US1361486A - Composite signaling system - Google Patents

Description

H. S. OSBORNE AND R. D. PARKER.

COMPOSITE SIGNALING SYSTEM.

APPLICATION FILED DEC. 11, I9I8.

1,361,486, Patented Dec. 7, 1920.

Inventors Jttorney UNITED STATES PATENT OFFICE.

HAROLD s. osEoENE, OF NEW YORK, A D EALzEMoNn n. PARKER, or BROOKLYN,

NEW YonK, ASSIGNORS 'ro AMERICAN TELEPHONE AND TELEGRAPH GOM- PANY, A CORPORATION or NEW YORK.

coiviPosrrE SIGNALING SYSTEM.

Application filed December 11, 1918.

1 '0 all whom it may concern:

Be it known that we; HAROLD S. OSBORNE and RALZEMOND D. PARKER, residing at New York and Brooklyn, respectively, in the counties of New York and Kings respectively, and State of New York, have invented certain Improvements in Composite Signaling Systems, of which the following isa specification.

This invention relates to composite signal transmitting systems such, for instance, as are used for simultaneously sending telephone and telegraph messages over the same wires. Its object is to improve the efficiency of such systems and to render such service available over circuits of certain characters where it has heretofore beenimpossible.

It has long been common practice to simultaneously transmit telephone and telegraph messages over the same wires. In the past, however, the telephone circuits so used have in general had a rclatively small number of loading coils. The actual use of such compositesystems has furthermore been limited to cases in which the telegraph was used with a ground return; 7

Telephone currents are of the order of one inilli-ampere while telegraph currents 'areordinarily of the order of eighty milli-amperes. It has been found that when telegraph currents of this magnitude are superimposed on high eiliciency telephone lines embodying many loading coils and the amplifiers now inuse,"tl1at the telephone current is interfered with to such an extent as to render it unlit for commercial purposes in some cases wholly unintelligible. This is particularly true of very long cable circuits in which the total number of loading coils is large and the amplifiers are operated with very large amplifications.

The undesirable effect upon the telephone current is due primarily to the effect of the relatively large telegraph currents on. the permeability of the iron cores of the loading coils resulting in a very great change in their apparent resistance to the telephone currents. Also the higher harmonics of the telegraph impulses when magnified by the high power amplifiers now in use affect the telephone circuit if these harmonics are not kept very small in magnitude. In accordance with this invention, it is proposed to overcome these diliiculties by first reducing the Specification of Letters Patent.

Patented Dec. 7, 1920;

Serial No. 266,326.

magnitude of the telegraph currents to the order of the telephone currents or even less .and then by employing a complete metallic the high frequency components of the telegraph iinpulsesin order to avoid interference with telephone communication. This means that the telegraph current will come to its operating value at a comparatively slow rate and the speed of signaling is necessarily limited. By using a metallic circuit for the combined telephone and telegraph circuit and reducing the value of the telegraph current as above indicated, the danger of interference with the telephone circuit by the high frequency components of the telegraph impulses is so diminished that it is possible to use a composite set designed to pass a telegraph current wave reaching its operating value sooner than under the old system, and therefore giving increased speeds of operation without interference with the telephone conversa lion. An advantage also arises from the fact that the telegraph currents of a single telegraph circuit pass through both windings of the loading coils 'of the telephone lines instead of through one winding only as in the grounded circuit, since at the higher speeds of signaling the loading coils will then be an advantage as in telephone communication, instead of detriment.

The invention will be more fully understood by reference to the accompanying drawings in which Figure 1 is a reproduction from. an oscillograph record showing the interference of telegraph impulses with telephone currents and Fig. 2 shows diagramm'atically a circuit such as may be used in employing the present invention.

In Fig. 1, A represents a telegraph current and B the telephone current as it is affected graph lines the telephone line is provided by the loading coils in the circuit, when a telegraph current A of the magnitude heretofore used is superposed on the circuit. For the purpose of illustration the telephone current is here represented as of a constant frequency of 800 cycles. It will be noted that there is a diminution of telephone current each time there is a rapid change in the value of the telegraph current as at the points 00, each of these producing its well identified effect in B at points y. The results evidenced at y lag slightly behind the points of rapid change in the telegraph current as will be seen from the drawing. This diminution is known as the flutter effect on the telephone circuit and is caused by the action of the telegraph currents upon the loading coils. This effect may be so great in some cases as to practically suppress the telephone current.

Referring to',Fig. 2, 1 represents a typical telephone circuit embodying loading coils 2 and repeaters 3. At each end of the circuit is represented a telephone set 44, for sending and receiving telephone messages and a telegraph apparatus, 55, for sending and receiving telegraphic signals. The telephone apparatus illustrated is of a well known type and needs no detailed description. In the telegraph sets 6 represents the receiving relay and 7 in sending key. Each of these is in practice associated in a well known manner with the usual relays, (not shown).

At the juncture of the telephone and telewith series capacities 8 and shunt induc tance 9 and the telegraph line with series inductanees l0 and shunt capacity 11, which serve to prevent the telephone impulses from entering the branch leading to the telegraph instruments and the telegraph cur rents from entering the branch leading to the telephone instruments.

The elements of this composite set 'located in the telegraph branch will, in accordance with this invention, be designed to permit the passage of frequencies corresponding to the increased rate of telegraph signaling which as above noted is possible with the arrangement herein described without interference with the telephone communication. The windings of relay 6 are divided between the opposite sides of the circuit and are connected between the line 1 and the artificial line N. The sending apparatus 7 is connected to the opposite sides of the line at the midpoints of the relay winding 6 so that impulses emanating therefrom will have no eilect upon the -re ceiving relay since they divide equally and traverse in opposite directions the two halves of the winding. The groupof series inductances and shunt capacities indicated at 12 serve to partially suppress the high freitsra'pidly varying components without interfe'rence with the telephone circuit.

It will be apparent then that the invention herein'described beneficially affects both the telephone and the telegraph transmission in a composite system, in that it removes defects which. the telegraph current introduces in the telephone transmission under present practice and at the same time increases the speed and reliability of the telegraph transmission.

' The nature of the invention and the manner of operation will be clear .trom the foregoing without further description. It will be understood that the circuit here shown is illustrative only, as the invention may be employed with a wide variety of circuit arrangements within thespirit of the invention and the scope of the appended claims.

What is claimed is:

. 1. The improvement in the art of composite telephony and telegraphy which consists in producing telephone signaling currents of the usual character, producing telegraph signaling currents so proportioned as to be of the same order of magnitude as the telephone currents, orsmaller, and concurrently transmitting said telephone and telegraph currents over the same pair of conductors.

2. The improvement in the art of com posite telephony and telegraphy which consists in proportioning the constants of a pair of conductors to eflic'iently promote the propagation of telephone currents producing telephone signaling currents, and imposing them upon said conductors, and producing telegraph currents so proportioned to said telephone currents as to be or, the

currents over the same pair of conductors,

and amplifying said telegraph currents at one or more points on the line.

4. The improvement in the art of composite signaling which consists in producing telephone and telegraph signaling currents so proportioned asto be of the same order of magnitude, and concurrently transmit-' ting said signaling currents over the same pair of conductors, and separating the telephone and telegraph currents into separate channels at the receiving stations.

5. The improvement inthe art of composite signaling Which consists inproducing telephone currents of the order of five milliamperes, producing telegraph currents of the same order of magnitude, or smaller, and concurrently transmitting said telephone and telegraph currents over the same complete metallic circuit.

6. The improvement in the art of composite signaling Which consists in producing telephone signaling currents of the usual order of magnitude, producing telegraph currents of the same order of magnitude, or smaller, imposing said telephone and telegraph currents upon the same pair of conductors, and increasing the sending rate of the telegraph signals to a point above that possible With usual telegraph currents of the order of 80 milliamperes, and to a degree sufficient to profit by the characteristics of the conductors designed to efiiciently propagate the telephone currents.

In testimony whereof We have signed our names to this specification this ninth day of December, 1918.

HAROLD S. OSBORNE. RALZEMOND D. PARKER.

Images