US801936A - Apparatus for the simultaneous transmission of telephonic and telegraphic currents over the same line. - Google Patents

Description

110.801,936. PATENTED OCT. 1'7, 1905. C. TURGHI.

APPARATUS POR THE SIMULTANBOUS TRANSMISSION 0F TBLEPHONIG AND TELBGRAPHIC CURRBNTS OVER THE SAME LINE.

APPLIOATWN FILED JULY 13,1904.

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CARLO TURCHI, OF FERRARA, ITALY.

APPARATUS FOR THE SIMULTANEOUS TRANSMISSION OF TELEPHONIC AND TELEGRAPHIC CURRENTS OVER THE SAME LINE.

Specification of Letters Patent.

Patented Oct. 17, 1905.

Application iiled July 13, 1904. Serial No. 216,374.

Toni/Z whom it may concern:

Be it known that I, CARLO Tnonnengineer, a subject of the King of Italy, anda resident of Ferrara, in the Kingdom of Italy, have invented certain new and useful Improvements in Apparatus for the Simultaneous Transmission ot' Telephonic and Telegraphic Currents Over the Same Line; and I do hereby declare the following to be a `full, clear, and exact description of the invention,such as will enable others skilled in the art'to which it appertains to make and use the same, reference being had to the accompanying drawings, and to letters of reference marked thereon, which form a part of this specification.

My invention relates to enable a double metallic telephone-line e. a telephone-line composed of a wire for the outgoing and a second parallel wire for the return current) to be used eiTectively and advantageously as a conductor for the simultaneous transmission of a telephonic current with another current, hereinafter called the superimposed current,77 without interference between the two currents. The superimposed current may be atelephonic, telegraphic, or high-potential continuous or alternating current. Some solutions of this problem have already been given by Ducousso, Pierard, Caihlo, Swensky, Barret, Jacob, and Gaunt; but my present invention provides a new solution and is able to obviate many important practical diiiiculties presented more or less by the above solutions.

Figure 1 is a diagrammatic view showing the ordinary system for the transmission of simultaneous telephonic and telegraphic messages over the same line. Fig. 2 is a diagrammatic view of a portion ot' my system. Fig. 3 is a longitudinal section through my separator-coil. Fig. I is adiagrammatic view showing a plurality of telephonic systems on a single metallic circuit.

In order to enable this invention to be clearly understood, I shall first proceed to describe its theoretical basis,which is common to the art, with reference to the diagram shown by Fig. l of the accompanying drawings. In this figure, A B and C D are the two linewires of a telephonic line with complete metallic circuit, and T' and T2 are the two telephonic terminals. The points A D at one end of the line are connected to the conductor M H, and the points B and C at the other end I mission of spoken messages.

are connected to the conductor N K. The conductors M H and N K are earthed at their ends H and K. I), situated between H and M, represents a generator of current-tele phonic, telegraphic, or high-potential contineous or alternating current--and Q, situated between K and N represents an apparatus for receiving the current, which will reach the said receiving apparatus through the two wires of the telephonic line in parallel. In general a portion of the superimposed current will pass through the telephones Tl and T2 and produce in them noises having a more or lessunfavorable influence on the etcient trans- In order to obviate such unfavorable inliuence, earlier inventors have proposed to make the resistances of the branches MA M D equal and also to make th resistances of the branches B N and C N equal. By these means the electrical potential is rendered equal at the points A D, and therefore no portion of the current generated at P will flow through the branch A D and through the telephone T. Moreover', if the resistances of the two wiresA B C D are the same no portion of the said current will 'pass through the branch B C and the tele no portion of the telephonic current will pass y through the conductor M IJ to earth, and likewise, for the same reason, no portion of the telephonic current will flow through the conductor N Q to earth.

According to the foregoing general principle a double telephonic or the other line can be employed theoretically as a single conductor for a superimposed current without interference between the two currents; but in practice the arrangement as described with reference to Fig. 1 presents many weak points. First, the two wires of the telephonic line never have exactly the same ohmic resistances, or if their ohmic resistances are exactly the same their respective impedances are not equal; second, the branches A M D and B N C act as short circuits for the telephonic current, and thus considerably diminish the loudness of the transmitted voice.

Earlier inventors proposed various ways of providing the branches A M, M D, B N, C N with resistances in order to reduce so far as IOO possible the amount of the short-circuiting of the telephonic current through the branches A M D and B N C. One inventor proposed an arrangement in which the impedances of the two telephonic lines were made as far as possible equal to each other; but the introduction of resistance in the branches A M, D M, B N, and C N necessarily diminished the strength of the superimposed current. Then some inventors proposed an inductive arrangement by which the resistance of the said branches to the superimposed current was practically unaltered, while the resistance to the short-circuiting of the telephonic current was very much increased.

Having thus explained the theoretical basis (which is common to the art) of this invention, I shall now proceed to set forth the practical disadvantages of the previously-proposed systems.

The first point to be considered when a telephonic line with metallic return is to be employed for a simultaneous superimposed-current service is that there should not be the slightest loss in the telephonic current. Therefore the resistance of the branches A M D B N C should be practically equal to the insulation resistances.

Second. The introduction of such resistances in the branches A M, D M, B N, vC N should not cause the least loss in Athe superimposed current, especially if the latter is a telephonic current. s I

Third. The impedances of the two telephonic lines, as above stated, must be made equal, which they very seldom are in reality. Therefore the system must be provided with means for regulating the said impedances, and in order not to alter the resistance of the wires A B and C D, and thus produce a loss in the telephonic current, such means must be provided in the-branches A M, D M, B N, C N.

Fourth. The electrostatic capacity between the branches A M and M D or B N and C N must be practically m'l, in which respect the earlier systems have been chiefly deficient. Obviously the short-circuiting of the telephonic current may take place not only through vthe ohmic resistances of the branches A M D and B N C, but also through the said electrostatic capacity, which in certain arrangements of the above-described system is very great and is suiicient to cause a .great y loss of telephonic current.

this figure the invention is assumed to be applied to a superimposed telegraph service, but only by way of example. In fact, any other superimposed current may be employed. Referring now to the said iigure, Pis the Morse station, T the receiving-telephone, m the microphone provided with its battery p and its transformer t. The two branches M A and M D are wound on one and the same soft-iron core in the following way to form a separator coil. The two branches are wound together for the greater part of their length, the remainder of the length of each being wound as -a separate coil. Thus M A Y iirst is wound alone -for a length a b on the core S T, and then it is wound as to its remainder c Z on the same core together with the branch M D, as shown more clearly in Fig. 3. Similarly, a portion cf of the branch M D is wound alone, and the remainder g /L is wound together with M A.

So far as possible the coils ab and e f must be equal. The coils c CZ and g /L being wound together are always exactly equal. Furthermore, the two branches M A and M D are wound in opposite directions, so that they have a differential action on the core S T.

The separate or additional coils or windings of the respective branches Aneed not necessarily be made as a whole with the main winding, as described and shown, but they may be separate therefrom.

The ohmic resistances of the branches M A M D are exactly equal, and their inductances are made exactly equal by a very simple arrangement of regulation. The length of the core S T is shown exactly equal to the distance af, so that if, for instance, the inductance of the branch M A should be greater than the inductance of the branch M D the core S T must be shifted by suitable means, such as a screw, to the right. As the inductance of the branch M D does not change while the inductance of the branch M A is lessened, it is obvious that the two inductances can be made exactly equal. shorter than the distance a f-for instance, as indicated by the dotted lines 1/ in Fig. 3-in which case by acting by its movement in oppositew'ay on the two branches the regulation will be rendered more delicate. Thu's by this means of regulation the impedances of the two branches A M D M are rendered exactly equal. 1f now a telegraphic current is generated by the apparatus P,'this current will divide in two parts, each of which will iiow through one of the branches, as indicated bythe black arrows, and as the impedances of the two branches aremade equal and the Abranches are Wound in opposite direction, the self-inductance introduced inthe telegraphic circuit by the above system will be exactly m'l, so that the only alteration in the tele- Cgraphic circuit will consist in the increase of the ohmic resistance, which will be equal to IOO IIO

The core S T might be made IZO ISO

one-half of the ohmic resistance of one of the branches. Thus whatever telegraphic system-simplex or duplex or quadruplexwmay be used its speed will never be reduced.

The result of regulating the branches A M D M, as above described, so as to obtain the same potential at the points A and D is that no portion of the telegraph-current will Aflow through the branch A D and the telephone T will be silent.

The case of a telephonic current flowing through the telephonic circuit will now be considered. Itis assumed that the telephonic current is produced by the microphone m and passes through the transformer tto the branch A D, and thus to the line. A portion of this current will flow through the branch A M D; but as the impedances of the 'branches A M D M are equal no telephonic current will go to earth through M P H. The direction of the current in the derivation A M D, as indicated by the dotted arrows, is such that the inductances of the two branches are added together, and as the mutual inductance between the two branches is practically equal to the self-inductance of one of them, according to the construction of the coil, it can be assumed that the current will flow through a circuit the inductance of which is four times the inductance of one of the branches.

Now since, as above stated, the inductances of the two branches neutralize each other with respect to the superimposed circuit, there will be no difficulty in selecting the self-inductance of each branch in such a way that the four times greater inductance which the current finds in the circuit A M D will act practically as an insulation resistance, so that the loss of the telephonic current through the shunt-circuit is thus rendered practically m'l.

Expressed in figures, the improved apparatus offers to the telephonic current in the circuit A M D an impedance of about three hundred and twenty thousand ohms, while only an additional resistance of eighty ohms is offered to the superimposed telegraphic current.

In order to prevent loss due to the circumstance that the electrostatic capacity between the two branches may be great enough to allow a considerable portion of the current to pass from one branch to the other, the coil is wound as shown 4in Fig. 3. which shows the two additional small coils a e f, used for the regulating device, wound in separate places a b c f and the coils c Z g /t wound together in the central part of the coil /i t.

The wire of the branch A M is representedY by white circles and the wire of the branch D M by hatched circles.

In the ligure the wires of the two branches are shown alternating in each row. Care is also taken that under a convolution of the wire of one branch there is situated a convolution of the wire of the other branch. The electrostatic capacity between the two branches could eXistin two ways: first, by considering each horizontal row as a face of a cylindrical condenser, and, second, by consid- V the two rowsp gu/ q g', each face of such a condenser is neutral, and if also the number of the rows is even the total capacity of the horizontal rows is m'l. Similarly, if two sections, such as man n, n', be considered, the number of the rows being even, then both faces of such acondenser will be neutral, and therefore, the number of the convolutions being even, the total capacity of the sections will be also m'l. Therefore there will be no loss whatever of the telephonic current, while any rapid telegraphic system may be used as the superimposed circuit.

lf, as is usually the case, the-impedances of the two wires of the telephonic line are not equal,they may bemade equal by the regulation of the impedances of the branches M A M D and there will be no loss of telephonic current through M H to earth, because of the high impedance of the derivation A M D, as above set forth.

This invention may be applied to various purposes: first, for superimposed telegraphic, telephonic, orhigh-potential currents; second, for combined telephone-circuits, which problem is too well known to need description;

third, in combination with a system of simul.

taneous telephony and lgelegraphy, the apparatus for which can beincluded in the conductors M H and N K, thus giving three superimposed electrical communications. If the telephone-line in any of such cases is divided in various branches, each of them must be provided at each end with such a separatorcoil in the manner shown in diagram in Fig. 4. In this figure the telephone-line is shown divided. in three sections, at each end of which are placed the separator-coils A Ab AC A1 Ae Af. The telephonic stations are represented by Ta Tl Tc Td Te Tf. vThe current produced by the generator P will first iiow through the telephonic section T Tb, and as the separator-coils must be regulated no disturbances will be produced in the telephones of said section. Then, if the vertex N of the separator of the endB of the first section is connected to the verteX R of the separator ofv the end C of the second section, the superimposed current will iiow through the second telephonic section in a similar manner without disturbing the telephones Te Td, and similarly the third telephonic section will be connected through the conductor S T, thus the superimposed current reaching the receiving apparatus Q without having given any rise to disturbances in the telephones of the three sections, which will remain quite independent one from the other.

IOO

One could easily understand how to proceed if instead of having three telephonic sections their number would have been four, five,

or any number. Y

Having thus described my invention, what I claim as new, and desire to secure by Letters Patent of the United States of America, is-

l. In a superimposed telegraph and telephone system,the combination with a doublemetallic telephone-line and its telephonic apparatus, of a separator coil bridged across the two line-wires, comprising two coils of equal inductance wound together in opposite directions on the same core, and a telegraph branch circuit with telegraphic apparatus leading from a point of the separatorcoil chosen between its two coils, the separator-coil being so constructed as to present no inductive resistance to the telegraph-current and an extremely high impedance to the telephone-current, as hereinbei'ore described.

2. In a superimposed telegraph and telephone system,the combination with a doublemetallic telephone-:line and its telephonic apparatus, of a separator-coil comprising two branches coiled together and separately on the same core, the inductances of the two branches being made equal by means of regulation, and a telegraph branch circuit and its telegraphic apparatus leading to earth from a point of the separator-coil chosen between its two branches, the separator-coil being so constructed as to present no inductive resistance to the telegraphic current and an extremely high impedance to the telephone-current, as hereinbefore described.

3. In a superimposed telegraph and telephone system, the combination with a double-metallic telephone-line and telephone apparatus, of a "separator-coil7 bridged across the two line-wires, comprising two branches wound together in opposite directions on the same core, and two additional coils inserted in each one of the said branches, and a movable core, around which the two branches and the two additional coils are Wound, the inductances of the two branches being made equal by suitably adjusting the movable core, and a branch telegraph-circuit provided with telegraph apparatus, leading to earth from a point of the separator-coil chosen between the two branches, the separator-coil being so constructed as to present no inductive resistance to the telegraphic current and an extremely high impedance to the telephone-current, as hereinbefore described.

4. In a superimposed telegraph and telephone system the combination with a double-metallic telephone-line,and telephone apparatus, of a separator connected across the two line-wires, comprising two branches wound together in opposite directions on the same core, in such a way that the electrostatic capacity between the two branches is m'l, and two additional coils inserted in each one of the branches, and a movable core, the latter and the additional coils forming a means of regulation by which the inductances of the two branches and of the two line-wires are made equal, and a branch telegraph-circuit' with telegraphic apparatus leading to earth from a point of the separator-coil chosen between the two branches, the separator-coil being so constructed and adjusted as to present no inductive resistance to the telegraphic current and an extremely high impedance to the telephone-current as hereinbefore described.

5. In a superimposed telegraph and telephone system, the combination with a double-metallic telephone-line and its telephonic apparatus; of a separator-coil bridged across the two lines and comprising a core, and two branches wound together on the core into a coil with an even number of rows and an even number of sections, the wires of the branches alternating in each row and in each section; and a` telegraph branch circuitfwith a telegraphic apparatus, leading from a point of the separator-coil between its two branches.

6. In a superimposed telegraph and telephone system, the combination with a double-metallic telephone-line and its telephone apparatus; of a separator-coil bridged across the two lines and comprising a movable core, and two branches wound together and separately about the movable core; and a telegraphic branch leading from a point between the two branches.

7 The combination with a plurality of double-metallic telephone main lines and their telephonic apparatuses; of a separator-coil bridged across each main line at both ends thereof and comprising a core, and two branches wound together about the core in opposite directions; and telephone branches leading from a point between each branch of the separator.

The foregoing specication signed at Venice, Italy, this 7th day of June, 1904.

CARLO TURCHI. In presence of- KARL FRANKE, RoBT. W. BLIss, ALPHoNs PRANTOR.

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