US1463200A - Ringing arrangement for multiplex circuits - Google Patents

Description

.July 91; 1923. 1,499,299

J. DAVIDSON, JR

RINGING ARRANGEMENT FOR MULTIPLEX CIRCUITS Filed sept. 24, 1919 2 Sheena-sheetv 1 IN VEN TOR.

lull v Bfavb'dSO/@Jm ATTORNEY Jlyl, 1923. 1,463,200

J. DAVIDSON, JR

RINGING ARRANGEMENT FOR MULTIPLEX CIRCUITS Filed'sept. 24, 1919 2 sheets-sheet 2 IN VEN TOR.

ATTORNEY k Patented July 31, 1923.

UNITED STA-,Tas

1,463,200 PATENT oFFIcE.

J'OHN-NAVIDSON, 'I'B,.,.VOFl HONTCLAIR, NEW JERSEY, ASSIGNOB TO AMERICAN TELE- PHONE AND TELEGBAPH COMPANY, A CORPORATION F NEW YORK.

'BINGING @RANGEMENT Fon mULTTrLEx CIRCUITS.

Application illed September 24, 1919. Serial No. 325,824.

To all whlom it may concern.'

Be it known that I, JOHN DAVIDSON, Jr., residing at Montclair, in the county of Essex and Statev of New Jersey, have invented certain Improvements in Ringin Arrangements for Multiplex Circuits, o l'which the following is a specification.

. This invention relates to multiplex systems employing'carrier currents and more particularly to arrangements whereby ringing-orother signaling currents may be transmitted o ver the channels of such a system.

. Oneof the features of this invention resides in the provision in a carrier system of 'a special amplifier 4for amplifying ringing currents -received from the carrier transmission 'circuit, so 'that the ampllfcation of said ringing currents may be adjusted to any desired degree independent of the amplification desired for telephonie or other signaling currents.

v Another feature of the invention resides in the provision of an arran ement in the low frequency line or circuit or controlling thel relaying' of ringing currents in either direction at the junction -point of the low fre- I quency line or circuit with the carrier sys- These' features, together with other features of the' invention, which will more fully appear-hereinafter, may be realized in accordancewith the detailed arrangement set forth in the following description and illustrated in the accompanying drawing, Figures 1 4and 2 of which constitute circuit diagrams of two embodiments of the invention .and Figure 3 .of which illustrates a'circuit arrangement of a form of oscillator which maybe. employed for supplying ringing curren In 'Fi re 1 ML designates a main line or circuit, or the transmission of carrier currents. Common transmitting and receiving circuits TL and RL are associated with the mainline ML through a balanced transformer 10. In order that the circuits TL 'and RL ,may be rendered conjugate so that electrical. disturbances in the one will be 1vivithouteect upon the other, the main line is balanced -worh L designates a low uency signaling line or circuit, which, in common with a plurality of other lines, is adapted to transmit signals over the mainf line 11H1. 111 .the

`by an artificial line or net-' case illustrated, the line L, vis an ordinary low frequency telephone circuit. The line L, is associated through the transformer 11, with an outgoing carrier transmission channel TL, and an incoming carrier receiving channel 'RLP These two channels are rendered substantially conjugate by roviding an artificial line or network N, for balancing the line L,. The channels TL, and RL, are

associated with the'fcommon circuits .TL and RL through filters TF', and RF, respectively. Similar channels corresponding to other low frequency signaling clrcuits ma be associated with the circuits TL and RL the carrier frequency assi ned.to the channel, the bands being of su cient width to accommodate the frequency variation due to the modulation of the basic carrier'ffrequency by the si naling frequencies; The

bands transmitte by the filters-TF', and

RF, may in practice be the same. The bands transmitted b l other filters, such as' TF', and RF,"v shou be sufficiently remote from the bands transmitted by the filters TF', and RF, to` allow, for frequency separation 1 ltween the channels.

The transmitting channel TL, includes a modulator M a band filter TF and an amplifier TA,. The modulator any-well-known type, but is illustrated 'as a duplex vacuum tube modulator of the ty illustrated and described in the U. S. app 1- cation ofJohnR. Carson, Serial No. '157 ,413,

filed March 25, 1917. The modulator is suplvf, may be of` of the broad plied with carrier currents of the frequency assigned to the channel, over a circuit 12. Thearrangement is such that carrier curl rentsare not transmitted by the' modulator unless the circuit is unbalanced, due to the ap lication of signaling current thereto.

he filter TF, is a band filter of the type disclosed in the Campbell patents above referred to and is desied to suppress low frequencies and ass t e carrier frequencies. 'llvhc amlifier A, may loe of any1 4well- 'own taracter, but is preferably a duplex aan vacuum tube amplifier, which, as is welllmown, provides a minimum degree of. distortion at high frequencies and hence is lli well adapted for the amplification of carrier currents.

The receiving orincoming channel RL, includes a detector or demodulator D,. This demodulator may be of any Well-known type, but is preferably a duplex vacuum tube modulator of the general character illustrated and described in the U. S. application of John R. Carson, Serial No. 157,- 414, filed March 26, 1917. The duplex demodulator described in the said Carson application operates upon the so-called homodyne method of receiving and consequently is supplied from the circuit 13 with oscillations of the carrier frequency assigned to the channel. The oscillations supplied from the'circuit 13 react in a well-known manner with the received modulated currents, to detect the low frequency signaling currents.

The channel RL, also includes an amplifier RA, and a filter RFQ. The amplifier ltA, is preferably a vacuum tube amplifier as illustrated, and serves to amplify the detected signaling currents. The filter RTF', may be of the general type illustrated in the above mentioned patents to George A. Campbell and is preferably so designed as to transmit a range of frequencies extending from Zero up to the highest frequency emplo ed in ordinary telephonie transmission.v

ince it is generally customary to ring over lines such as L, at relatively low frequencies, such for instance as 16 cycles per second, it is desirable that some apparatus should be provided at the junction between the lowQfrequenoy line and the carrier system, to translate these ringing currents into ringing currents of some higher frequency which is more suitable for the modulation of carrier currents. lt has generally 'been found that ringing currents having a frequency of 133 cycles is adapted to this purpose, although it'will be understood that other frequencies may be used, if preferred. lin order to produce the translation in ringing frequency above referred to, the line L, isA provided with.v a ringing responsive relay 1li associated with the left hand winding of a transformer 15. Said relay 14 controls aV relay 16, whereby ringing current from a source RS may be applied to the junction point of the line L, with the transformer 11, so that ringing current is transmitted through said transformer to the outgoing carrier channel TL,. The 133 cycle 4.ringing source RS may be of any wellknown character, but is preferably an oscillating vacuum vtube arrangement such as' illustrated in Figure 3. Form-reasons of economy it is desirable that this ringing source should supply ringing current for a c incarico plurality of signaling circuits and consequently its outgoing circuit 17. is provided with parallel connections leading to the contacts of relays such as 16 for a number of diderent circuits.

ln order to provide for relaying ringDing currents incoming from the main line dL to the line L, a circuit 18 leading to the input of an amplifier A, is connected to the right hand winding of the transformer 15. The circuit 18 is turned by means of the condenser to respond to 133 cycles. A ringing responsive relay 19 is associated with the output circuit of the amplifier A, and controls the circuit of a relay 20 which applies 16 cycle ringing current to the line L, over its front contacts and simultaneously short circuits the outgoing channel TL, in order to prevent the transmission thereto of 133 cycle ringing currentv incoming from the channel RL,. TheI relay 19 controls the relay 2O through a slow acting relay 21 which, when it functions to close the circuit of the relay 20, simultaneously opens the circuit of the relay 16 to prevent a false operation of said relay. The relay 16 is also so arranged that when actuated to apply ringing current to the channel TL, it prevents the de-energization of the slow acting relay 21, so that it is impossible to complete a circuit over the relay 20.

The operation of the arrangement of lF igure 1 is as follows: Talking currents incoming from the line L, are transmitted through the transformer 11 to the circuit TL, and are impressed upon the modulator M,. High frequency carrier currents from the circuit 12 are now modulated by the modulator M, in accordance with the talliing currents and the modulated high frequency currents are transmitted through the filter Tll` amplified by the vamplifier TA, and then transmitted through the lter TF, to the common circuit TL. These -modulated carrier frequencies, together with modulated carrier frequencies from other channels simultaneously impressed upon the circuit TL, are transmitted throu h the transformer 10 tothe main line ML. Vlodulated carrier currents incoming from the y line ML, having the ro er frequency, are selected by the filter from the circuit RL and impressed upon the detector D? As a result of the reaction of the received carrier currents and the unmodulated carrier currents from the circuit 13 in the detector l) the low frequency talking currents appear in the output circuit of said detector, and are impressed upon the amplifier RA,. After being amplified the low frequency currents are transmitted through the filter lill', to the main line L,.

Sixteen cycle ringing current incoming from the line L, actuates the ringing responsive relay 1d which at its lower front contact completes the circuit froml ground over thenormally closed contact of relay 21,

front contact of relay 14 and throughthe winding of relay 16 to battery. Relay 16, at its front contacts connects 133 cycle ringing current to the right Winding of the transformer 11 and said ringing current is transmitted through the transformer 11 to the outgoing carrier channel TL1. The relay 16 at its lower front contact also connects ground to the Windingv of the slow acting I' relay 21, thereby preventing thev said slow acting rela from being cle-energized, due to the chattering of the contacts of the ringing responsive relay 19:' Relay 21 is therefore held actuated and prevents vfalse operation -of the relay 20. The 133 cycle ringingcurrent transmitted to the channel TL1 is limpressed upon rthe input of the modulator M1 and modulates carrier current from the circuit 12. The modulatedgoarrier vcurrent is then transmitted through the filter TF1, amplified byl lthe amplifier TA1 and passed through the filter TF 1 to the common circuit TL, from which it is transmitted through the transformer 10 to the main line ML.

Carrier currents modulated in accordance with rin ing currents `and transmitted over the line froma distant station, are impressed -upon the common circuit RL and are selected through the filter RF1 and impressed upon the -input circuitA of the vde-l niodulator D1. The modulated carrierfrequencies react with carrier currents from the circuit 13, so that 133 cycle ringing cur'- rents appear in the output circuit of the demodulator D1. These 133 cycle ringing currents are amplified lby the amplifier BA1 and transmitted through thefilter RF1 and over the contacts of the relay 16 to the circuit 18. From the circuit 18' the 133 cycle ringing currents are assed tothe amplifier A1 which amplifies t e ringing currents so that the amplified currents actuate the ringing responsive relay 19. The actuation of this relay causes the de-energization ofthe slow acting relay 21 which disconnects ground from -the circuit of the relay 16' to prevent a false operation and connects ground to thel circuit of relay 20. Relay 20 is therefore energized and applies 16 cycle ringing currents over its front contacts to the -line L1. At the same time it short circuits the channel TL1 at its upper front contact to prevent the transmission of 133 cycle ringing current from the circuit RL1 to the circuit TL1.

In the arrangement which is described it will be noted that the means for relaying the ringing currents in both directions is associated with -the low frequency line L1. A modification of the invention is illustrated 'in Figure 2, in which the 133 cycle ringing current is applied to and taken o from the carrier channels. In this figure a relay 22 responsive to 16 cycle ringing current is bridged across the line L1l and controls,

through a slow acting relay 23, a relay 21 which applies ringing current vto the input connection of the modulator M1 from the 133 cycle ringing source RS. The relay 24 is also arranged to short .circuit the input winding of the amplifier RA1 toprevent the transmission of 133 cycle ringing current from the detector D1.

In order to provide for relayin rin ing currents incomingl from the main ine L, the circuit 25 leading to the input of the amplifier A1 is associated with the secondary Winding of a transformer 26. The amplifier A1 is arranged to amplify 133 cycle ringing current coming ,from lthe detector D1 and controls, through its output circuit, a relay 27 responsive to 133 cycle ringing current. Relay 27, through a, slow acting relay 28,

vcontrols a relay 29, whereby 16 cycle ringing 23. The 'slow acting relay 23 thereb energizes relay24 which connects 133 cyc e ring-v ing current from a source RS to the input connection of the modulator yM1. Ringing.

current applied to the modulator modulates A the carrier current from the source 12 and TF1 to the common transmitting circuit TL, from which they are impressed upon the line ML through the' transformer 10.

Carrier frequencies modulated by 133 cycle ringing currents at the distant station, after being transmitted over the line. ML, are impressed upon the common receiving circuit RL and passed through the filter RF1 to the input circuit of the demodulator D1. Detected 133 cycle ringing currents now appear inv the output circuit of said demodulator and after being amplified by the amplifier RA1 are impressed through the circuit 25 upon the amplifier A1, which is adjusted to secure proper amplification for 133 cycle currents to operate the relay 27. The operation of relay 27 opens the circuit of `the slow acting relay y28, whiclL in turn closes the circuit of the relay 29. *Relay 29, over its front contacts, applies 16 cycle ringing current to the line L, and simultaneously short circuits the channel TL1 over its up`I front contact closed a short circuit connection across the input of the ampliier BA1. in the receiving channel RLP lThis prevented the possibility of the transmission of 133 cycle current over the channel TL,Y into the common `circuit TL through they transformer l() back into the common receiving circuit RL and through the receiving channel lili, to the relay 27, consequently no false operation ofthis relay can result. 4

By the provision of a supplemental amplilier for the ringing current received over the carrier transmission circuit, the received ringing current ma be amplified to any desired degree suitable for operation of ringing responsive apparatus. rlhe amplier RA, is not satisfactory for 'this purpose, since When this amplifier isadjusted to secure the proper amplification for telephone currents it does not suiciently amplify the received ringing currents. llt Will be obvious that the general principles herein disclosed may be embodied in' many other organizations widely diderent from those illustrated, without departing from the spirit of the invention as defined in the following claims.

What is claimed is:

1. ln a multiplex carrier system, a signaling circuit, av circuit for the transmission of alternately carrier currents, an incomin carrier channel for interconnecting said circuits, said channel including means for translating carrier currents into signaling currents, an ampliier in said channel for amplifying signaling currents, another amplifier associated with said channel for ampliiyin'g ringing 'currents incoming from said carrier transmission circuit, and means responsive-to ringing currents amplified by said second mentioned amplifier for applying ringing currents to said signaling circuit.

2. lln a multiples carrier system, a signaling circuit, a circuit for the transmission of alternating carrier currents, outgoing and incoming carrier channels interconnecting said circuits, saidchannels including means tor translating signaling currents into carrier currents, and vice versa, means responsive to ringing current incoming from said signaling circuit for applying ringing current to said outgoing channel, an am liier in said incoming channel for amplifyingl signal'- current, a second amplilier associated said channel for amplifying ringin currents, andv means responsive to ampli,` ed ringing currents-.incoming from ,said carrier transmission lcircuit tor applysponsive to ringing current incoming from said incoming carrier channel to apply ringing current to said signaling circuit.

4. ln a multiplex carrier system, a signaling circuit, a circuit for the transmission of alternating carrier currents, outgoing and incoming carrier channels interconnecting said circuits, said channels including means for .translating signaling currents into carrier currents, and vice versa, means associated with said signaling circuit and responsive to ringing currents incoming from said circuit to apply ringing currents to said outgoing 'carrier channel, means associated with said signaling circuit tor am liitying ringing currents incoming from sai incoming carrier channel, and means res onsive to such amplified ringing currents or applying ringing current to said signaling circuit.

5. lln a multiplex carrier system, a signaling circuit, a circuit for the transmission ot-alternating carrier currents, outgoing and incoming carrier channels interconnecting said circuits, said channels including means for translating signaling currents into carrier currents, and vice versa, a relay associated with said signaling circuit and responsive to ringing current incoming from said signaling circuit to control the application oiE ringing current to said outgoing carrier channel, means associated with said signaling circuit to amplify ringing current incoming from said incoming carrier channel and a ringing responsive relay associated with said amplifyin means for controlling the application o ringing cunrent to said signaling circuit.

6. lln a multiplex carrier system, a signaling circuit, a circuit for the transmission oit alternating carrier currents, an incoming carrier channel interconnectin said circuits, said channel including means or translatin carrier currents into signaling currents, an

an amplifier associated with said signaling circuit for amplifying ringing currents incoming from said carrier channel.

7. lln a multiplex carrier system, a signaling circuit, a circuit for the transmission of alternating carrier currents, an incoming carrier channel interconnecting said cirt8@ cuits, said channel including means for translating carrier currents into signaling currents, an amplifier for amplifying signaling currents incoming from said carrier e channel and a second amplifier for amplifying ringing currents incoming from said channel.

8. n a multiplex carrier system, a signaling circuit, a circuit for the transmission of alterte Dating carrier currents, an incoming carrier channel interconnecting said circuits, said channel including means for translating carname to this specification this 231' rier currents into signaling currents, an amplifier for amplifying signaling currents incoming from said carrier channel, a second amplifier for amplifying ringing currents incoming from said carrier channel, and means controlled by said second mentioned amplifier for applying ringing currents to said signaling circuit.

In testimony whereof, I have si ed my ay of September 1919.

JHN 'a i SON, JR.

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