US1606131A - Carrier-wave signaling system - Google Patents

Description

Nov. 9 1926.

H. M. PRUDEN CARRIER WAVE SIGNALING SYSTEM Filed Oct. '7 1925 RBF lnven/or: H o/d/ lP/z/de/v by .A/fy

Patented Nov. v9, 1926.

UNITED STA HAROLD M. PBUDEN, OE WYOMING, NEW JERSEY, ASSIGNOR TO WESTERN ELECTRIC COMPANY,'INCOBIPOBATED, OF NEW YORK, N. Y., A. CORPORATION OF NEW YORK.

CABRIEILWAVE SIGNALING SYSTEM.

Application med October 1, 1925. Serial No. 60,864.

. This invention relates to carrier wave signaling systems and particularly to ringing circuits therefor.

An object of the invention is to simplify the transmission of ringing signals in carrier telephone systems.

The invention is particularly, but not ex,-

1 with a ringing current, provided, of course, the side band produced by such modulation ,lies'within the transmission range of, the

terminal band filter.

This method of transmitting. ringing signals is facilitated in the present invention by the provision of a novel circuit for connecting a voice frequency composite ringer to the terminal of a carrier telephone channel without unbalancing the associated .hy-

. brid circuit. The invention 'efiects a mate: rial saving' in apparatus, and possesses the further advantage that it may be rea applied to existing carrier systems without otherwise changing the system.

The accompanying drawing is a diagrammatic illustration of one terminal of a multiplexv carrier wave telephone system embodying the invention.

The drawing'shows the necessary circuits which would enable one to conduct a complete two-way conversation from low fre-' quency line L over to a distant station, and to transmit and receive ringing signals over the multiplex line.

The low frequenc line L may be an ordinary subscribers te ephone circuit. A radiating conductormay, of course, be employed in place of the line ML when it is desired to apply the invention to radio systems.

The low frequency line L is associated with the transmitting channel TC and the receiving channel RC of the carrier system through the usual hybrid coil H and associated balancing network N. Additional transmitting and receiving channels may also be provided, as indicated. The transmitting channel TC includes the modulator M, oscillator TO and band filter TBF. Receiving channel RC includes dethe multiplex line M1 bell,

modulator and amplifier DA, oscillator R0 and band filter RBF.

The modulators associated with the various' transmitting channels throughout the sistem are of the balanced typedisclosed in t e U. S.,patent to Carson, No. 1,343,306,

issued June 15, 1920, designed to suppressthe unmodulated carrier from transmission. The various demodulators and amplifiers "may be of the well known vacuum tube detector type shown in Fig. 49 ofan article .entitled Carrier current telephony and telegraphy by Messrs. Colpitts and Blackwell, ublished in the Transactions of the American Institute of Electrical Engineers, V01. 40, 1921.

The carrier system outlined above is, as

stated, of the type in which the carrier wave of each channel is su pressed from transmission when nosigna are being sent, and whensignals are being transmitted modulation components of the modulated wave are sent .over the line, but no unmodulated components of the carrier wave are transmitted.

In order to reproduce the signals from.

modulated waves of this character, it is necessary that the carrier wave supplied to the' demodulator at the receiver be of substantially the same frequency as the carrier wave which was suppressed at the transmitter. A system of this general character is described in connection with Fig. 49 of the Colplitts and Blackwell article, supra".

T e various band filters associated with the terminal' transmitting and receivin' channels are so designed that the wil transmit one of theside bands, either t e upper or lower as desired, produced by modulation,in the respective channels, and will suppress from transmission frequencies lying outside of such band. These filters may be designed in accordance with the principles setforth in the U. S. patent to. Camp- No. 1,227,113, issued May 22, 1917.

The hybrid coil H is of the well known balanced type including three windings,'inductively related to each other. One wind-, ing may be called a series winding andthe/ other two, line windings. Tappedofi from an intermediate point of each line. winding 1 is a bridge circuit, which in the present case that, when the proper values of impedance are connected across the several terminals, energy impressed upon the series Winding will not affect the bridge circuit and vice versa. For a further description of hybrid coils reference may be had to an article by Messrs. Gherardi and Jewett entitled Telephone repeaters published in the Transactions of the American Institute of.

Electrical Engineers, Vol 38, N o. 11, October 1919 From the above, it will be seen that voice currents originating in the low frequency line L will pass through the line windin s of the hybrid coil H into the modulator M 1n the transmitting channel TC. There is likewise fed into the modulator the carrier current from the oscillator TO. Of the components of modulation appearing in the output circuit of the modulator M, the band filter TBF suppresses all except one side' band, for example, the upper side band, which it transmits to the multiplex line ML. The waves so transmitted over the line ML are picked up by one'of the receiving band filters at the distant terminal and transmitted to the appropriate receiving channel.

The waves incomin over the line LIL of the frequency assigne to channel RC pass through band filter RBF and are combined in the demodulator and amplifier DA with carrier waves from the source R0. The voice frequency components of demodulation appearing in the output of receiving channel RC are inductively im ressed upon the line windings of the hybri coil H and divide substantially equally between the low freqlpency line L and the balancing networ N.

The hybrid coil H has four pairs of terminals, terminals 1 being associated with the series winding, terminals2 and 3 being associated with the line windings, and terminals comprising thebridge circuit terminals. The generator G provides a source of IOOO-cycle ringing current periodically interrupted at the rate of 20 cycles per second for the purpose of transmitting ringing signals as modulations of the carrier frequency allotted to any channel of the multiplex system. This might be accomplished by connecting the generator G across the bridge circuit terminals 4. but this procedure would materially increase the cost of the system and unnecessarily complicate the circuit for reasons hereinafter more fully 'described. If, on the other hand, the generator G were connected directly to the line terminals 2, the resistance of the generator would unbalance the hybrid circuit during the ringing operation and it would accordingly be necessary to substitute a network simulating the impedance of the generator G for the line balancing network N, which would also increase the cost of the system.

, The present invention provides a novel and inexpensive switchingarrangement for transmittin the ringing current from the generator diagonally through the hybrid coil H to the modulator M, over substantially the same conduetorsas are utilized in receiving ringing signals, and at the same time opening both the line and network sides of the hybrid coil during the ringing period in such a way that the resistance of the generator does not unbalance the hybrid circuit.

When it is desired to transmit ringing signals to the distant station, the local operator or subscriber impresses a 20 cycle ringing current upon the low frequency line L, this current be ng impressed over the back contacts of relay 5 upon the alternating current relay 6.

The operation of relay 6 establishes an energizing circuit for relays 7 and 8, which may be traced from round, through battery' 9, windings of re ays 7 and 8 in series, left contact and armature of relay 6 to ground. An energizing circuit is likewise established for relay 10, extending from ground, through battery 11, windings of relays 10 and 8 in series, left contact and armature of relay 6 to ground. Relay 12 .is also operated over a circuit extending from ground through battery 13, winding of relay 12, right contact and armature of relay 6 to ground.

The operation of relay 7 disconnects the low frequency line L from the terminals 2 of the hybrid coil H. The operation of relay 10 disconnects theline balancing network N from the terminals 3 of the hybrid coil. In actual practice, the functions of relays 7 and 10 have been performed vby a single relay, and it will be understood that separate relays are shown in the drawing merely for the sake of simplifying the showmg.

Relay 12, in operating, opens its right back contacts, thus disconnecting the receiving ringing apparatus from conductors 14 through which such apparatus is normally connected to terminals 2 of the hybrid coil H in readiness to receive incoming ringing signals. At its. right front contacts relay 12 connects the generator G to the conduc tors 14. Relay 12 in opening its left back contact, also opens the circuit of ringing re sponse relay 15 in order to prevent the operation of relay 5 during the transmission of ringing signals. This latter precaution is taken to prevent transient capacity effects from actuating the receiving ringing circuit when the ,input leads are open during the energization of relay 12.

Relay 8, when energized over the circuit traced above, disconnects the right conductor 14 from the lower line terminal 2 of hybrid coil H, and connects this conductor to the lower line terminal 3. Under these conditions, the 1000-cycle ringing current periodically interrupted at 20 cycles is supplied from generator G to the modulator Mover a circuit extending from one pole of generator G through one right front contact and armature of relay 12, conductor 14, upper terminal 2 and line winding of hybrid coil H, left bridge terminal 4, modulator M, right bridge terminal 4, line winding and lower terminal 3 of hybrid coil H, front contact and armature of relay 8, conductor 14, right armature and front contact of relay 12 to the opposite pole of generator G.

The ringing current thus supplied to the modulator M modulates the carrier current supplied to the modulator from the oscillator TO, and one of the products of modulation, for example, the upper side band, is transmitted by the band filter TBF to the multiplex line ML. The manner in which the ringing signal is received at the distant terminal will be described in connection with the local terminal circuits shown ,on the drawing, since the circuits at the local and distant terminals are identical.

In receivin ringing signals allotted to the channel It the side band incoming over the line ML will lie within the transmission range of band filter RBF. The wave so transmitted by the filter RBF is combined in the demodulator and amplifier DA with carrier waves from the source R0 to produce the original ringing frequency of 1000 cycles interrupted at 20 cycles. The ringing current in the output circuit of the demodulator and amplifier DA is transmitted through .hybrid coil H and is selectively transmitted by tuned circuit 17 to the input circuit of detector 18. The 20 cycle com: ponent appearing in the output circuit of detector 18 is impressed upon polarized relay 19 which is actuated alternately by the positive and negative impulses.

Upon the operation of relay 19 in the above manner, alternating current relay 20 is energized in the manner described in Murphy Patent No. 1,537,653, issued May 12, 1925, remaining energized as long as relay 19 is operated in response to the incoming signals. Relay 20, in operating, short circuits relay '21 which is normally energized over an obvious circuit. Relay 21 is of the slow releasing type and is adapted to close its associated contact only when relay 20 remains energized for a predetermined period, and hence relay 21 will not be deener-' gized if relay 20 is momentarily operated in response to voice currents or other irregular impulses incoming over the line.

Relay 21, inv deenergizing, establishes an operating circuit for relay 15 which extendsv through the left armature and contact of relay 12. Hence, if the left contact-of relay 12 is open, as it is during the transmission of rin ing signalsto the distant terminal as descri ed above, relay 15 can not be enerquency line L and the balancing network N from the hybrid coil H to prevent singing in the carrier circuits. The operation of relay 5 also disconnects the low frequency line L from the alternating-current relay 6 to prevent the actuation of this relay during the reception of signals.

From the above description, it will be seen that by transmitting the ringing current diagonally through the hybrid coil, it is unnecessary to substitute a net work which simulates the impedance of the 1000 cycle generator for the line balancing network during, the signal transmitting operation.

Since substantially the same conductors 14 are utilized in the transmission and reception of ringing signals, itwill be .seen that this system involves fewer connections between the carrier system and the ringing circuits than if the ringing enerator were connected directly to the bri ge circuit terminals of the hybrid coil.

While only one embodiment of the invention has been shown and described, it will be understood that all embodiments, as defined by the appended claims, come within the scope of the invention.

What is claimed is: 1

1. A signaling system comprising a transmission line, outgoing and incoming branch circuits, a plurality of impedance elements connecting said line and said branch circuits in conjugate relation, means for disconnecting said line from said branch circuits, and means controlled by said first mentioned means for transmitting a signal over a path including inseries the outgoing branch circuit and certain of said impedance elements.

2. A signaling system comprising a transmission hne, an outgoing branch and an incoming branch, a plurality of impedance elements connecting one of the branches in bridge of the line and theother branch in series with' the line, means for balancing said line to permit independent communication between the line and said branches, means for disconnecting the line from said branches and for simultaneously impressing a signal on said outgoing branch, and means controlled by said last mentionedmeans to establish a' path for the outgoin signal inproduce a neutral effect with respect to said incoming branch.

3. A carrier wave signaling system compllSlllg a transmission line, an outgoing channel and an incoming channel, ahybrid' -coil connecting said outgoing channel in bridge of the line and said incoming channel in series with the line, a line balancing network connected to said hybrid coil, and means for disconnecting said line and balancing network from said hybrid coil and for transmitting a signal over a path including in series said outgoing channel and a portion of the windings of said hybrid coil 4. A carrier wave signaling system com prising a low frequency line, an outgoing channel andan incoming channel, a hybrid coil connecting said outgoing channel 7 inbridge of the line and said incoming channel in series with the line, a line balancing network connected to said hybrid coil, a

ringing circuit including a pair of conductors normally bridged across the drop side of said chybrid coil to receive incoming ringing signals, switching means for disconnecting said low frequency line and balancing network from said hybrid coil, means controlled by said switching means for disconnecting one of the conductors of said ringing circuit from the drop side of the hybrid coil and connecting it to the network side of the hybrid coil, and means for impressing a ringing signal upon said ringing circuit for transmission over a path including in series said outgoing channel and a portion of the windings of said hybrid coil.

In witness whereof, I hereunto subscribe my name this 6th day of October A. D.,

' HAROLD M. PRUDEN.

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