US874826A - Nullifying disturbances in telegraphic or other signaling circuits. - Google Patents

Description

m- 874,826. PATENTED m0 24, 1907.

E. BLAKENEY &'R. E. OHETW0OD,-JR. NULLIFYING DISTURBANGES IN TELEGRAPHIO OR OTHER SIGNALING CIRCUITS,

APPLICATION-FILED M1229, 190s.

mum-H1 SW i sumes such a' undulatory character that the ceiving elements and thus prevent this dis- T 0 all whom it may concern:

earns Parana: ems-a EDWARD BLAKENEY, OF OSSINING, NEWYORK, AND ROBERT Ev CHETWOOD, JR, OF ELIZABETH, NEW JERSEY, ASSIGNORS TO AMERTUAN TELEPHONE AND TELEGRAPH COMPANY, A CORPORATION OF NEW YORK.

Specification of Letters Patent.

Patented Dec. 24,1907.

Application filed May Z9,1906. Serial No. 319388.

Be it known that we, EDWARD BLAKENEY l and ROBERT E. Cnn'rwoon, Jr., residing at Ossining and Elizabeth, in the counties of Vlestchester and Union and States of New Yuri-a and New Jersey, respectively, have invented certain Improvr-snusnts in Nullifying Disturbances in 'lelegra 'ihic or other Signaling C1 rcuits, of which the following is a speci ficatien.

This invention has reference to the separation oi currents of difierent characters flowing in electrical circuits, and particularly to the nullifying of such disturbancesas may be produced in telegraphic or other signaling circuits by the inductive effect of an adj accnt circuit carrying an alternating current.

Considering a telegraph system in which the relays or other receiving elements are operated by the presence or absence of directv current, it being organized for operation by the normal slowly recurring current impulses of standard Morse signals manually transmitted, if the line has near it a conductor through which passes an alternating current, a similar current will be induced in the telegraph-line which will be superposed upon the operating current. A class of alternating current which is at the present time often encountered is that of single phase and of comparatively low frequency yet high relatively to Morse transmission, say 25 cycles per secend, which is employed for power transmission. The electromotive forces producing such currents are usually extremely high, and, of course, change abruptly from their maximum value to zero, giving powerful inductive effects, yet the frequency is not so great but that the armaturcs of the relays can follow the alternations induced in the line. As a result the operating current assignals are d started and. confused by the vibratlon of the armatures. To exclude the alternating current from the telegraphic returban'c, and to provide a system by which, signals may be eil'ectively tral'ismitted and received without interference or confusion are the principal objects of the invention.

It consists in a means for furnishing separate paths for and confining thereto currents of diverse characteristics, that which. is herein disclosed being in the form of a balance circuit with which the receiving element is associated and which excludes alternating current from said receiving element by virtue oi the establishmentof a condition of equipotential at the extremities of a bridge or cross conductor in which it is placed, while the bridge is thrown out of equilibrium for 0 erating currents and made a portion of tieir exclusive path by the presence of inductive devices in a portion or the branches of the balance circuit to which telegraph currents are relatively impassable.

In order that the invention may be more readily understood, reference is had to the accompanying drawings.

' Figure 1 illustrates diagrammatically a specti'v'ely, to be hereinafter more particularly referred to, and between which extends,

a line conductor L. This conductor is shown 80 as grounded at its, extremities to complete the main circuit, though obviously a complete metallic circuit could be substituted if desired, and ,contains batteries 1) or other suitable-sourees of operating current.

Situated in sucli proximity to the line as to act inductively upon it, is shown a conductor L constituting, for example, a portion of a power-circuit and carrying an alternating current flowing from a generator or other source G, which is of such periodicity that a disturbance will be produced in the telegraph line prejudicial to its operation.

To nullify the effect of parasitic or disturbing currents andprevent the receiving instruments r, whichappear conventionally in the drawings as relays, from being affected thereby, the line L at each station is divided, there being two conductors 10 and 11 connected in parallel to form a section or exten sion of the main circuit they being in series therewith. These parallel branches of the line are s arated into portions 0, d, c and f by a bri ge-conductor 12 connecting the points a: and y in the conductors 10 and 11, respectively, and in the bridge-conductor of each station is connected its relay r. Each of these portions 0, (Z, e, and f when 'eferred telegraph system arranged. in accordance c, d, e,ff the conductors and 1 1 furnishmg the sides, while the conductor 12 rovides the cross wire or bridge. As wel -known, When the fall of potential in, say, the side 0 of-the balance is to that in the side e as the fall in the side (1 is to that inlhe side f, the points a: and y will be of equal potential and no current will flow throu h or rather the most convenient.

electromot'ive torces are balanced in the bridge. Therefore, to nullify the disturbing efiect of the energy existing in the conductor- L while still permitting telegraphic operation, it is onl necessary to secure equality of potential or-alternating currents, while for direct currents the bridge is unbalanced. This result may be attained by so adjusting the impedance of each side that with refers 5: will be satisfied, and by employing in the conductors 10 and 11 at opposite sides of the bridge inductive devices such as condensers which are opaque or impassable to direct currents while transparent or permissive to alternating currents, and including in the companion sides impedance devices allowing currents of both characteristics to pass. In each of the sides 0 and f of the balance-circuit are shown coils I possessing both resistance and inductance, this being referably adjustable, and in series with t 1e coils l in diagonally opposite portions of the parallel branches are condensers C which are shown as being of variable capacity. In each arm d and e is a suit 7 able resistance R, also preferably adjustable, which may or may not be inductive, as is \Vhen the impedance in the various sides is balanced in the manner previously stated, the bridge 12 will be new tral to the induced alternating currents, which will flow through both parallel c0nductors 10 and 11 passing inductively through the condensers, and to ground through the battery, leaving the relaysunaiiected But upon making and breaking the main circuit by means of one of the keys the impulses will pass through the line, and since the condensers are conductively (liscontinuous for, or are impassable to direct ence thereto the equation .slow-changing currei'its, the circuit is unbalanced as far as these are concerned and they flow e-Xcusively through the sides d and e and the bridge-connection those constituting the sole conducting path through the balance the disturbing tion if slight V This may be determined experimentally, or

v be used'in t manner.

In balancing the circuit the frequency of current should be considered,

and, as this is liable to vary, such values of x resistance, inductance -and capacity should be chosen as will not greatly disturb its equachanges in frequency occur.

mathematically by use of t e formula:

by substituting various values of resistance" (r), inductance (l), and capacity (0), until such are found that the impedance will vary but little for the expected fluctuation in the frequency (n). In any event the resistance in the sides (2 ends should be kept as low as possible to avoid cutting down. the operating currents they carry. Also, if practical, that is if such devices for any specific case are not unduly lar e, air-core coils may preferably 1e sides 0 andf, as is illustrated at station A, since their inductance is reasonably constant within a wide range of practical conditions, and with non-inductive resistance in the arms d and e the circuit would remain substantially balanced for any particular frequency, regardless of the magni tude of the induced current. It may be found, however, that to secure the necessary inductance air-core coils are too cumbersome, and in such case those havingiron cores may be employed as is shown at station B. c

There are four po'rtionsof the circuit in which each of the keys is may be placed to effect the transmission of signals-in the bridge 12, Fig. 3, in the line outside the bal ance-circuit, Fig. 2, or in traverse. If located in the first-named position the key is shunted by two circuits of large capacity furnished by the arms 0 d an i e f, respectively, so that although the relay of the sending-operator may respond properly, that of the distant statidn will be sluggish. With the key in the line, ii. the circuit is not properly balanced some of the alternating current may pass through the bridge and the operating current therein becomes more or less undulatory. This being the case the action of the relay is liable to be irregular, as the key may be closed, considering the extremes, at either the period of maximum or minimum current. The most advantageous location for the key is in one of the sides (1 or 0, since when said hey is open the condenser in the other branch conductor is charged by the line batteries and upon closure is discharged, giving a strong current impulse which is suf- 'icient to overcome any lagging tendency of the line current.

llt.

In connection Witheach of iv either ,one of the I sides d or e which the operating currents the keys is shown the usual circuit closer or quency induced currents, comprising two swrtchdc? by wlneh the continuityof the cir- 5 cult may be-preservedwhen ,the operators 2 are not transmitting, The. switch at the station B appears as open; or in the position for'transmission.

Having thus deseribed the invention, we claim:

1. In a telegra hic circuit organized for operation by the. sihwly recurring current impulses of' manually transmitted Morse signals, the combination of a line conductor; branches in parallel with one another forming jointly an extension of said line conductor in series therewith; a bridge conductor uniting said parallel branches; an inductive connection in each parallel branch on different sides of the said bridge, respectively, rendering such portion-of each branch impassable to steady currents and to the said slowly recurring normal current impulses,

' but permitting the passage therethrough of relatively high frequency induced alternatingcurrents; and means for maintaining a potential difference at the extremities of said bridge for the said normal currents, and a condition of equipotential for said induced currents.

v 2. A tele raph system comprising a main circuit, a W eatstone-balance system having its branches connected in the main circuit, a

receiving instrument in the brid e of the balance, and a condenser connecte in a I ortion of each branch at each side of the bri go, and rendering said portions impassable to steady currents.

3. A telegraphic system comprising a main circuit, a W 1eatstone-balance circuithaving its branches connected in the main circuit, a

receiving device inthe bridge of the balance, a condenser connected in a portion of each branch at each side of the bridge, and rendering said portions'impassable to steady currentsand means associated with the branches .for adjusting the balance, substantially as described.

4. The combination in a tele raphic circuit with a line conductor, of parallel conductors forming an extension thereof, a bridge conductor connecting the parallel conductors, a-

receiving elementin the bridge conductor, a condenser in each of the said parallel conductoi s, said condensers being upon opposite sides of the bridge conductor, respectively, and a sending element in one of,the parallel conductors at the opposite s des of the bridge conductor fromthe condenser.v

5. In a system for n'ullifying the disturbing effects in telegraphic circuits organizedfor operation by the normal slowly recurring purrent impulses of standard Morse transmission, of induced alternating currents of'relatively: high frequency, the combination of the telegraph lineconductor; with an inductive c1rcuit station section" for the said higher fresection for the said normal telegraphiccur-c rents constituted of the conductlve portions of said parallel branches, and an interposed 'bridge or cross conductor joinin saidparaili'el branches at points equipotentia with respect to said higher frequency induced currents and between the conductive and inductive portions thereof, said conductively discontinuous inductive portions being on different sides of the bridge in their respective parallel branches; and a'receiving telegraph instrument connected in the said bridge.

6. In a system for nullifying the disturbing effects of induced currents in telegraphic circuits, the combination of the telegraph line with an inductive circuit station section for said induced currents comprising two parallel branches each composed of a conductive and an inductive portion in series, a conductive circuit section for the telegraphic currents composed of the conductive portions of said parallel branches, and an interposed "bridge or cross-conductor joining points of said branches equipotentialwith respect to said induced currents, a receiving telegraphinstruinent connected in the said bridge, and a transmitting instrument in one of the condu'ctive branch portions.

7. In a system for nullifying the disturbing effectsin telegraphic circuits of induced currents of frequency higher than that of the operating telegraphic currents, the combination with the telegraph line,and a station receiving instrument therefor; of a station circuit arrangement organized as a 'Wheatstone-bah ance, with condensers in diagonally opposite portions of the parallel branches of the said balance rendering such ortions conductively discontinuous; the sait receiving instrument being connected in an operative circuit constituting the sole conductive path through the VVheatstone-balance, and composed of the bridge and the other two diagonally 0pposite portions thereof in series, as described herein.

, 8. In a system for nullifying the disturbing effects in telegraphic circuits of induced currents-having a frequency higher than that of the normal operating currents, the combination with the telegraph line, and a station receiving-instrument therefor; of a station circuit arrangement comprising two parallel branches and a bridge conductor joining them and thus organized as a VVheatstone balance; and condensers in die onally opposite portions of the said para lel branches rendering such portions conductively discontinuous, and constituting of the other two diagonally opposite portions of said branches the bridge conductor the sole conducting &i 874,826

path through the said balance; the said re- In testimony whereof, We have signed our 16 ceiving instrument being connected in the names to thisspeci cation in the presence of bridge-conductor between parallel and e uitwo subscribing Wit 'e}sses, this twenty fifth potential points in the paths of said hig er day of May 1906.

5 frequency induced currents, and in series in EDWARD BLAKENEY.

the said sole conducting path of the normal ROBERT E. CHETWOOD JR. elemaphic currents,wherebythe said instru- Witnesses: I

en t is made res onsive to the said normal MILLs E. CASE, currents only, sulistantially as specified. HARRY H. BRIGHAM. I

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