US1556311A - Signaling system - Google Patents

Description

oct. s, 1925. 1,556,311

J.DAWDSON,JR l

SIGNALING SYSTEM Filed Dec. 2?:I 1920 Patented Oct. 6, 1925.

1 UNITED ,STATES y 1,556,311 :PATENT OFFICE.

JOHN DAVIDSON, JR., oF TRENTON, NEW JERSEY, yAssIcrNoR TO AMERICAN 4"TELE- 4 PHONE AND TELEGRAPH COMPANY, A CORPORATION OF NEW YORK.

sIGNALINe sYs'IInu.`

Application niedvnecember 23, 19:50.y seriai No. 432,783.

To all whom-#May concern.' Beit known that'I, J oHN DAvIDsoN, Jr.,

residing at Trenton, in the county of Mercer and State ofNew Jersey, have invented certain Improvements in a Signaling System, of which the following is a specification. n v vThis invention relates to signaling systems and particularly to an arrangement whereby the signaling apparatus associated lwith a telephone circuitmay be -controlled .by means of a modulatedhigh frequency current.

It has been customary heretofore to operate the signaling apparatus associated with telephone circuits by lmeans of currents of relatively Alow frequencies, lthat isto say, currents varying from approximately 16 to 133 cycles vper second. With the development of long distance telephony and teleg-l raphy, especially through the invention of vthe so-called carrier systems, it'vhas been found that the signaling-frequencies `heretofore used could well be used for revenue producing purposes, as for instance for alternating current telegraph. The voice frequency range (which is not, available for additional revenue producing channels) was thereforey proposed for .signaling since talking and signaling are notdone-at vthe same p time. It has accordingly been foundy desirable to use signaling currentsof higher frequencies'so asv to take them voutside the frange of frequencies of the proposed telegraph channels butat the Sametime to keep the frequency of the telephone signaling current ywithin ycertain prescribed limits.

It is they object of this invention to provide an arrangement whereby a modulated `high frequency signaling current may be impressed upon the line circuit andtransmitted thereover as such high frequency Ycurrent and'to vdemodulate the said high frequency current'using its low frequency component for the operation of the terminal signaling apparatus.

1 Other and further ob'ects of this invention will be apparent rom the following description when read in connection with lator.) 3 andfl its which may be of any well-known type. Bridged `across the terminating end of the line circuit L1 is a relay R.1 which is adapted to respond to low frequency ringing current impressed thereon by the operation of the relay R2 and tol cause thereby the operation of the relay R3 which, in turn, vlights the line signal l. Another relay R,v associated with thesleeve of the ack J 1 is adapted to f' lopen the .circuit of the relay R1 and also to extinguish the line signal lamp l Vwhen the plug-PL is insertedin jack 1. "Also, by .the act of inserting a plug in said jack, the f l relay `R5 Lis operatedwhich, in t'urn, roperates relay R6 whereby filaments of the vacuum tubes associated with the oscillator 2 and the modulator 3 are heated thereby setting in operation the said oscillator, and putting the modulator in condition to function properly. The operation of relay R, alsor conu y nects with .the modulator circuit a source of v135 cycle current whereby the unmodulated oscillations, for example, V2000 cycles set up Vby the said oscillatorr 2, may be modulated.

Bridged across the -lineV circuit L1 at Athe points 4, 4Lk is aV relaynR7 which, by means of vind'uctance 5 and capacity 6, is lmade responsive tothe low Vfrequency current impressed upon the line circuit bythe operator whenever thev ringing key of the cord circuit associated with the plugP1 is operated but is not responsive to highv frequency oscillations received over the linev Ll from a distant point. The` operation of relay lR7 grounds thevvwinding of relay Rs which causesthe operation fof relay R, and im- .pr'esses-upon-the line circuit L,.the modul.lated lhigh frequency oscillations which, as

previously stated, wererset up bythe moduwhich, for example, represents a band resulting from the modulation of the 2000 cycle current with 13,5 cycle current. These high frequency oscillations are impressed upon the detector 10 and the resulting low freq'uency `current will cause the operation of a sensitive relay R9 which,'in turn, releases the' normally operated, slow-release relay Rw. This slow-releaserelay in turn controls they operation of the relay R2 which;

associated apparatus. Bridged across the line circuit L1v at the. Ipoints7, 7 is a circuit`8'which i'sjcoupled with-the input circuit 9 of a vacuum tube ldetector 10; VThe circuits 8 and 9 `are tuned for the reception of the modulated frequency effects the application of the low frequency current., of, for example, approximately 20 cycles, to the relay R1 which isy bridged across the switchboard end of the line L1;

Having in mind the foregoing description of the parts comprising the arrangement shown in Fig. 1 in which this invention re'- sides, the nature of the invention will be more clearly understood from thefollowing description of the mode of operation of this 'arrangement Let it be'assumed that the operator at A desires to signal the operator at the vdistant end of the line Lrpand1 thaty the apparatus connected 'with the distant end of this line isv substantially that shown in thefigure. llien the operator `ai; A inserts the plug P1 in the jack J1 land depresses the ringing' key of the cord circuit associated with vtheplug P1, low frequency ringing current will be impressed 'across the line L1. This results in the operation of relay R7', since the impedance. of the path through this relay is ylow for current of this frequency. Relay R7 will be operated thereby operating relay R8 and the armatures of the latter relay will connect theli'ne side of line L1 with the contact-s withv which the source of modulated high frequency signaling current is connected. Furthermore, when the plug P1 is inserted in'jacll Jrelay R4 will be operated, thereby removing the bridged relay R1 from the line, and also relay R5 will be operated which, in turn, causes the operation of relay R6. When relay R6 is operated current will flow from battery B1 ythroughthe filamentsof the oscillator 2 and the modulator 3 and at the same timethrough the closing of the outer contact of relayR6 135 cycle current will be impressed upon the circuit of the modulator by means ofv a vtransformer The oscillator '2 may be of any wellknown type or arrangement and as is well known, such circuits' will begin to oscillate as soon asthe filament of the vacuum tube connected therewith is heated. Accordingly the unmodulated oscillations from the oscillator circuit 2 will vbe modulated by the 135 cycle current which is also impressed upon the input side of the. modulator 3 andy the resulting modulated oscillations willbe impressedup'on 'the line circuit connected with the'inner contacts of relay R8. The resultantV modulated vhigh frequency oscillations will be impressed upon'the line L1 andV in turn will be impressed upon a circuitat the distant end of the said line circuit similar to the circuit shown in the figure.

The action of these high frequency oscillations at the distant end will be thesame as would-take place if similar modulated high frequencyk oscillations were impressed 'upon the distant end and were received by the terminal circuit shown in the figure.

Let it be assumed that such modulated high frequency oscillations have been impressed upon the line L1 at thedistant end and that the plug P1 of the cord circuit at A has not been inserted in jack J '1. rllie modulated high frequency oscillations will be impressed upon the circuit 8 and those oscillations falling within the frequency range of the tuned circuit 9 will be impressed thereon and in turn will be detected by means of the detector 10. The 135 cycle component of VYthe high frequency `wave, which appears in the output side of detector 10 will energize relay R9 which will open the circuit of relay R15 allowing this armature to drop back. This act results in' the grounding of a winding of relay R21 connected withthe line circuit L1 and'ZO cycle ringing current will be in'ipressedupon the relay R-l which is bridged' across the tip and ring side of the switchboard end of the line L1. The relay R3 will 'accordingly be operated, locking up'over Va contactof relay R4L and also lighting the line signal lamp 1.

When the operator at A takes up the'call by inserting the plug P.1 in' the jack J1, current fromthe battery B, of the sleeve of the plug will operate relays and' R5. 'The operation of relay R4 results in extinguishing the light of the lamp 1 and also opening the circuit of the bridged relay R1. The operation of relay R5 results in settingin operation the oscillator and causing'thereby the production /of modulated oscillations, but in view of the fact that relay R7 remains inoperative, relay RS will accordingly remain inoperative and the highV frequency oscillations from the output side of the modulator 3 will not 'be impressed upon the line L1.

It will be seen that my invention comprises an arrangement for ringing over telephone circuits by means of modulated high frequency oscillations which are transmitted from one end and detected or demodulated at the other end of the circuit and' using the low frequency component for theoperation of a sensitive; relay which in turn applies lowfrequency current for the operationof the signals in the 4manner which is well understood. Y i

In the form in which this invention has been disclosed in Fig. 1 not only is the unmodulated lcarrier frequency transmitted but also both of the side bands arising from the superpositionfthereon of the 135 cycle modulating current. However, by the insertion lin the circuit between the modulator and the relay 4RS of suitable filters of any well known type as shown in Fig. 1a, only one side blandfmay be transmitted which may be detectedI by means of a suitable tuned circuit connected with the circuit of the detector 10.v KBy adjusting the lilters, which may be of the band type, yboth the carrier and one band may be transmitted.

Although this invention has been disclosed as embodied in a particular form for arrangement of parts, it is to be understood it is capable of embodiment in other and different forms without departing from the spirit and scope of the appended claims.

What is claimed is:

1. In a signaling system the combination of a line circuit, `a cord circuit having a source of ringing current connected thereto, a source of high frequency oscillations, a source of low frequency variations, means to modulate said high frequency oscillations by the said low frequency variations, and means controlled by the connection of the said cord circuit with the said line circuit to effect the modulation of the said high frequency oscillations by the said low frequency variations.

2. In a signaling system the combination of a line circuit, a cord circuit having a source of ringing current connected thereto, a source of high frequency oscillations, a source of low frequency variations, means to modulate said high frequency oscillations by the said low frequency variations, and means controlled by the application of the low frequency ringing current to the said line circuit to cause the said modulated high frequency'oscillations to be impressed upon the said circuit.

3. In a signaling system the combination of a line circuit, a cord circuit adapted for connection with the said line circuit and having a source of low frequency ringing current associated therewith, a source of modulated .high frequency oscillations, and means responsive to the application of low frequency ringing current to the said line to control the Connection of the said source vof modulated high frequency oscillations to the said line circuit.

4. In a signaling circuit characterized by the transmission thereover of modulated high frequency waves, the combination with a line circuit of a line relay and signal associated therewith, a detector adapted to ldemodulate the said waves, a second relay trolled by the said cord circuit to impress the said high frequency oscillations uponl the said line circuit, a detector circuit adapted to have impressed thereon high frequency oscillations received over the said line circuit from its opposite end, andmeans connected with the output side of the said detector circuit for controlling the operation of the line signal connected with the said line circuit. r

6. In a signaling system the method for operating the line relay associated with long telephone circuits which consists in generating high frequency oscillations, modulating the said high frequency oscillations with low frequency variations, impressing the said modulated oscillations upon the line circuit,

receiving the said modulated oscillations at the opposite end of the line circuit by a detector circuit tuned to reception frequency, and impressing the detected low frequency component upon a relay adapted to control the operation of the line signal by means of low frequency current.

7 In a signaling circuit, the combination with a line circuit of a terminal circuit having a link circuit associated therewith, the said terminal circuit comprising means for generating a modulated high frequency wave, means for receiving and detecting a modulated high frequency wave, and means controlled by the connection of the said link circuit to the said terminal circuit to disconnect the said receiving and' detecting means from the said line circuit when the said generating means is connected therewith.

8. In a communication system comprising a low frequency communication circuit adapted to be connected with a carrier frequency transmission circuit, the said carrier requency circuit having means associated therewith for generating a carrier frequency current modulated by an intermediate frequency signaling current, the method of signalin which consists in connecting the said low requency communication circuit with the said transmission circuit controlling thereby the generation of the high frequency carrier current and its modulation by the intermediate frequency current, and applying low frequency signaling current from the said low frequency circuit to the Vhigh frequency circuit to control the application of the modulated carrier current to the said high frequency transmission circuit.

In testimony whereof, I have signed'my name to this specification this 21st day of December 1920. s

JOHN DAVIDSON, JR.

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