US1472849A - Forwarding system foe - Google Patents

Description

Nov; 6,1923; 1,472,849

W. H. MARTEN FORWARDING SYSTEM FOR OCEAN CABLES AND THE LIKE Filed Jun 18, 1918 I k E 1N VEN TOR.

WHMamin B112 S ATTORNEY Patented Nov. 6, 1923.

UNITED STATES PATENT OFFICE.

WILLIAM H. MARTIN, OF NEW YORK,'N. TL, ASSZGNOR TO AMERICAN TELEPHONE AN.

TELEGRAPH GOLMPANY, A CORPORATION 0F NEW YORK.

FORWARDING SYSTEM FOR OCEAN CABLES AND THE LIKE.

Application filed June 18,

To all whom it may concern:

Be it known that 1, WILLIAM H. MARTIN, residing at New York, in the county of New York and State of New York, have invented certain Improvements in Forwarding Systems for Ocean Cables and the like, of which the following is a specification.

This invention relates to transmission systems involving lines of high distortion and attenuation, such as ocean cables, and to the operation of such lines in connection with adjoining land lines. Its object is to improve the operation of signaling over circuits of the character indicated and to provide an arrangement whereby signals over ocean cables may be retransmitted automatically to inland lines.

As is well known, the signal impulses received over such circuits as ocean cables are, because of the characteristics of the line, extremely faint and quite different from the transmitted impulses. They are, generally speaking, too attenuated to affect any but the most delicate recording apparatus and cannot be used in relays for forwarding the signals over other lines. Moreover their wave form is not suited to this purpose.

This invention proposes to combine with ocean cables and like circuits, complete inetallic forwarding circuits designed to transmit faithfully impulses of relatively small amplitude compared with the usual telegraph currents, and to connect the two transmitting circuits by instrumentalities designed to so improve the wave form and increase its amplitude as to make possible the operation of relays for forwarding or recording the messages. Means are also provided for avoiding disturbances of the somewhat delicate system for handling the received impulses, by the more pronounced impulses of outgoing messages in duplex operation.

The invention will be described in coI1- nection with the accompanying drawing in which Figure 1 illustrates diagrammatically one embodiment thereof, and Fig. 2 shows a modification of one detail. The circuit 1 of high distortion and attenuation, here indicated as an ocean cable, is connected through the usual capacity ratio arms 2 and 3 with the artificial line 4 and the incoming signals are taken off at the junction points 5 and 6 of the ratio arms with the main and artificial lines respectively. The conductors 7 1918. Serial No. 240,623.

and 8 for the incoming signals lead to the correcting distortion network 9 which in practice may assume a variety of forms dependingupon the characteristics of the cir-, cuits 3rd apparatus used. It is hereshown as comprising an inductance 10 and resistance 11 connected in series across the circuit, a capacity 12 in series with the circuit which is preferably shunted by an impedance which may comprise inductance 13 and resistance lei and a second shunt across the main circuit comprising inductance 15 and resistance 16, portion of which latter may be shunted by the capacity 17. The effect of this network in general is to produce derivatives of the arrival current which are combined with each other and with the arrival current itself to produce a more efiective form of current wave for recording purposes. The network itself is the invention of another and need not be further described in detail, as it does not per se constitute a part of the present invention.

The effect of the distortion network is to improve the form of the current wave at the expense of current strength, so that the already attenuated signal impulses are further weakened at the output side of this circuit. To correct this condition the current is fed to an amplifier 18 preferably of a thermionic type by which large amplification can be secured without substantial distortion of the current wave. The current is then led to one terminal of the forwarding line 19-20, here indicated as a complete metallic circuit which has the advantage that it is free from the disturbing effect of earth potentials, etc, common in ordinary telegraph circuits and is operable with comparatively weak current impulses. The signal impulses from the amplifier are applied to the center points of impedances 21 and 22, one being located in each side of the metallic circuit. One terminal of each impedance is connected to one side of the metallic circuit and the other two terminals of the impedances are connected to the artificial line N designed to simulate the main line as is customary in repeater circuits and the like where two-way transmission is desired. The impedances 21 and 22 may conveniently constitute the windings of relays for the sending branch of the circuit as indicated in the drawin The recording device 23 at 51c opposite 3 navasse end of the circuit 1920 is provided with duplicate coils, one associated with each side of the line. As here indicated they are connected across the terminals oi impedance elements 241- and 25 which are respectively in series with the opposite sides of the line; and the sending branch 2627 of the duplex set is connected at the center point 0t these impedances. The windings of the recorder 23 may themselves constitute the impedance elements and the sending branch may be connected at their center points if desired as in the case of the impedance elements 21 and 22 which likewise constitute the windings of the forwarding relays. Artificial line N is connected to the opposite ends of impedances 24 and 25 for balancing the circuit 19-20 with respect to the impulses l rom the sending branch 2G27 of the duplex set. The sending device 28 is of the typical -form used in cable transmission having two separate keys or contacts for transmitting, respectively, impulses of opposite sign to the circuit. In series with the sending branch I have provided a device 29 for rounding off the corners of the transmitted impulses at the sending end. The impulses at the sending key are characterized by sudden rises in value and sharp corners at the peak. The sudden changes of current strength indicated by the corners of this curve are entirely lost in transmission over circuits of the kind under consideration, and cannot, therefore, be availed of in the recording instrument. At the same time it is difiicult to prevent these rapid changes from getting into the local receiving circuit which is made sensitive to comparatively weak current impulses, where they have a disturbing effect. The rounding oil device 29 may conveniently consist of an inductance 30 connected in each side of the circuit with a capacity 31 connected in shunt thereto, preferably at substantially the midpoints of the inductance 30. This arrangement of elements will, in accordance with well-known principles, have the effect of rendering less abrupt the sudden changes in current received from the sending device.

As above indicated the impedances 21-22 may conveniently form the windings oi torwarding relays 32 and 33, each Ol' which is a polarized relay having opposite cont acts connected respectively to the positive and negative sides oil the current source 41. The tongues of these relays are connected to the opposite sides 34- and 35 of the transmitting branch of the duplex set for circuit 1, and perform the same function in sending impulses of opposite sign to that line as the keys of the instrument 28 above mentioned. The circuit 3435 is also preferably provided with a device 36 for rounding of the corners of the impulses created by the relays 32 and 33, in the same manner and for the same purpose as the device 29 above described. lnasmuch as the conductor 34: is a ground connection only, it is not necessary to include the inductance elements in that side of the circuit.

The operation of the system will in the main be obvious from the foregoing. Incoming impulses from the line 1 entering the circuit 7-8 will be reformed in contour by network 9 to approximate the wave transmitted, and are amplified in the device 18, whereupon they enter the mid-points of the impedances 21 and 22 where they will divide equally between the main line and the artificial line N ano will consequently not affect the relays 32 and 33. Arriving at the impedances 2i and 25 they will enter the windings or the device 23 and there record the message. Tmpulses transmitted from the sending station 28 will, after being modified by the rounding ofi device 29, enter the center points 01" impedances 2i and 25, there dividing equally between the main line and the artificial line N and accordingly will not affect the receiving instrument 23. The impulses in the conductors l9 and 20 being of opposite sign will oi course oppositely affect the relays 32 and These relays both normally rest upon contacts connected to the same side of the source 34 The impulse in one of the conductors 19--2O will be of a polarity to throw the corresponding relay to the opposite contact and the conductors 3d35 will accordingly be connected to the opposite sides of the source 34, and an impulse oi": corresponding sign will be transmitted to the line 1. This impulse will have its form modified by the device 36 in the same manner as the impulse transmitted from the station 28, and will divide equally between the ratio arms 2 and 3 and the main and artificial lines 1 and 4:, hence not aliecting the receiving branch 7-8 of the duplex set. It is to be noted that the combination oi. the correcting network and the distortionless amplifier especially when used with the closed metallic circuit makes it possible to forward impulses from an ocean cable or like circuit without the interposition of mechanical relays, when desired.

In the modification shown in Fig. 2 the receiving branch of the duplex set associated with circuit 1 is to be understood as similar in all respects to that shown in Fig 1, except that the output circuit of the amplifier 18 is used to operate relays 37 and 38 which send impulses from the source 39 to the forwarding circuit 19-20, instead of transmitting thereto the amplified impulses themselves as in Fig. 1. In this arrangement the windings of the relays 3738 may conveniently be connected in series across the out put circuit of the amplifier thus replacing the primary winding of the transformer shown in that circuit in Fig. 1. The tongues of the relays 37 and 38 are biased by any convenient means such as the springs indicated on the drawing, so that in the absence of current through their windings both would lie against the inner contacts as shown in Fig. 2, but the strength of the springs is so proportioned to the strength of their respective windin s that with a normal current flowing in the output circuit of the amplifier 18 one of the windings overcomes its biasing spring as shown in the relay 38, whereas the other winding is not of suflicient strength to move its contact against the pull. of the spring, as indicated in the relay 37. An increase of current above the normal due to an impulse in one direction in the input circuit of the amplifier will cause the tongue of 87 to move to the opposite contact, thus sending an impulse of one polarity to the line, while a decrease of current below normal so weakens the winding of re lay 38 that its tongue moves under the influence of the spring to the opposite contact, thereby sending an impulse of the op posite sign to the line. In view of the introduction of the new source of current and the relays in this arrangement, it is pret erable to introduce a device 40 between the relays and the circuit 19-2O for rounding oil the corners of the impulses as above described in connection with the devices 29 and 36.

The invention is not to be regarded as limited to the specific arrangement herein illustrated and described, as it will be obvious to those skilled in the art that various changes in the details may be made within the scope oi the invention as here disclosed and claimed.

What is claimed is:

1. In a system for transmitting signals, a transmission line of high distortion and attenuation, a line of comparatively low distortion and attenuation, transmitting mechanism for producing impulses suitable for transmission over said last named circuit, means at the receiving end of said first named circuit for reforming received impulses, as distinguished from regenerating them, so that they have a wave form approximating that at the transmitting end, a distortionless amplifier for increasing the amplitude of the reformed impulses and connecfor applying the amplified impulses i said transmitting mechanism.

2. In a system for transmitting signals, a transmission line of high distortion and attenuation, a receiving circuit connected thereto, a network associated with the receiving circuit for reforming received current impulse to a wave form approximating transmitted impulses as distinguished the impulses, a ;thermionic amplifier having its input circuit connected to the reforming networir and its output circuit connected to a balanced line of low distortion and attenuation.

3. In a system for transmitting signals, the combination with a plurality of transmission lines one of which is characterized by attenuation and distortion, of a connecting circuit comprising means for reforming signaling impulses received over the transmission line characterized by attenuation and distortion and a the anionic vacuum tube for amplifying the reformed impulses and for impressing the said impulses upon another of the said transmission lines.

4;. In a system for transmitting signals, the combination with plurality of transmission lines one of which is characterized by attenuation and distortion, of a connecting circuit comprising means for reforming signaling impulses received over the transmission line characterized by attenuation and distortion, a thermionic vacuum tube for amplifying the reformed impulses and a transmitting mechanism controlled by the said amplified impulses for impressing signaling impulses upon another of the said transmission lines.

5. In a system for transmitting signals, the combination with a line circuit charac terized by attenuation and distortion, of a second line circuit, means to impress signaling impulses on each of said line circuits and a connecting circuit comprising a circuit to reshape the arrival wave of the first line circuit, so that it will be substantially a reproduction of the transmitted wave and a distortionless amplifier to amplify the said reshaped wave and transmitting means controlled by the amplified wave to impress corresponding signals upon the said second line circuit.

6. In a system for transmitting signals, the combination with a line circuit characterized by attenuation and distortion, of a second line circuit, both of said line circuits being adapted for duplex operation, and a connecting circuit adapted to transfer signals from the said first to the said second line circuit comprising a wave reforming circuit and a distortionless amplifier, a second connecting circuit adapted to transfer signals from the said second to the said first line circuit and connecting means adapted to prevent reaction between the said connecting circuits.

In testimony whereof, I have signed my name to this specification this 17th day of June, 1918.

from regenerati WILLIAM H. MARTIN.

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