US1617391A - Carrier-transmission system - Google Patents

Description

. 1,617,391 J. s. JAMMER CARRIER TRANSMISSION SYSTEM Filed April 9, 1923 RBF.

5 LPF cs t m 3 o v Q l I CARRIER i 8 FREQUENCY [L l o i Q I 5 I g: MODULATING g 5 11.! IYIFREQVEMCIESV' I ND I I I I BAND I 1 Li.

FREQUENCY I mike/770K? Jacob J Jammer Patented Feb. 15, i927.

"raranrerrics.

JACOB s. JAMMER, ornnw YORK; N. Y., P NY; moonronatrnn, 013 new YORK,

MTEQ stereos" Assrcn'on T wns'riinn ELECTRIC COIVI- N. Y., A'CORPORATION OF NEW YORK.

oAnnIEn-TR NsM rssIoN sYsT'iiM, r

n Application filed April,

This invention. relates; to carrier transmission systems, and more particularly to carrier telephone systems. I w

An object of the inrention is to supply to a plurality of carrier current transmitting channels carrier oscillations ofthe same fre-,

quency from the same f source without interchannel modulation or cross-talk.

Anotherlobject .is to prevent interchannel interference between transmitting channels of a carrier telephone system wherein acom- Inon source. supplies to all channels carrier waves of the same frequency. I y In accordance w th .tlllS invention the transmitting channels of a plurality of single channel carrier systems supplied'with carrier waves of: the same frequency from a r nels.

common source are connected to said source by frequency discriminating means tuned to the carrier frequency whereby the currents in one channel due to modulation are con:

fined to said channel andtherefor'e do not interfere with theoperation of other chan- The inventionwill be described as applied to a plurality of singlechannel carrier telephone systemsfalthough it will be understood that it is also applicabletoa plurality of multiplex carrier systems wherein one channel of, each of the several systems is supplied with carrier Waves o-f'the same frequency from a common source.

While the invention is llustrated as applied to carrier transmission systems wherein the .unmodulated I carrier components are transmitted from the'sending to the receiving terminals, together with the side .hands representing signals it will be evident, of

course, thatit is also applicable to systems operating upon the principle of suppression of the uninodulatedcarrier frequency coin-' ponent.

In the drawing:

Fig. 1 illustrates diagrammatically only so much of a plurality of single channel care I rier telephone systems as isnecessary for an li s-a, 's, ea we whi h W. ree we understanding of the invention. r Fig.2 is a curve indicating the efficiency ,of the frequency discriminating means connecting the transmitting channels to the common carrier source. I v.

y The :apparatus and circu ts illustrated in Fig..- are located at theijunctions be 1923; serial No; 630,728.

oscillations are to be transmitted and received and correspondinglines ML ML etc, I over which modulated: high frequency oscillationsare to be transmitted and received.

While for the purpose illustration only two sets of coupled low" and high frequency lines are shown, it will be understood many more may be, and in practice usually will be,

provided. 7

The illustrated sets offcoupledlow and high frequency lines and the coupling appa ratus and circuits therefor are exactly alike so a description of one will sufiice. I

ceiving channels TL and R-L are associated with the 10w frequencyv line L through transformer 1..

j Thetw o'channelsTL and BL are rendered'substantially conjugat'eby the provision of an artificial line or ance the line'L l H The transmitting I and receiving channels iet AL tobalQ The high frequency transmitting and rev TL and' RLi, respectively. are connected to t V i the high frequency lineML through transmitting and receiving band filters TBF, and REF which "separate the outgoing and incoming oscillations. -.Carrier oscillae trons of one frequency! are employed for transmission in one"direction and v carrier oscillations of another frequency are employed for transmission in the opposite direction.

These band filters are of the general'type v disclosed. inU. 'S. patents to George A Campbell Nos. 1,227,113 and,1.227,11& date-:5

May 22, 1917 The transmitting .band'filter 'IBF designed. to pass currentsof'flthe transmitted carrier frequency and of fife ii n the upp r at-1 W side band and to suppress currents of allwithin either the upper or lower side band and. to suppress currents of all other. frequencies.

The main line ML may, of course, be-utilized for the transmission of audio or lower frequency oscillations, high pass and low passrfilters HPF, and LPF being provided, as shown, to separate the audio and ultra audio frequency oscillations. v

The transmitting channel TL includes a modulator M and the transmitting band filter TBF previously referred to, the output of the former being connected to the latter by a transformer 2.

The modulator M may. be of any well known type, but, as illustrated, is of the three element space current type.

Carrier oscillations of the frequency as signed for outgoing transmission are supplied to the modulator M, from. a source CS common to all of the illustrated transmitting channels.

The'low frequency modulating currents from the low frequency line L, delivered by the transformer 1 are impressed upon the input circuit of the modulator M, through a transformer 3.

The incoming or receiving channel RL includes the receiving band filter REF a demodulator DM and a low pass filter LPF. The demodulator DM may be of' any well known type, but, as illustrated, is a three element relay of the space current type. The amplitude of the received currents impressed upon the demodulator DM is regulated by a potentiometer 4. e

v The low pass filter LPF which is of the general .type disclosed in U. S. patents to George A. Campbell- Nos. 1,227,113 and 1,227,114, isdesigned to passonly currents of the original modulatingfrequencies and to suppress currents of all other frequencies.

As previously stated, the source CS supplies to each modulator of the several illustrated transmitting channelscarrier oscillations ofthe same frequency.

Since the input circuits of the several modulators are connected in multiple relatalk.

For such purpose, the carrier supply leads 5 are inductively coupled to each modulator input circuit by a transformer 6, the primary of which is tuned to the carrier fre-' quency currents by'an inductance 7 and condenser 8 cooperating with suchprimary, and the secondary of which forms, with variable condenser 9, a loop circuit tuned to the car rier'frequency. v I

This tuned inductive coupling is highly efiicient for the transmission ofcurrents of carrier frequency to which it. is. tuned;.-but isso ineflicien't for the transmission of currents of the modulating frequencies 1111- pressed'upon the input circuit through transformer 3 as to prevent the passage of such modulating currents to the carrier supply leads 5.

Currents of both the carrier frequency and the modulating frequencies are present in the input circuit ofthe modula'torlvl and some modulation of the carrier currents occurs in the input circuit Therefore there are also present in the input circuit currents of frequencies within both the upper and lower side bands of the carrier wave.

If such currents of frequencies within either the; upper or lower side band are impressed upon the carrier supply leads 5, they will pass into the input circuits of the modulators of the other transmitting channels and thereby cause cross-talk between with carrier currents of the same frequency from the same source are prevented;

F 1g. 2 is an efiiclency curve of the frequency discriminating circuitswhich couple the transmitting channels to the carrier current supply leads 5. i In this figure, frequencies are plotted against efficiency of'transmission of currents of the frequencies represented.

Inspection of this eth'ciencycurve shows clearly that the frequency discrin'iinating circuits are highly efficient for the transmission of currents of carrier f:.:equcncy and are very inefficient for the transmission of currents of all other frequencies.

The amplitude of the carrier currents supplied to the input circuits of the modulators is regulated by potentiometers 10.

The invention set forth herein is, of course, susceptible of various other embodiments and adaptations. I

What is claimed is:

1. In a carrier transmission system, the

combination of a plurality of modulators each included in a separate transmitting channel, a source of carrier currents from which carrier currents of the same. frequency are supplied to each modulator, means to supply modulating currents of audio fre- ,quency to each modulator, and means comprising a circuit tuned to'currents of carrier llll frequency connected in the input, circuit of each modulator and in circuit with said source.

2. In a carrier transmlssion system, the

' coinbination'of a source of carrier oscillasame frequency to the modulator of each channel, means to supply modulating currents ft lower frequency to each modulator,

and means comprising a circuit sharply tuned to currents of carrier frequency connected between said source and each modulator.

3. In a-.carrier transmission system, the combination of a plurality of modulators, each in a separate transmitting channel, a source of carrier currents from which carrier currents of the same frequency are supplied to each modulator, means to supply modulating voice frequency currents to each modulator, and means to connect said source to the input circuit of each modulator comprising a series circuit and a loop circuit inductively coupled and sharply tuned to currents of the carrier frequency. g

4. A carrier transmission system comprising a plurality of transmitting channels, a source of carrier currents from which carrier currents of the same frequency are supplied to each channel, means associated with each channel to modulate in accordance with signals the carrier current supplied thereto, and means'to prevent lnterchannel modula- 7 tion comprising for each channel an inductive coupling between'the' source and said modulating means, said couplings being tuned to currents of the carrler frequency.

5. In a carrier transmission system, the

combination of a plurality of modulators,

each included in a separate transmitting channel, a source of carrier currents from which carrier currents of the same fre ing circuits tunedto currents of the carrier frequency connecting the modulators to said source.

l, 7. A plurality of transmitting circuits, a

common source of oscillation of a single frequency for supplying signaling energy to each of said transmitting circuits, and means very sharply selective of oscillations of said single frequency connecting each of said circuits to said source. i j

v 8. lhe combination of a plurality of modulators each having an input circuit and each included in separate transmitting channels adapted for simultaneous and independent operation, separate sources of modulating currents connected to said input circuits, a source of carrier waves, a common common supply circuit and each of said modulator input circuits.

9. A. plurality of transmission lines adapted for simultaneous'and independent operation, a modulator associated with each of said lines, a source of carrier waves, a common supply circuit connecting said source 7,

of carrier waves to the input circuits of said fmodulators, whereby carrier currents of the same frequency are supplied to each modulator, means to supply modulating currents. of audio, frequency to the input of each modulator, and frequency discriminating means tuned to the carrier frequency connectedbetween sa1d common supply c1rcu1t and each of sa1d modulator input circuits,

whereby the modulating and modulated 'currents in each of said modulator input circuits are prevented from entering the other modulator lnput eircults.

.10. In a carrier transmission system, the

combination of a plurality of modulators each having an input clrcuit and each 1ncluded in separate transmitting channels.

adapted for simultaneous and independent operation, separate low frequencylines 0011-.

nected to each of said modulator input circuits to supply currents of audio frequency thereto, a source of carrier currents, a coma men supply circuit connecting said source of In witness whereof, I hereunto subscribe. day of April, A. D., 1923;"

my name this 2d JACOB S. JAMMER.

Images