In the Matter of Brown's Patent.

"sensitive. When using such self inductive coils it is not necessary to employ "the condensers usually placed in series with the line.

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"My invention also comprises the use of the closed circuit inductive coil or " magnetic shunt, not only for the receiving relay or other receiving instrument "but also for the arms of the 'bridge' used in duplex transmission. For this 5 66 purpose the ingoing current enters the magnetic shunt at its mid-point so that "one half of the said current neutralizes the inductive effect which would be "produced by the other half of said current, and the shunt therefore behaves as a plain resistance. An adjustable contact maker or rheostat may be placed at "the apex' of the bridge for adjusting the 'bridge balance,' whereby the point 10 "at which the current enters the inductive shunt can be suitably altered or "adjusted. Adjustable contacts may also be provided at each end of the "inductive coil so that the number of turns of said coil which constitute the "shunt may be altered as required. Also adjustable external resistances may "be included in the bridge arms for facilitating adjustment and balancing.

"To overcome the difficulties of obtaining and maintaining 'balance' introduced "when working duplex lines with curb transmitters as aforesaid, I may insert "in the 'fork' of the bridge and in series with the receiving instrument a "closed circuit coil possessing suitable self induction and having but moderate "resistance, in order to avoid 'jars' on the receiving instrument.

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"In order that my invention may be clearly understood and readily carried "into effect I will proceed to describe the same more fully with reference to "the accompanying Drawings in which :-Figure 1 is an end elevation. "Figure 2 is a plan and Figure 3 is a side elevation with one pole of the "magnet removed, of relay apparatus constructed according to my invention. 25 "Figure 4 shows a rotary contact surface or drum divided into five sections "insulated from one another. Figure 5 is a side elevation and Figure 6 is a 66 plan of a modification of the apparatus shown in Figures 1, 2 and 3, in "which modification both a fixed tongue and a frictionally controlled tongue "are employed. Figure 7 is a diagrammatic view of a modification of the relay 30 66 apparatus. Figures 8 and 9 are diagrammatic side and plan views respectively, "of another modification of the relay apparatus. Figure 9 is a diagrammatic "plan view of a modification of the arrangement shown in Figures 8 and 9. "Figure 10 is a diagram of a cable circuit in which the receiving instrument "is short circuited by a closed circuit self inductive coil or magnetic shunt. 35 "Figure 11 is a diagram of one end of a duplex cable circuit in which the "receiving instrument is short circuited by a closed circuit self inductive coil or "magnetic shunt. Figure 12 is a diagram of one end of a duplex cable circuit "in which the receiving instrument is short circuited by a closed circuit self "inductive coil or magnetic shunt, and in which a different arrangement of 40 "bridge to that shown in Figure 10, is employed. Figure 13 is a similar diagram to that shown in Figure 10, and shows movable contacts for adjusting "both the bridge balance and the number of turns of the coil constituting the "inductive coil or magnetic shunt. Figure 14 is a diagram of one end of a duplex cable circuit in which curb transmitters are employed and in which 45 "closed circuit inductive coils are placed in the forks of the bridges and "in series with the receiving instruments. Figure 15 shows an inductive coil "having a closed magnetic circuit, suitable for the purpose of my invention. Figure 16 is a cross sectional view of the coil shown in Figure 15. Figure 17 "shows another form of inductive coil having a closed magnetic circuit 50 "and adapted to have its iron core initially excited so as to bring it to a critical state.

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"Referring to Figures 1 to 3,

"A is a light wire coil delicately suspended in the field of a permanent or "electro magnet a. B is a relay tongue fixed to the top of the coil A. C is 55 a rotary disc or drum mounted on a spindle C1 supported from the frame of "the instrument by suitable bearings. This drum C is made in sections

In the Matter of Brown's Patent.

"separated by insulating material c which may be a metal ring of suitable width "having its sides covered with insulating material, or may consist of thin mica "insulation. The free end of the tongue B bears lightly upon the rotary drum "C and should be of a width not exceeding the width of the insulating strip c. 5 "The main line conductors E, E are connected to the coil A by very fine wire "coils. One end of the relay circuit F is connected to the sections of the drum "C by a divided battery and suitable brushes, ff, and the other end of the said relay circuit is connected to the tongue B. G is a recording instrument in the "relay circuit. c is a pulley which is mounted on the drum spindle C1 and 10" which is connected to any suitable source of power for rotating the drum C. "bb are adjustable screw-stops carried by the frame of the instrument, for "limiting the lateral movements of the tongue B. al is a lug projecting from "the bottom of the coil and a2 a' are springs having their ends respectively attached to the lug a1 and to the frame of the apparatus.

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"The coil A is normally suspended so that its plane is parallel to the north "and south line of the magnet a, in which position the tongue B is in contact "with the insulating strip c, that is to say, the tongue is in its zero position. "The arrival signalling current from the main line circulating in the coil A, 66 turns this coil out of the north and south line of the magnet a (to a extent 20" which depends upon the strength of the said current) and moves the tongue B laterally into contact with one of the sections of the rotary drum C, thus "making contact and enabling a current to pass through the relay circuit.

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"The object of rotating the drum C is to reduce the friction between it and "the end of the tongue B to a minimum, so that very minute forces may be 25" enabled to move the said tongue as above described.

"The rotary drum C may consist of any suitable number of insulated sections, "such number of sections depending upon the required properties of the relay. "For instance, (as shown in Figure 4) when it is required to adapt the instru"ment for receiving signals over lines where the signals are likely to possess 20 "what is known as 'a varying zero,' such as would be caused by the charging up "action of a receiving condenser, the drum C may be divided into five sections, c, c2, c3, c, c3, insulated from one another by suitable material. c is the central "insulation ring or piece forming the mechanical zero of the instrument as "previously described. When the tongue B moves into contact with either of

In the Matter of Brown's Patent.

"the divisions or sections c2 or c1, a signal is indicated as previously described. "If the tongue B is caused by the arrival current to move too much to one or "other side owing to the said varying zero, the said tongue makes contact with "one or other of the sections c3 or c (which may be termed correcting sections). "These sections c3 and c are so arranged that when they are thus in contact 5 "with the said tongue, not only does the signal continue to be indicated in the same manner as if the tongue were resting on section c2 or c1, but an auxiliary "relay is also worked; this auxiliary relay works in conjunction with the main relay and causes a correcting current to be sent through a few auxiliary turns "of wire wound on the coil A, in such a direction as to cause the tongue B to 1066 move back towards the insulating strip or piece c to such an extent as to make. "the electrical zero as far as possible coincide with the mechanical zero of the "instrument.

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"If the relay circuit is constructed for receiving cable signals, it may in order "to facilitate the reading of the signals (especially with hand sending) be most 15 "conveniently fitted with two contact-making tongues, one fixed to and the "other frictionally controlled by the suspended coil, the motion of the fixed "tongue either to right or left changing over the connections for the frictionally "controlled tongue.

"Such an arrangement is shown in Figures 5 and 6, in which A is the 20 "suspended coil, B is a tongue rigidly fixed to the said coil and B' is a tongue "having a hole in it through which passes a rod a3 fixed to the coil A. The "rod a3 is screw threaded and carries a screw nut a1 at its upper end. The tongue B' rests upon a boss of insulating material a and is there retained "by the spring a, one end of which bears on the under side of the nut a'. The 25 tongue B' is thus frictionally attached to the coil A.

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"The tongues B and B1 at one extremity bear upon the rotary drum C and at "the opposite extremity are connected to one end of the relay circuit F.

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G, Gare the recording instruments. bb are stops for limiting the lateral movements of the tongue B and are stops for limiting the lateral 30 "movements of the tongue B'. The magnet a and remaining parts of the "apparatus are omitted from these figures but are arranged as in Figures 1, "2 and 3.

"The recording instruments are so arranged that in order to produce a signal "the tongue B, B1 must both be on the same section of the drum C at the same. 35

5

In the Matter of Brown's Patent.

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time, the current passing in a similar manner along both. "is shown in Figure 6.

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Such position

"When the arrival current causes the coil A to turn as previously described, "both the tongues B and B1 are caused to slide into contact with one section of "the drum C and give a signal in the relay circuit; after a very slight movement however the tongue B' is arrested by the stop b', the tongue B "being permitted to continue its movement under the influence of the coil A, "owing to the fact that the tongue B' is only frictionally attached to the said "coil. Upon the coil A returning to its normal position the tongue B1 will 10 immediately be carried to or across the insulated strip c thus breaking contact "and registering the signal. If the next signal is of the same sign, the tongue "B1 will be again carried over to the same section of the drum, even though the amplitude of oscillation of the coil A may not have been sufficient to cause "the fixed tougue B to return to zero between the signals. For an opposite 15 signal these tongues operate in a similar manner, the tongue B being moved "to the opposite side or section of the drum and the connections thus reversed. "In this manner the connections for the frictionally controlled tongue B1 are "changed and a very clear definition of the signals may be obtained.

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"These two tongues may be arranged on two separate instruments, the fixed tongue on one, and the frictionally constrained tongue on another. Or the "tongues, operated by a single coil, may make contact with two separate rotary "drums.

"Referring to Figure 7. A is the coil suspended in a plane parallel to the "north and south line of the magnet and adapted to receive the arrival currents 25" from the main line E. C is the rotary drum the sections of which are divided "by insulating material c and connected to one end of the relay circuit F, and

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In the Matter of Brown's Patent.

"G is a recording instrument all as previously described. H is a suspended rod provided with a cross piece h. hh are silk cords or their equivalent "connecting the ends of the cross piece h with the top of the coil A. B is the tongue which is fixed or frictionally attached to the suspended rod H, and has one of its ends connected to one end of the relay circuit and its other end 5 bearing on the rotary drum C. When no arrival signalling current is received "the tongue B rests upon the insulating strip c, and when the coil A is turned "by the arrival signalling current from the main line, as previously described, "such_movement is communicated through the cords h1 h', cross piece h, and "rod H to the tongue B, which latter is caused to slide into contact with one or 10 "other of the drum sections and cause a current to pass through the relay "circuit. By placing the ends of the cords h1 h1, which are attached to the "coil A, as far apart as possible, and their opposite ends, which are attached to "the cross piece h, closer together, the end of the tongue B may be caused to move through a greater angle than the coil A, and its movement thus 15 "exaggerated.

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"These cords do not however form part of my invention.

"Referring to Figures 8 and 9, the suspended coil A connected to the main "line E, the magnet a, the tongue B connected to one end of the relay circuit, "and recording instrument G, are arranged as in Figure 1. The rotary drum C 20 "is made in a single piece, revolves in a horizontal plane, and has the other end "of the relay circuit connected to it by a suitable brush f. When no arrival "current is being received from the main line, the tongue B remains out of "contact with the rotary drum as shown clearly in Figure 9. When the arrival "current from the main line passes through the coil A and causes it to turn as 25 "previously described, the tongue B is moved into contact with the drum C "and thus causes a current to pass through the relay circuit.

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"It is obvious that instead of employing only one drum C as shown in Figures 8 and 9, two such drums may be employed. Such an arrangement is "shown in Figure 9a in which two drums CC connected to one end of the 30 relay circuit by a divided battery, are arranged in a position parallel to one "another and having a space between them. In this space the end of the "tongue B is normally situated and is adapted to be moved by the arrival sig66 nalling currents so as to make circuit with one or other of said drums. "Referring to all the foregoing Figures, it has been found that the contact 35 "between the end of the relay tongue or tongues and the rotary drum is not "quite constant in amount, especially when the point of the tongue bears lightly on the said drum. Any variation in the strength of the current "passing, due to this cause, may be greatly reduced by short circuiting the "sliding contact between the tongue and the drum by a condenser K of suitable 40 66 capacity.

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"If the zero of the signals received from the main line is found not to be "constant in position, owing for example to the charging up action of a receiving "condenser, the relay can be fitted with auxiliary coils arranged in parallel "with the working coil A and receiving current from a secondary circuit; this 45 "latter current is before passing to the auxiliary coil previously sent through "suitable contacts (either moving or fixed) and a circuit having resistance, "induction, or capacity, or any combination of these to reproduce the same "variable effects in on the zero, but in the opposite direction, and thereby "eliminate this disturbing factor or variation in of the zero, from the working 50 of the relay.

"The rotary drum may be caused to spin by any convenient means, for "example I may fix the armature of a small electro-magnet directly on the "drum shaft. Any means, (other than the coil described), which are at present "known to the art may be used to impart the necessary motion to the tongue of 55 "the relay for the purpose of indicating received signals.