. 55 -which; was. prepared :'by- the Soperation of relay 54.

Relay 55 closes its contacts to lock-itself oper--.10:ated under control of :relays37 3:and-'69. ' Operation of relay .55 also :connects, the-input:of the Stransmitter to the line-L and by:'closing.its:.con-tacts 10l -prepares -a -:circuit _to; energize ,ýt e Scarrier control lead.:l75: when. the- dispatcher at ::the master station energizes his telephone trans:mitter -by ::pressing -the :"press :-to :talk" 'key 76 which. will be- later:referred: to. ::It:will be noted: that at-'station- I, selector contacts 125, 126 aind '127,' 1-28 -i~and' strapped together and connected to relay" 130 'whereas contacts 53 are connected to relay 54.

While not shown it will be understood that at station 2, for example;,contacts 125'will-be connected to the relay at that station corresponding :25 to relay 54 and the contacts .53, 126, 127, 128 and 129 will be strapped and connected to the relay corresponding to relay 130. At station 3, :contacts 126 will be connected to the'relay 54 and so on.

It will therefore be obvious that when a. code *,is transmitted; to close contacts 53 at station I, corresponding contacts at the other stations will be closed to operate relays-corresponding to relay 130 and when the succeedingcode- was 35 transmitted, it closed- contacts' 63 and: operated relay 64, and simultaneously this same code will also operate selector contacts corresponding to - 63 at station 2, and succeeding stations, and due to the fact that the relays of these other sta-- 40 tions, corresponding to relay 54 are not "operated, circuits at the other stations will- be completed over back contacts of 54 and'front contacts of 'relays 130 to operate the-corresponding release relay 73 which will release-relay i55, if operated, and disconnect and disable the transmitter ' which at the time is connected to line L.

It will now be understood -that :the selection and connection to the line of the desired transmitter has - been effected andd also the trans-"'50 - mitter has been conditioned to transmit on'frequency f. Now when the distributor completes its -second revolution and the brush engages the stop segment 22, ground will-be applied to relay *10 which operates and closes its. contacts 25:'' :to close the line TL, as previously described.

SRelays W and Z are now released which-was their *original condition.

the proper transmitter selection code impulses Receivers at stations -I and 6 set to 'l;"O receive on frequency -2 - is effected unless there immediately follows,- beIt will be further assumed that the dispatcher at.the time of making the original selection-of the radio transmitter at. station 1: also des to condition the radio receivers at stations I and 6 to receive on frequency /2 which receivers.at that time were conditioned to reeeive on: fre-quency fi and the dispatcher therefore depressed Sreceiver frequency. keys RF: for, stations I: and 70 .O 6. which keys. in operating, release in a well.known manner, the- keys RFi ý which. we:.have assumed were. previously loperated. :The ::dis-patcher now operates receiverS startnkeys' RSTI -and: RSTe .in_: succession. Operation :of, RSTi ýacloses:-, a'circuit to:roperate:.relayRSr which.-is :Atraced Ifrom .battery, winding Cof:RSi, contacts -.71 of key RSTi, contacts; 3 :of key RSTe6 before `this-key is operated, to ground over contacts: 4 of relay G. Relay RSI in operating closes its contacts 78 to operate relay W in a circuit from ground, over contacts 9 of relay 10, contacts 78 -bf relay RSi.and contacts 8 of relay G and con-tacts: 7 bf-relay W. ~ Relay W in operating locks itself and relay. RSi to ground over contacts 12 of relay PW and operates relay G thus energizing the latch magnet 17 of the distributor, whereupon the distributor starts to revolve and sends code. pulses over the line TL as determined by 15- the receiver frequency key now operated. From this point on the operation is the same as before .described. for sending the transmitter selection - and transmitter frequency code, i. e., on the first :revolution of the distributor ground will .be -are 20- applied to certain upper contacts- of relay RS1, determined by the operated key RF2, and the wiring therefrom to the relay contacts which will control the relay M over the front left contacts of relay W now operated, and on the second revolution, at which time relay W is released as previously described, a different code will be transmitted as determined by the wiring between the key RF2 and the lower contacts of relay::RSi.

The first code sent, on the first revolution of the distributor, we will assume actuates the selector at station I to close its contacts 79 thereby :operating relay 67 which in operating: closes -its left-hand contacts in preparing for the immedi-'ately following -code which we will assume causes the selector to close its contacts 80 there:by 'completing a circuit to operate relay 81 in a -.circuit including contacts' 82 of relay 671 and lowermwinding of relay 81 to battery.

-Relay 81 operates and opens at its contacts 84:the locking circuit for relay 85, which we have -.assumed was-previously operated to condition the :'receiver ;at. station I to receive on frequency fi.

-Relay 81 .thereupon locks over. its inner front ';4:ontacts.and by closingý its contacts 86 connects ground, over conductor 87, to the radio receiver :which ,will perform the necessary switching functions to: condition it to receive on the de-:sired frequency f and to transmit the received signals to-the dispatcher's station over line L.

IThe same operation as just described is also -effected at station 6, the circuits of which are :not shown.

: After the distributor completes its second revo5'ution it stops as before described and the line TL is now closed and relays W and Z are in their normal released condition.

It will be noted from the foregoing that after are 'received at the station thereby operating -slow-release relay 54, no operation of relay 55 fore 54 releases, a frequency selection code to - operate one of the transmitting frequency relays ired:65:-such ;,as 64, 118, etc., which relays are controlled over: the front contacts of relay 54. Relay 56 :'operates:in series: with any one of the transmit':ting:: frequency relays and closes a circuit to operate! relay- 55 provided relay 54 is operated. urther, in case the dispatcher desires to con- trol any receiver frequency at a particular staI tion, the operation of any one of the receiver fre:'quencykeys:of the desired station causes. a pre,"-determined code to-be transmitted to close a con75ztct at the stationt tooperate wrelay;,suchas 67 at station I, which is slow-releasing. Following this code a second is immediately transmitted and if it is received before relay 67 releases, the desired frequency receiver relay such as 85, for example, will be operated. In other words, high reliability of the system is assured by requiring the receipt of two sets of selecting impulses in the proper sequence within a predetermined short time interval before a desired connection is effected or an established con- 1 nection is changed.

Dispatcher operates "press to talk" key With the radio transmitter at station I connected to the line L and conditioned to transmit 1 on frequency fi, and the corresponding receiver conditioned to receive on frequency f2, the system is now ready for communication and the dispatcher then actuates the "press to talk" key 76 associated with his telephone set, thereby closing 2 the circuit from battery through the telephone transmitter and relay 88 to cause that relay to operate thus closing a circuit to operate relay 89.

Relay 89 opens its lower contacts 90 and closes its contacts 91 thereby short-circuiting the righthand winding of relay PZ and operating relay PW which relay operates and locks and also closes at its contacts 92 a circuit to operate relay G which relay, in operating, closes its contacts I8 to operate latch magnet IT thus starting the distributor and thereby releasing relay 10 when the brush moves off segment 22. This opens the line TL and removes the short-circuit from the righthand winding of relay PZ which relay operates and holds to ground on the left front contact of PW.

Relay PZ closes its contact 83 to operate PZi which locks, opens its contacts 105 to open the circuit for the latch magnet 17 and also closes its contacts 94. If we assume that segment 26 is connected over lead 26 to terminal 95 associated with contacts 94, when the brush engages segment 26, relay M will operate to close the line to send a single pulse to operate selector magnet R and close contacts 96 of the selector. Prior to the transmission of this pulse, relay 48, which is in series with magnet R in the line TL, releases during the open interval of the line and due to the fact that relay 55 is operated at this time ground, over its contacts 74, is connected to the windings of slow-release relay 49 which thereupon operates and closes a circuit from ground, contact 71 of relay 49, contacts T9 of relay 98, contacts 99 of relay 100, and contacts 101, to energize the radio transmitter and put the carrier frequency on the air. This operation provides a very rapid energization of the transmitter at the first movement of the distributor, i. e., as soon as the distributor brush engages the start segment 52 and opens the line TL. Now when the line is closed by the first code pulse, relay 48 operates at the same time as the selector magnet R thereby opening the circuit previously closed to operate relay 49 and this relay is deenergized, but as its slowrelease characteristics are such that it holds for a short interval, during which time the selector contacts 96 are closed to operate relay 100, this relay locks and closes its contacts 102 thereby completing the holding circuit to maintain a ground connection to conductor 75 to keep the transmitters on the air. This circuit may be traced from ground, contacts 103 of relay 49 released, contacts 102 of relay 100 and contacts 101 of relay 55. Release of relay 49 after relay 100 operates completes a circuit to operate relay 98 which accomplishes no useful function at this time.

When the distributor completed its revolution and stopped due to the release of latch magnet S17, relay 10 reoperated thereby connecting ground over contacts 104 of relay PZ to hold that relay operated.

As long as the "press to talk" key 76 remains operated, thus holding relay 89, relays PW, PZ and 0 PZi remain operated at the master station.

At station I when relay 49 operated in addition to energizing the transmitter to put its carrier frequency on the air, this relay also closed contacts 106 to connect ground to conductor 107 to disable the radio receiver and when relay 100 operated and relay 49 released, a substitute circuit was closed to hold ground on conductor 107 to keep the receiver in stable condition. This can be traced from ground, contacts 109 of relay 49, con0 tact 110 of relay 100 to lead 107.

The radio transmitter at station 1 is now on the air and the corresponding radio receiver is disabled. The dispatcher at the master station now talks over the line L and the speech signals 5 are transmitted from the antenna. At the end of the speech transmitting interval the dispatcher releases the "press to talk" button 76 thereby releasing relay 89 which closes its contacts 90 thus shunting relay PW by connecting ground to the 30 right-hand terminal of its winding which can be traced from ground, contacts 9 of relay 10, contacts 104 of relay PZ and contacts 90 of relay 89 to the right-hand terminal of relay PW. This latter relay therefore releases and closes its con35 tact 12 thereby operating relay G which closes its contacts 16 to operate the latch magnet 17 of the distributor. This can be traced from ground, contacts 11I of relay PW, contact 112 of relay PZ, contact 16 of G and winding of magnet 17 to 40 battery. Latch magnet 17 in operating releases the distributor and when the brush moves off segment 22 relay 10 releases thereby opening its contacts 25 to open the line TL and by opening its contacts 9 releases relay PZ which closes con45 tacts 113 thereby connecting relay M to a predetermined segment of the distributor, for example, 28 by way of terminal 114 of relay PZ, whereby a single pulse is transmitted over the line TL when the distributor brush passes over seg50 ment 28. Relay PZ in releasing also opens its contacts 112 thereby releasing the latch magnet 17.

When the distributor completes its revolution, it stops on segment 22 and relay 10 reoperates thereby shunting relay PZi in a circuit to ground 55 from contacts 9 of relay 10, contacts 115 of PZ to the right-hand winding of terminal of PZi.

This relay now releases and releases relay G. Relays PW, PZ and PZi are now released in readiness for another operation cycle.

60 When the line TL was opened at the start of the distributor relay 48 at station I released thereby reenergizing relay 49 which operated, thereby opening contacts 103 to remove ground from the transmitter control lead 75 and also re65 opens its contact 109 to remove ground from receiver control lead 107 which thereby reenables the receivers.

When the last-described line pulse, caused by release of the "press to talk" key, is received, it 70 will be assumed that it causes selector S to close its contacts 116 thereby short-circuiting relay 100 which previously had been operated and locked.

Relay 48 reoperated at or before the first operation of the selector magnet R thereby deenergiz75 ing relay 49 which starts to release and finally 9' closes dits -bottomi contact at or before relay 100 releases' thereby completing a circuit to cause the release of relay 98. This, circuit can be traced from-: ground, contact- 11 7 of relay 1 00,- lower backi.contact 'of relay -49 to the right-hand terminal of:the winding of relay 98 which relay now releases and restores this-part of the station circuit, i. e., relays 100, 49 and 98 to normal.

Change' transmitting frequency If the dispatcher desires to transmit on a different frequency than the one originally selected, for example f2 he will depress transmitting frequency key TF2 which locks and automatically releases key TFi. Transmitting start key TST is then operated thereby starting an operation cycle to again transmit in the same manner as before described,; a pulse code determined by the still operated key Si of the row of transmitter select keys-to cause the distributor to control the selector at station I to again close its contacts 53 to -operate relay 54 and to immediately thereafter transmit the pulse code determined by the operation of transmitting frequency key TF2 to control the station selector to close its contact 80W to, operate -transmitting frequency relay 118 in series with-relay 56 which, however, performs no useful function if we assume that relay 55 is still operated.' Operation of relay 118 opens its contact 1I19 to open the holding circuit for relay -64 .which releases and by closing its upper back :contact-applies ground to lock relay 118.

Relay: 64 'removes ground from conductor 10 and relay , 18 -connects ground to conductor 120 thereby changing the transmitter to transmit on frequency -2.

Change receiver frequency If on:the other hand the dispatcher desires to change the receiver at station I to receive on the same frequency as that for which the transmitter is conditioned, i. e., fi, which it may be mentioned is-the most common condition, namely, transmitter and receiver sending and receiving on the same frequency; he -will operate the RFi key for station I thereby releasing relay RF2 which was previously operated.: He-will then operate receiver start key RSTi to cause a distributor to send the code to operate relay 67 and immediately thereafter sends- the code to operate relay 85. which releases relay 81 thereby connecting ground to receiver frequency lead 121 and removing ground from control lead 87 thus changing the frequency at which:the radio receiver at. station:1 -responds.

Disconnect the transmitter If the dispatcher desires to disconnect the transmitter from the line L at station I he will operate the transmitting frequency key OFF and hereafter actuate transmitter start key TST thereby initiating operation of relays TS, W, Z and G to cause the distributor to again transmit the code determined by the already operated key Si which causes the selector at station I to again close its contacts 53 to operate relay 54 and immediately thereafter to send the code determined by the operation of the OFF key thereby causing the selector to close its contacts 122 to operate relay 69 which releases relay 64 to remove ground from transmitter frequency lead 70 to disable the transmitter and to release relay 55 which disconnects the transmitter from the line and to also open the carrier control lead 75. The dispatcher can now select and connect another transmitter, if.'desired, lnthe manner originally; described.

Disable receiver 5 If :the dispatcher desires to disable any *radio receiver which may be in receiving condition, asfor example the receiver-as station I, he will press. the OFF key of the row of-receiver frequency keys for station I and thereafter, the receiver start key. .RSTi to initiate two revolutions of the distributor and the transmission of a code to first close selector contacts 79 at station I and thereafter a,: second code to close selector .contacts 122 to operate -relay 123 iwhich. relay opens the holding,, circuit 'for relay- 85 which releases and removes: ground ;from conductor 121. Relay 123,-in op-.erating, locks; opens its lowermost contacts to remove ground .from lead 124, and by closing- its:. uppermost contacts connects ground to conductor 107- to further disable the receiver.

From the-foregoing description it will be- seen that the system of the present invention enables the dispatcher, at the master station to controlby means of,the code distributor, selector keys . .and relay circiuts, any of the radio transmitters' and radio, receivers along the lines L and TL, i. e., (a) to connect any :transmitter to the line L to the exclusion- of any of-the others, (b) to condition the selected transmitter to transmit. .on .any one:of a number::of predetermined fre-quencies, (c) to condition: any number of the. radio receivers to receive on any one of a number of -predetermined frequencies.i (d) to conditionthe, connected transmitter for radio transmission.and to disable all 'of the radio receivers during the: interval the:: dispatcher's 'telephone :transmitter : is.:energized;:i. e. .while he is talking, (e)' and-to restore 'the. radi0o receivers to normal, receiving:condition and to deenergize the :connected radid,; transmitter (f. to disconnect'; any connected' radio transmitter fromA the- line and (g) to disablei any 'conditioned-radioý receiver: What is claimed is': 1. In: a station selecting system; in combina-tion,' a master station, a telegraph line extending: therefrom; a plurality of radio stations along said line, each station comprising a radio transmitter and a radio receiver, each' of said transmitters being adapted to be adjusted to transmit on any -one of a predetermined number of different radio frequencies and each receiver being adapted to be'* adjusted to:respond to any one of a predetermined' plurality of different received frequencies, a com,-' mon:communicationchannel extending-from the55- master: station td all of said radio stations, tele-' graph selector rapparatus- ini said telegraph lineindividual to the several radio stations, said telegraph selector apparatus adapted to respond to two successive and different codes initially, and start-stop permutation code transmitting apparatus adapted to transmit two successive and different codes initially, said code transmitting apparatus being selectively controlled at the master station and associated with the telegraph line for controlling said selector apparatus in different manners to selectively adjust any desired one of the radio transmitters to transmit on a desired one of said transmitter frequencies and to connect the input circuit thereof to said communication channel to the exclusion of any other transmitter, to disconnect any connected transmitter, to selectively condition a desired one of said receivers to resopnd to any desired one of said predetermined frequencies, to connect the output circuit thereof to the communication channel, and to selectively disconnect any connected receiver therefrom.

2. A system in accordance with claim 1, characterized by means for causing said code transmitting apparatus when started to complete two successive operation cycles and to transmit two respectively different codes and means at each substation responsive to the first of said two transmitted codes to prepare for the desired selective adjustment and responsive to the second transmitted code to complete said desired adjustment.

3. In a station selecting system, in accordance with claim 1, in which said master station comprises an attendant's telephone set connected to said communication line, said set including a telephone transmitter adapted to be energized and deenergized under control of attendant operated means, characterized by means responsive to energization of said telephone transmitter for causing said code transmitting apparatus to transmit a code to control the selectors in the telegraph line to simultaneously condition the radio transmitter, connected to the communication line, for radio transmission and to disable all said radio receivers, and responsive to deenergization of said telephone transmitter to cause the code transmitting apparatus to control said selectors to simultaneously decondition the conditioned transmitter and remove the disabling condition from said receivers.

4. In a station selecting system in accordance with claim 1 in which said master station comprises an attendant's telephone set connected to said communication line, said set including a telephone transmitter adapted to be energized and deenergized under control of attendant operated means, said start-stop permutation code transmitting apparatus being connected to the telegraph line to serve as a distributor after it has transmitted the codes to effect the desired selection at the radio station, said distributor being operated by the energization of the telephone transmitter and being adapted to transmit an initial pulse, means associated with the telegraph line and responsive to said initial pulse to energize the radio transmitter, and other means associated with said telegraph line responsive to said initial pulse to temporarily disable all said radio receivers and to simultaneously condition the radio transmitter, connected to the communication line for radio transmission, and responsive to deenergization of said telephone transmitter to cause a second operation of said distributor, said other means associated with the 5g telegraph line, responsive to the respective pulse, being effective to simultaneously remove said disabling condition from the radio receivers, and decondition the transmitter.

5. In a station selective system in combination, a master station, a telegraph line extending therefrom, a radio station comprising a radio transmitter and a radio receiver on said telegraph line, a communication line between said master and radio station, a selector apparatus associated with said telegraph line at said radio station, said selector apparatus adapted to make station and station frequency selections in response to two successive and different codes received over said telegraph line, switching means controlled by said selector for selectively and simultaneously conditioning said radio transmitter for radio transmission and for disabling the receiver, and for deconditioning the transmitter and enabling the receiver, a start-stop permutation code transmitting distributor at the master station adapted, when started, to transmit an initial open circuit pulse for conditioning said selector apparatus over said telegraph line, an attendant's telephone set comprising a telephone transmitter at said master station, attendant controlled means for energizing said telephone transmitter for speech transmission, means responsive to energization of said telephone transmitter to initiate operation of said distributor to transmit a code to control said selector to effect said simultaneous conditioning of the radio transmitter and disabling of said receiver and responsive to a subsequent deenergization of said telephone transmitter to initiate the second operation of said distributor to transmit code pulses to effect deconditioning of the radio transmitter and reenabling the receiver, and other means responsive to the open circuit start pulse, transmitted by said distributor at the start of its operation for temporarily conditioning said radio transmitter and disabling said receiver or deconditioning the transmitter and enabling the receiver, depending on their previous condition, until the selector responds to the code transmitted.

HENRY H. ABBOTT.

HENRY M. BASCOM.

PRESTON B. FAIRLAMB.

REFERENCES CITED The following references are of record in the file of this patent: UNITED STATES PATENTS Number 2,101,668 2,176,868 Name Date Bishop et al. -------- Dec. 7, 1937 Boswau ------------ Oct. 24, 1939