US243288A - Duplex telegraph - Google Patents

Description

(No Model.)

G S MOTT 'Duplex Telegraph.

180.243.288.v Patented Junel 21, 1881.

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UNITED STATES PATENT OFFICE.

GARRET S. MOTT, OF PHILADELPHIA, PENNSYLVANIA.

DUPLEX TELEGRAPH.

SPEC?IZEICA'LION forming part of Letters Patent No. 243,288, dated June 21, 1881. Application led September 30, 1880. (No model.)

tery from affecting the home rela-y on the open ing or closing of the transmitter; and the objects of my invention are to simplify and improve the operation and construction of the system, and to insure the presentation to the incoming current at each station of the same amount ot' resistance under all circumstances, irrespective of the changes of circuit. These l objects I attain in the manner Iwill proceed to describe, reference being had to the accompanying drawings, in which- Figure 1 is av diagram illustrating my improved system of duplex telegraphy, and Fig. 2 a diagram of a modified arrangement. Each of these diagrams illustrates the arrangementY of transmitter, batteries, resistance-coils, and

circuits at only one station, but as the same arrangement exists at the other station it has not been deemed necessary to illustrate it.

Referring to Fig. 1, T is the transmitter; B, an ordinary relay; M B, the main battery; E B, the equalizing-battery'; R h, an adjustable rheostat or resistance coil or box, and G the ground or earth connection.

The armature of the transmitter T consists of a lever, A, pivoted at p, and having its opposite ends insulated from each other, and to each is secured a flat spring, s, (s,) on an insulated support, the free end of the spring, when in its normal position, (as indicated on the diagra1n,) bearing against the inner face of the hook-shaped end a (a) of the lever, while an adjacent stop, m, (m,) is adapted to bear on the spring and break its contact with the end a (a) ofthe lever-armature when the latter is attracted by the electromagnets of the transmitter. The line-wire is connected with the stop m through the wire b and the main battery, and with the end a' of the armature-lever through the wire b, while the spring s is connected, through the wires d d, with the relay B, which is grounded through the wire el. The equalizing-battery E B is vconnected with the stop m through the wire e, and the spring s is connected, through the wire f, rheosta-t R lt, and wire d', with the relay, while the end a of the armature-lever is connected with the ground through the wires e and f', a ground-comme tion for the battery E B being made through the wires e2 andf. When -the transmitter T is open-that is, when its armature is not attracted to the electro-magnets-the incoming current from the line goes to the relay through the wire b', end a' ofthe armature-lever, spring s', and wires d d', and thence to the ground, 'while the main battery M B, having no connection through the stop fm', is thrown out of circuit. At the same time the equalizingbattery E B, having no connection through the stop m, is also out of circuit. On the other hand, when the transmitter is closed the incoming current goes to the relay R through the battery M B, wire b, stop m', spring s', and wires d d', and thence to earth.

In order to neutralize the effect on the relay ofthe current from the main battery M B at the home station, as it ows through the relayto earth on the closing ofthe home transmitter, the action of the equalizing-battery is brought into play. At the saine moment that the attraction of the armature A to the magnets of the transmitter brings the stop m' into contact with the spring s and breaks the Contact between the arm a' and spring s the spring s at the opposite end of the armature-lever is brought into 'contact with the stop m, and the connection between the spring s and arm a is broken, so that a current from the battery E B flows through the wire e, stop m, spring s, wire j', rheostat R h, and wire d', and through the relay R to the ground, the circuit being completed by the current which flows through the wires e2 and f from the battery to the ground. The current which enters the coils of the relay from the equalizing-battery E B is of opposite polarity from that which flows in the same direction from the main battery M B at the home station, andthe resistanceR his so proportioned as to make both currents of equal strength, Vso that the effect of one current on the relay ICO is neutralized by that of the other. Hence, owing to the fact that these two equal but opposing currents are caused to simultaneously enter the coils of the home relay in the same direction, and to be drawn off simultaneously, the relay is not affected in any way by the action ofthe holnetransmittcr, but responds only to currents sent over the line from the battery' at the distant station, and so records signals only from the transmitter at that station, the main batteries at the two stations, ot' course, having their opposite poles to the line. Hence the incoming current from the main battery at the distant station passes to the ground through the home relay in the same direction and with the same polarity as the currentfrom the home relay.

I prefer to put on the wire b a small resistance-box, i, presenting to the incoming current a resistance equal to that which it has to overcome in passing through the main battery M B when it ows over the wire b. A similar resistance, r', may also be put on the wire e', for use in connection with the battery E B.

In the i'noditication, Fig. 2, the principle of the invention and the method of operation are the same. as described above; but the construction ot' the transmitter is somewhat changed, two electromagnets, or two sets of electromagnets,being combined with two independent armatures, a a', so as to cause the short-circuiting of the two batteries M B and E B, instead of throwing them out of circuit when the transmitter is opened, as in the arrangement described above. The pivoting-point ot' the armature a is connected through the wire b with the main battery M B, and through the wires d d with the relay, while the line-wire, also leading to said battery, is connected through the wire b with a stop, against which the armature a bears when the transmitter is open. The equaliZing-batteryE B is grounded through the wire f', and connected, through the'wire f, rheostat B h, and wire d', with the relay, as bet'ore, and is also connected through one' wire, e, with the pivoting-point of the armature a, and through another Wire, e', with a stop, against which the said armature bears when the transmitter is open. When the transmitter T is open, therefore, the main battery' M B is short-circuited through the wire b', armature a', and wire I), while the battery E B is short-circuted through the wire c, armature a, and wire e. When the transmitter T is closed, however, and the short circuits opened, a current from the battery M B flows to earth through the coils of the relay, while a current of equal strength, but ot1 opposite polarity, from the battery E B simultaneously enters NVitnesses the coils of the relay in the same direction, and so neutralizes the effect ot' the current from the main battery.

It will be observed that in both modifications the adjustable rheostat or resistance-box R h is never thrown out of circuit, and no matter whether the transmitter throws the equating-battery in or out of that circuit, the continuity ot' such circuit, so far as the rheostat B h is concerned, is never interrupted, and an equal resistance is presented to the incoming current under all circumstances. In the arrangement shown in the diagram Fig. l,t'or instance,the rheostat B h has always a groundconnection through the wiresfandf, whether the armature-lever of the transmitter be in the position shown, or be closed to throw the battery E B in circuit. VHence that portion of the incoming current which passes from the wire d to the wire j'always meets the same amount ot' resistance under all circumstances.

I claim as my invention- 1. A sta-tion for a duplex-telegraph system' in which line-wire, transmitter, main battery, and ordinary relay between said battery and the ground are combined with an equalizingbattery of opposite polarity and a resistance and circuits, substantially as described, whereby the opening of the home transmitter throws the main battery oft' the line, while the closing ot' the said transmitter throws the said battery on the line and grounds it through the home relay and simultaneously throws a cnrrent from the equalZing-battery through the same coils ot' the relay in the same direction.

2. A duplex-telegraph system in which the relay is between the main battery and the ground at each station, and the main batteries at the two stations have opposite poles to the line, whereby the main battery at one station passes to the ground through the home relay in the same direction and with the same polarity as the incoming battery from the distant station.

3.',In a duplex-telegraph system, the combination of line-wire, transmitter, main and equalizing batteries, relay, rheostats i' and 1", and circuits, substantially as described, to present to the current from the distant station resistances equal to the internal resistance of f said batteries.

In' testimony whereot'I have signed my name to this specification in the presence of two sub- `scribin g witnesses.

GARBET S. MOTT.

JAMES F. To'BIN, HARRY SMITH.

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