US1528011A

US1528011A - Radio signaling system

Info

Publication number: US1528011A
Application number: US683748A
Authority: US
Inventors: Charles S Demarest; Milton L Almquist
Original assignee: American Telephone and Telegraph Co Inc
Current assignee: AT&T Corp
Priority date: 1923-12-31
Filing date: 1923-12-31
Publication date: 1925-03-03
Anticipated expiration: 1942-03-03

Description

'Max'. 3. 1925.

c. s. DEMAREsT ET Al.

RADIO SIGNALING SYSTEM Filed D80. 31, 1923 2 Sheets-Sheet 1 1N VEN TORS A TTORNE Y Mar. 3. 19.25.

c. s. DEMAREST ET Al.

RADIO SIGNALING SYSTEM 1 Filed DeC 51'. 1923h 2 Sheets-Sheet 2 am W. 4 www 4 \M.|||I F e s.

A Si! WW 1 M n A u N ATTORNEY Patented Mar. 3, 1925.

UNITED ,STATES PATENT OFFICE.;

CHARLES S. DEMAREST, OF RIDGEWOOD, JERSEY, AND MILTON L. ALMQUIS'T, OF

BROOKLYN, `NEW YORK, ASSIGNORS TO AMERICAN TELEPHONE AND TELEGRAPH COMPANY, A CORPORATION 0F NEW YORK.

RADIO SIGNALING SYSTEM.

Application med December 31, 1923.A Serial No. 638,748.

To all whom t 'may concern."

Be it known that we, CHARLES S. DEMA- REsT and MILTON L. ALMQUTST, residing at Ridgewood and Brooklyn,in the counties of Bergen and Kings and Statesv of New Jersey and New York, respectively, have invented certain Improvements in Radio Signaliner Systems, of which the following is a speci cation.

This invention relates to radio signaling systems, and particularly to means for selectively signaling a particular station ofl such a system.

In the operation of a multi-station system, it is, of course, desirable that each station of the system shall be able'not only to.

paratus is designed. This will care for slight variations of ,the calling frequency sent from another station. of frequencies should not be too great else the apparatus will res ond to frequencies not intended for the ca ling of the stations of the system. In' the copending applicationrof Demarest and Almquist, Serial No. 646,903, filed June 21, 1923, is described a method and ineans for the transmission of a calling signal from one station to another of a multi-station system in which the high frequency carrier current is modulated by impulses of current of 135 cycles in accordance with a definite code and transmitted. At the particular station called, the modulated hi h frequency current is demodulated, an the impulses of 135 cycle current serve to Voperate a relay kresponsive to this frequency. While, of course, the relay may" be made to respond to other frequencies within a range extending, for example,

from 130 to 140 cycles, it 1s, of course, de-

'sirable to make the range as narrow as possible in order to prevent the operation of `other station of the system.

But therangethis relay by currents other'than the calling signaling currents transmitted from an- Any method, therefore, by which the sensitivity of the receiving set at 1'35 cycles may be increased will be of value. y

One of the objects of this invention is to increase the sensitivity ofthe receiving sets for calling signals, which object is obtained either by using a separate receiving set for the calling signals from that used in the reception of speech signals (each set being of maximum efficiency for the respective range of frequencies) or by using different connectons in a receiving set designed for the joint reception of the calling and speech signals, the lsaid receiving sets being designed to take advantage of certain conditions inherent in the reception of a particular low frequency signal.

A low frequency signaling system, such as the 135 cycle system referred to above, has the advantage that the'frequency of the s'de band is very close, to that ofthe carrier and therefore higher regeneration may be employed than is possible for speech reception (where the side band is fairly broad), the "regeneration being carried to a point very close to the oscillating condition.

AThis makes is possible to obtain maximum amplification through the use of the minimum number of vacuum tubes. The regeneration may be obtained -by plateand gridv tuning or by a magnetic feed-back as in the ordinary regenerative circuit. Since the increase in regeneration increases the sharpness of tunin and since the signaling apparatus, that 1s, the call responsive apparat-us, must be able to function at all times, it becomes necessary to keep the wave length of the transmitting station within narrow limits. A. device for controlling the trans-` mitted carrier frequency is shown in the copendin ap lication of yDemarest andAlmquist, eria No. 646,903, led June 21, 1923.

The present invention 1s concerned mainly nection with the attached drawing, of which -A Figure 1 shows an embodiment of the invention in which a single radio receiver functions for the detection of both the speech and the callingsignal, and Fig. 2 is a form in which separate receiving circuits have been' provided for the speech and the calling signals, each of which is highly etlicient vfor the particulai` frequencies employed. f

-In Fig. 1, which represents two stations A and B of a multi-station system, the transmitting antenna 1 at station A has connected therewith a radio transmitter 2, which may be of any well-known type, by means of which a carrier current may be modulated by speech currents and also by calling signal currents, and the resultant modulated waves may be transmitted to the other stations of the system. At station B the receiving antenna 3 is connected with the radio receiver 4 by means of the coupling transformer 5. The secondary winding of this transformer is connected with the grid and filament of the vacuum tube detector 7 the input circuit \including the condenser 6 whereby the input circuit may be tuned broadly to cover the range of frequencies to be received at station B and also including preferabl a grid condenser and leak. The output side of the detector 7, viz., the platelilam nt circuit, includes an inductance 8 whichis arranged dbe shunted by the operation of the relay 20. This'output circuit isconnected with the armatures of relay 10, the outer contacts of which extend to the calling-signal amplifier 11 and the innerV contacts of which extend to the speech-sigamplifier 15. The vacuum tube 13 of the amplifier 11 is connected `with the output of the detector 7 by means of the transformer 12. The condenser 9 is-of such value relative to the primary 'Winding of transformer `512 as `totune the circuit for 135 cycles so that the maximum gain will be at this frequency. The output side of the tube 13 is connected with the calling-signal apparatus 14, which may be either of the type disclosed inthe copending ap lication of Demarest and Almquist,'Ser1al,No. 646,903, cited heretofore,'or of any well-known type. The outvput side of the detector 7 is connected with the vacuum tube 17 of the speech-signalA amplifier by means of the transformer 16, and the output side of the tube 17 is connected with the telephone receiver or equivalent d evice 18. Relays '10 and 20 yare connected with the source-of current 21 and also with the receiver switchhook 19 in such manner that when the receiver 18` is upon the hook the circuit of the relays is open and remains deener 'zed until the receiver 18 is removed from t e hook of the switch v19. Battery 22 serves to provide the lilament heating current for all the vacuum tubes, and battery 23 provides the plate current for/tubes 7 'and lor the transmission of speech and calling signals from station B to other stations,

frSuch as A, of the radio system, a transmitting antenna 27 is provided having connectedV therewith .a radio transmitterI 26, which may be of the type represented by 2 of station A. Similarly at' station A a receivingantenna 28 having a radio receiver 29 connected therewith is provided, which radio receiver should preferably be similar to that represented by 4 of station B.

Having in mind the foregoing description of the parts of the apparat-usin which this invention is embodied, it will be clearly understood from the following description of the method ,of transmitting calling and speech signals, for example, from station A to station B.' Let it be assumed that a wave be transmitted from antenna 1' comprising a carrier and its side bands representing 'the carrier as modulated-by 1-35 cycley current. This modulated wave might be transmitted in accordance with a code in the manner described in the copending application of Demarest and Almquist, Serial No. 646,903, or might be an uncodedsignal. In any case the carrier and the side band would be received by antenna 3 Iand impressed by the transformer 5 upon the input circuit of the detector 7. The 135 cycle current resulting from detection would be impressed by the output circuit of the detector 7 upon the signal frequency amplifier 11. The 135 cycle current as amplified` by 11 would be impressed upon thecalling signal apparatus 14, and the operation of this' device would apprise the subscriber at station B that another station of the system desired to get in communication with him. -As pointed out heretofore, the inductance 78 in the output side of the receiver 4 is adjusted to tune the plate circuit to the point where it will almost oscillate at the radio frequency for which the set is tuned. By such adjustment,

the radio receiver is made highly regenery ative, thereby giving high amplification to frequencies'c'lose tothe carrier, such for example, as the frequencies obtained whenthe carrier is modulated by 135 cycles. In this manner, andalso by the use of an amplifier 11, which gives maximum amplication at 135 cycles, the receiving eiciency of station B at the fr uency of 135 cycles is materially improved. eqUpon the receipt -of the calling signal .at B, the subscriber removes his receiver 18 from the hook switch 19 which completes the circuit from battery 21 through rela s 20 and 10 and thereby operates these re ays. y lay 20, the inductance 8 is shunted and thereby effectively disconnected from the output-circuit of the detector 7. This actA detunes the output circuit of thedetector By the operation of re- -relay 10,

and decreases the re eneration'fto a point quencies connected with voice range, that is, 2 00 to 2,00Q`cycles.-

The arrangement shown in Fig. 2'rep'resents a system in which separatefradio ,ref ceivers are provided orfthe speech recep-' tion circuit and .for the signal reception cir-- cuit. In this ligure, transmitting antenna 40 and radio `1 :ransmitter-4J. correspondfto the elements designated 1 and 2.0i Fignl. At station B receivin'g antenna 42 isv lcon'-l .nected vwith the armatures" .of -relay's 43.

This antenna snormally connected with the signal reception circuit through.l the outer contacts of the said' relay. The `inner contacts `of this -relayserveto' connect' the antenna with the speech reception circ1'1it.- y A tuning condenser' 45 and a primary 'winding 46 of transformer '47 are connected meansv 'of conductors v44 and theouter contacts ofy relay 43 with the antenna 42 in order to tune contains a 35 the antennal for thefrequencies of thecalling signal. The secondary 48 of transformer47 is connected withjthe-'input'side of the vacuum tube detector' 50, andthe condenser 49'is connected across lthewindine'gj 48 in order to tune this circuit to the incoming The output side ofthegtube 40 feed-back winding. 51 in order to provide for 'regeneraton, and the cir-v cuit also contains the, rimary winding 52 frequency,

of transformer where y'tbezdetected com. ponent, that is, the 135 cycle current, will. be impressed vupon the input of the vacuum tube amplifier 57 by the transformer winding 54. The-primary winding 52 of trans former 53-'is tuned' to 135cycles"by the vconv l incoming high frequency currents as modulatv denser 58. The-output'circuitf of this tube -contains the primary-windingp) of trans# 'former 60, of which the secondary winding 61`is connectedwit'h the-.signaling apparaf ftus- 62'responfsi've tothe amplified 135'l cycle.

j The speech reception'sl'cii'cuitjincludes at lits input end the tuning condenser 69 1and .the primary winding 700i transformer 71 f whereby the antenna.- 42 may be.

' lthe particular range of currents'represented Pliner-represented bythe tube,v connecting circuit, a detector represented by the tube and its connecting-circuit, and .anv audiofrequency 'ampliiierrepresented e.

t" tuned antenna circuit is connected with the t vsideof tube74 by means of the-trans- -former 71, `the colmection including the secondarywi'nding 72 and theituning' `condenser the` speech frequencies. kv'Tliespeech Fre cep" the carrier tion circuit comprises a radio the tube 84y and its :connecting circuit.

v signal transmitte yed by the speech" by the high frequency amplifier A74 and will detector frequency' asf-modglgtgsl by i,

' plicantsinvention.

tube 84 the output side of which is connected bymeans of

windings

85 and 87 of transformer with the telephone receiver 88 is tobe `understood that common sources of current supply might beused in place .of the separate'sources shown on the drawing. Re lays 43 and 90, having connected therewith battery 91,l are designed to operate when ception` circuit. The loperation of relay. 90

vserves to connect the source of current- 98 With the filaments of the various vacuum'.

tubes in orderto energize the tubes.V

The output side of the detector is con- [nected by means ofthe

windings

81 and 83 "of transformer 82 with the input side of the receiver 88.fis removed from the switch- -hook 89. -Upon the operationof relay 43 *the antenna 42 will be connected by conduc- "tor 68 withthe input vside of the speech re` Since the signal reception circuit is norl mally connected by means -o conductors 44 with the receivin `tion- A will be impressedbyv the'tran'sformer antenna 42, the calling from antenna'40at sta- 47 upon the detector 50 which is designed to be regenerative., The detected-currents willbe impressed by transformerf53 upon,

the 135 cycle amplifier circuit,which is also designed to'give high'amplication at this particular frequency. The low lfre uencyI 00,

component will beimpressedby trans ormer '60 upon the signaling apparatus 62.` U on the receipt'of 'a calling-signal, the subscri er lat'station B removes 'his receiver 88 from .the hook of switch .89 which operates relays 43 and 90 thereby connectingtheA antenna 42 V with the speech reception circuit and also ener'gizing the vacuum tubes of the circuit. The

'ampliier and the resultant amplified hown at station B. f y

1- ngshould 2also 'bec-undergrad um time' 4w'ehave' shcwn only two stations, vthere are representatlve jofi lany z number g of stations' While this invention embodied in 'a particular vform, it`s` to be;

in other and different forms without departing from the spirit of the invention as defined in the appended claims.

lVhat is claimed is:

1. In a radio communication system, the combination with an antenna adjusted for the reception of a plurality ofiy bands of frequencies, of a radio receiver connected with the said antenna and comprising a vacuum tube detector having its output circuit so tuned that it will almost oscillate when.

the frequencies of one of the said bands are applied to the Said detector, an amplifier connected with the said receiver adjusted to give maximum amplification to one of the frequencies resulting from detection, and lan indicating device responsive to the low frequency.

2. In a radio communication system, the combination with an antenna adjusted for the reception of a plurality of bands of frequencies of a radio receiver containing a vacuum tube detector having its input cir-v4 cuit connected with 'the said antenna and having its output circuit normally connected with an amplifier designed to give maximum amplification of one of the said bands, a second amplifier designed to produce maximum amplificationof another band of frequencies and switching means to connect the said radio receiver with either of said ampliers.

3. In a radio communication system, the combination with a broadly tuned antenna of a radio receiver connected with the said antenna and containing -a vacuum tube detector whose input circuitv is ,tuned to cover the same range as the said antenna and whose output circuit is normally connected with an` amplifier designed for maximum amplification of certain of the received frequencies, the said output circuit being normally tuned to almost oscillate at the received carrier frequency, and switching means to detune the said output circuit` and to disconnect it from the said amplifier.

4. In a radio communication system, the

other frequencies received by said antenna,

and switching means to disconnect the' said output circuit from the said first amplifier and to connect it with the said second ampliier and also to detune the said output circuit.`

5. kIn a radio communication system, the combination with a transmitting station arwaves vand valso signal-modulated carrier waves, of a receiving station having an antenna tuned for the reception of both of said waves, a detect-or connected Ywith the said antenna,\a plurality of receiving circuits each designed for maximum eciency throughout the range of frequencies which each is intended to receive, and switching means to control the connection of the detector with each of the said receiving circuits.'

6. In a radio receiving System, the combination with an antenna of a vacuum tube detecting circuit connected therewith having its plate and grid circuits tuned almost to ranged to transmit speechvmodulated carrier Y the oscillating state for the received carrier r."fiequency, a signal amplifying circuit. a speech amplifying circuit, and switching means `to connect either of said amplifying circuits to the said detector.

In testimony whereof, we have signed our.

namesto thisv specication this 29th day of December, 1923.

CHARLES s. DEMAREST. MrL'roN L. ALMQUIST.