US980359A - Multiplex telephony and telegraphy. - Google Patents

Description

G 0 SQUIER I HULTIPLIBX TELEPHONY AND TELEGRAPHY.

Patented Jan.3,1911r UNITED- STATES GEORGE ownusooiiin; or THE unrrnn STATES ARMY.

ATENT OFFICE.

MULTIP LEX TELEPHONY AND .TELEGRAPHY.

specification of Letters latent.

Patented an. 3, 1911 Application filed November 5, 1910. serial No. 590,804.

(DEDICATED TO THE PUBLIC.)

" ments in Multiplex Telephony and Telegraphy,.of which the following is a specitL- cation;

This application is made under the act of March 3, 1883, chapter 14:3, (U: S. Statute means of wires, .andwhere use is made in this application of the term high frequency,

-XXII, p. 625,) and the invention herein described and claimed. may'bc used by the Government of the United States or any of its ofiicers or employees in the'prosecution 'of work for the United States or by any person in the United States without the payment of any royalty thereon;

This invention relates to multiplex telephony and tele'graphy andhas its object the simultaneous transmission of a plurality of telephonic and telegraphic messages over a single circuit.

A further object of the invention is to makeuse of grounded or eartluzd -.;onnections in combination with the usual metallic eircuit.

A further objectis to render such a system as the above silent to external disturbances and in such manner as to eliminate all cross talk or harmful effects of one nurssage upon another.

A further object is to apply electric waves of such frequencies as to make possible the selection and complete ihdependencc of the various messages.

A further object is to superimpose upon a. standard battery telephone circuit, as now commercially in use, one or more. telephonic and telegraphic circuits .without any inter ference of the various messages.

In accomplishing the above results, use is made of electromagnetic ivaves, or oscillations, of high frequency, propagated by it is understood to mean any ultra-sound .--.frequ'ency"or frequencies above the limit of audition.

Reference is here made to my co-pendin applications, Serial Numbers 590,801 and 590,802, filed November 5, 1910, in which I havediscussed at length the advantages and limitations of the use of electromagnetic waves of various frequencies in such systems as described there and here. In accomplishing the desired results, I heve found it necessary and suflicient tocornbine the engineering practice of wireless telegraphy and telephony with the engineering practice of wire telegraphy and telephony. I have. also found It necessary, in order to obtain satisfactory results, to make use of such detectors as are commonly found in the wireless telegraphic hrt. Attempts have been made at iultiplex telephony, but I have found these inoperative for the reason, among others,

that-no detector or equivalent device has been used. These detectors are not used because of any greater inherent sensitiveness to electrical energy than resides in the telephone receiver itself, but lgcause the energy being in the form of rapid oscillations cannot affect the telephone or other communicating device.- These rapid oscillations can not sensibly affect the telephone, because the diaphragm in its" motion must reverse with the reversal of the current and the deflecting impulse if applied directly to the telephone receiver will be first in one direction and then in the other with a frequency so high that the diaphragm cannot sensibly follow or respond. Furthermore-if the diaphragm should respond with this frequency the efiect would not, be audible. Also in the case of the ordinary telephone, on account of the large self-inductance of the instrument, the high frequency E. M. F. generated by the waves would produce in the telephone receiver only extremely weak currents. I have found it. necessary therefore, and consider it. an important part of my invention. to make use of some form of integrating detector to transform the rapid oscillations into effects p'hich can be manifested by the indicating instrument.

This application iselosely related to my three co-pending applications, Serial Numhers 590,801.590302, and 590.803, filed N0- vember 5 1910. In each of these, use is p made of high frequency waves as :1 vehicle frequency circuits 'in parallel between t e ordinary battery line and the earth.- 'Inthis application I shall describe a manner of conmeeting a plurality of such. high frequency circuits in series relation, making use ofthe telephone circuit and ground connections.

In the drawings forrnin a part of this specification, several modi cations .for c rcuit connectionszare shown, and in said drawings, Figure l illustrates a clrcuit in which a plurality of transmitting or rcceiv-' in .circuits is connected in series in a circult between the ca rth and the ordinary teleph'one line.

modification of I Referring to these figures in detail, Fig.

Figs. 2, 3 and 4: illustrate a 1 shows a common metallic circuit A-A,

'for ordinary tele bony, across which. are' one sets B B. These brid ed the tele g lhde'the usual apparatusin telephone sets-inc resent use in local battery circuits, there ingsho'wn a transmitter 1 of any suitable form'such' as a microphone transmitter with its local battery 2 and the prim ry of the transformer 3. Also there are siown connected in the usual wa the ringing circuit 4, the switchhook 5 an the receiver 6. The secondary of the transformer 3 is bridged directly across the line when the receiver is off the hook.- The invention is not in an way connected with the details of this tele- {16118 connection, an or the usual circuits ing suitable, and t e one described bein given merely as anillustration. Con'necte to the line wire A, at or near its connection to the telephone set B, I have shown a circuit connection to the earth at E, this circuit including the variable inductance I, the secondary coil S, the primary coil. P and the variable condenser C, these .all being connected directly in series. Inductively con-- nected to the secondary S is a primary coil P which is in circuit with the high fr uency generator G, thiscirc'uit also inclu ing a variable condenser C, and a microphone M. Indhctively connected to the primary P; is a secondary coils including in its circuit a variable condenser C and a variable inductance L. Shunted around the condensenis the detector D, and opcratively associated with the detector D is the telephone set F, with a battery if desired. At or near the station 13 is a similar earth -connection, including the inductance I, the primary Pf, the secondary S and the conat the station constructed as to denser C, these being all variable and connected in series in the same manner as shown at the station B. Inductively connected to the rimary P, is a receiver circuit It, simi ar in ever respect to the receiver ll l Inductively connected to the secondary S is a transmitter circuit T, similar in every respect to the transmitter circuit T at the station B. The receiver It is tuned to the frequency of the oscillations given off by the transmitter T and the receiver circuit R is tuned to the frequency developed by the transmitter T, these frequencies being sufiiciently different to afl'ord efl'ective, selective tuning. The tuning elcments throughout the circuitwhich comprise the various condensers and inductances are all variable in order to permit of ready and eilective tuning of each and any circuit. The high frequency transformers are all so 've variable coupling, either by sliding t e one coil within the other, or having one coil swing within the other, or by any other suitable method well known in the wireless art.

The operation of the system is as follows: Ordinary telephonic communications may be carried on between the stat-ions B and B by the telephone sets. Simultaneously therewith high .frequency oscillations may be impressed on the line A'by the transmitter circuits T and T; both of these operating at the same time, if desired. These high fre quency oscillations are modified in'aocordance with speech by the microphone/M, and oscillations transmltted by T are icked up by the receiver R and are rectifie or transformed by the detector D in such-a way as to give a reproduction of speech inathe telephone F, all of these being well known in the art. So also oscillations modified by the microphone M at-the transmitter circuit T will betranslated into speech at the station R. All of these messages may exist on the sameline at the same time without any crosstalk or interference whatsoever. If desired, one ormore'o'f the microphones M may be replaced by suitable tele phic keys in order that communication y'telegraphy'may be carried on. Obviously this change will not affect the principle of the operation in any way whatsoever. The-telegraphic signals may be produced by the ordinary key placed directly in the generator circuit or by such an arrangement as is shown in Fig. 3 of my co-pending-application, Serial Number 590,801. It. is to benotcd in this circuit that I have connected a metallic circuit to .earth at both ends, and I have done this tuning elements, also act as a check to an y earth disturbances in the vicinity. This IS possible only because the condensers- C and C here used are of very small electrical disunensions, being measured in some thousandths ofa niicrofarad, whereas the condensers now in ordinary use in telephone practice have a capacity measured in microfarads. Such large condensers otlcr very small impedance to, the passage of external disturbances of such frequencies as are within the audible limit, but. with my very small condensers and sharp tuning in the ground circuit to a frequency entirely above 0 audition, these low frequency audible disturbances are entirely shut out, giving inc whatchooselo ca ll a silent ground con ncctiou. In view of the fact that heretofore single line telephone circuits which inclutlc a ground return, or a 'QAvirc telephone circuit which is grounded at either end,.arc

subject'to niany and strange noises, the

causes of which are not entirely understood, I consider that in y presentinvention, whereby a I am enabled to use it groundconnection on a single telephone circuitv with no such'disturbances, a 'very important and essential part of my invention. I have found -thc above circuits entirely successful on a standand telephone line circuit COIlSlSlIlIlg of a pair of twisted copper conductors, pa per insulated, which pair constitutes but one out: of a large number -iuclosed in a lead sheath used in ordinary city-- tratfic. This lead sheath surrounding the pair of wires brings the earth connection very close indeed to the line circuit all along its length. but in spite of this. my selective circuits are so effective as to give no trace whatsoever of any crosstall; or influence due -to external disturbances. It is apparentthat any number' of transmitter or receiver circuits may be con nerted in series in addition to the two shown in l-ig. 1. i

Fig. 2 shows a modification of Fig. 1 in which a plurality of earthbrauches are con net-ted in parallel. each single branch connected to earth being similar in every respect tothe earth'branches shown in Fig. 1, and each includingtwo or more circuits which mayi be transmitter or receiver circuits, these circuits being indicated only diagrammatically and designated by the reference characters '1 and R throughout. The

0 connections of the battery sets B and B are shown only diagrammatically. it being nn (lei-stood that the connections are similar to those shown 111 Fig. 1. Each transmitter has a different frequency always being of ultra-sound frequency. and each transmitter has a correspnndn'ig receiver circuit at the (.lher endof the line tuned to its frequency.

590,802, cited above.

of my invention. In connection with Fig. i,

I may also use condensers K and K bridged l across the lines A A which serve the pur pose of placing; the two lines A and A in parallel for the high frequency currents. 'l'his capacity, however, is made so small as to give practically insupcrablc impedance to the telephone currents of ordinary frequencics as given by the telephone sets B and B. It is also obvious. as shown in Fig. 2, that high fret ueney currents may be conuc'rled to the line wire A as shown at T" and R", these circuits having connected in them a plurality of transmitter or receiver" circuits in any suitable arrangement.

Fig. 3 shows a further modification, which is a combination of the systems shown in Figs. 1 and 2- and thesysteuis shown in my c0- pending application. Serial Number 590,802. In this figure, a plurality of branches connected to the earth is shown," each circuit including a plurality of transmitter or receiver circuits, as shown in Fig. 2. I n addition to this highfrequency trans mitter circuits are inductively connected by means .of transformers connected directly in the line circuit in series with the battery sets B and B in the manner described in my covpending application, Serial Number In this case, the corn denser-s K and K are necessaryin order to give a free path for the high frequency as cillations of the series connected transmitter and receiver sets f1" and R.

.Fig. at shows a further modification in which the battery sets B and B and one of the line. wires such as A, are entirely eliminated,in which case I have multiplex telephony by a single wire using earth return. As is-apparent'from this Fig. 4, I have shown a plurality of ground branches, each including a plurality of telephone or re ceiver sets, each transmitter having a different frequency and having a receiver set at the other end of the line tuned to its perio dicity. Also in series with the. line, I have connected other transmitter and receiver sets, as shown diagrammatically at T and R. I In this caseI am able to carry on multiplex telephony by the single wirc'con- -nected to earth at various points without. any cross-talk or disturbances from external causes. and I consider this an essential part- I have shown means whereby Morse tclegraphy. may be. carried on in the. usual way 'nnd-jtliis without any cross interference of the messages. 'In case way stations are used on the line, each of, such stations will be 120 shunted by a small condenser for a -,con denser and inductance tuned to the frequency of the highfrequncy oscillations. Thus it is apparent: that my invention may be supcl'ii'i'iposed directly on the"prescnt" Morse telegraph systems. Other forms of.

high frequency transmitter and rcceiver cir-- cuits may be used in place of those shown,

and various suitable modifications are shown' limited to the exact connections shown, but

What I claim as my invention is the following:

1. In a silent earthed multiplex telephone and telegraph systei'n, a l ne wire; a plurality of earth circuits extending from said line; a plurality of transmitter or receiver circuits associated in series relation breach of said earth circuits, each transmitter 011" cuit impressing different but ultra-sound frequencies on the line, each receiver circuit being tuned to the frequency of one transmitter. i i

2. In a silent earthed multiplex telephone and-telegraph system, a line wire a plurality of earth circuits extending from said line; a plurality of transmitter or receiver circuits associated. in series relation in each of said earth circuits, a plurality of transmitter and receiver circuits associated in series in the line, each transmitter impressing different but ultra-sound frequencies on the line, and each receiver being tuned to the frequency of one of the transmitters.

3. In a multiplex telephone and telegraph system, a line wire; low frequency signaling apparatus connected to the line, a plurality of round circuits extending from said line, a p urality of transmitter or receiver circuits associated in series relation in each earth connection, each transmitter circuit impressing different but ultra-sound frequencies on the line, each receiver circuit being tuned to the frequency of one transmitter.

4.,In a multiplex telephone and telegraph system, a pair of line wires; low frequency signaling apparatus associated therewith; a plurality of: earth connections placed between each line and-the earth, a plurality of high frequency signaling circuits associated inseries'in each earth connection, each transmitter circuit developing oscillations of different but-ultra-sound frequency and each receiver tuned to one transmitter circuit.

5. In a multiplex telephone and telegraph system, a pair of line wires; low frequency signaling apparatus bridged across said lines; a plurality of earth connections placed between each line and the earth, a plurality of high fretfiiency signaling circuits asso' ciated in series in each earth connectiom'cach transmitter circuit. developing oscillations of ceiver circuit being tuned to one transmitter circuit and containing a detector for high 55 frequency oscillations and a telephone rcceivcr operatively associated with said do tcetor.

6. In a multiplex telephone and telegraph system, a pair of line wires, battery tccphone sets bridged across said line wires, a plurality of earth connections )laced between each line and the earth, a p urality of high frequency signaling circuits associated in series in each earth connection, each trans-t mit-ter circuit developing oscillations of different frequency, each receiver circuit being tuned to one transmitter circuit and contain ing a detector for high frequency oscilla- -tions and a telephone receiver operatively associated with said detector.

7. In a multiplex telephone and telegra h' system, a pair of line wires, battery to e-- phone sets bridged across said line wires, a-

plurality of earth connections placed be- 2 tween each line and the earth and containing a variable condenser and a variable inductance, a plurality of high frequency signaling circuits inductively associated in series in each connection, each transmitter circuit containing a generator of high frequency oscillations, a variable condenser and mike-- tance for tuning said circuits and a telephone transmitter for modifying said oscillations,

each receiver circuit being tuned to' one of the transmitter circuits and containing a detector of high frequency oscillations and a telephone operatively connected therewith.

8. In a multiplex telephone and telegraph system, a pair of line wires; battery telcphone sets bridged across said 'line wires; a plurality of earth connections placed between each line and earth and containing a variable inductance, and variable condenser;

a plurality of high frequency signaling cir.-

cults inductively associated in series in each earth connection a plurality of signaling circuits connected inductively in series in the lines, each transmitter circuit developing oscillations of different p ltra-sound frequencies and containing a microphone transmitter for modifying. the"oscillations in accordance with speEch,--each receiver circuit coiiltaining a variable inductanceand a variable capacity,

and tuned to thefrequency of one transmitter circuit, a detector in shunt to, thecondenscr of the receiver circuit and a telephone operatively connected therewith. Y

9. lira multiplex telephone and telegraph system, a. pair of line wires; battery tele p'hone sets bridged across said line wires;

a condenser small capacity parallel to each of the battery telephone sets; a plurahty of earth connections placed between eachline and earth and containinga vent-" difi'eieiitbut ultra-sound frequency, each re able iriductance. and a variable 'capacity, 'a

plurality of high frequency signaling cit" containing a variable inductance and a vari- 1Q cnits inductively zifitiQCiillQLi in'scries in each able capacity and' tuned to the frequency of -(IXI'lll connection; :1 plurality of signaling one transmitter circuit, a detector in shuntcircuits connected inductively in series in the 3 to the condenser 0f the receiver circuit and 55 lines, each transmitter circuit developing a telephone operatively connected therewith.

electric waves of Llill'ei'ent ultra-sound fre- GEORGE OWEN SQUIER. quencies and containing a nnerephune Lrans- \Vitnesses: lnitter for modifying the oscillations in ac- P. I. VVOLD,

cordance with speech; each receiver circuit R. CRAM.

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