US1762754A

US1762754A - Phantom carrier circuit

Info

Publication number: US1762754A
Application number: US276895A
Authority: US
Inventors: Harold S Black
Original assignee: Western Electric Co Inc
Current assignee: AT&T Corp
Priority date: 1928-05-11
Filing date: 1928-05-11
Publication date: 1930-06-10
Anticipated expiration: 1947-06-10

Description

June l0, 1930. H, s. BLACK 1,762,754

PHANTOM CARRIER CIRCUIT Filed May l1, 1928 Arron/ver Patented June 10, 1930 UNITED STATES PATENT OFFICE HAROLD S. BLACK, OF EAST ORANGE, NEV JERSEY, ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK PHANTOM CARRIER CIRCUIT Application filed. May 11,

This invention relates to Wave transmis sion, and especially to phantoming multiplex systems, as for example carrier Wave signaling systems.

Considering, for example, terminal apparatus for a pair of two-conductor lines each transmitting voice frequency Waves and carrier Waves, when it is desired to phantom the lines for either voice or carrier Waves, or both, for instance in the general manner disclosed in the patents to Affel 1,582,112 and 1,582,113 and OLeary 1,582,073, all issued April 27, 1926, it is desirable to avoid deleterious effectsin the phantom circuit or circuits due to inclusion therein of side circuit filters used for frequency separation of the voice frequency waves and carrier frequency Waves.

It is an object of the invention to avoid such deleterious effects While economizing apparatus for effecting frequency separation of the different messages intended for the different signaling channels, respectively.

It is also an object to, at the same time, economize With respect to the number of phantom coils required.

In one specific aspect the invention is a multiplex Wave transmission system having side circuits with side circuit low frequency grouping filters and side circuit high frequency grouping ilters in the side circuits. and'having a phantom circuit for lov.T frequency Waves, and/or a phantom circuit for high frequency Waves derived from the side circuits at such points thereof that Waves pass through the low frequency phantom circuit Without passing through the side circuit loW frequency grouping filters and/or Waves pass through the high frequency phantom circuit Without passing through the side circuit high frequency grouping filters. All of the filters mentioned may be of the usual construction, as may also any filters used in the phantom circuits to effect frequency selection or separation of low frcquency and/or high frequency Waves intended for the 10W frequency and/or high frequency phantom circuits respectively. The use of side circuit filters and phantom circuit filters of usual construction tends 'to- 1928. Serial No. 276,895.

Ward economy of filter apparatus, by facilitating an economical design of the individual filters.

The points in the side circuits at which the phantom circuits are derived may be at the junction of the transmission lines with the side circuit grouping filters. Thus, a given set of phantom coils may be employed for both phantom circuits, since the, Wares intended for the phantom circuits are derived from the side circuits before frequency separation of the low frequency Waves and the high frequency waves intended for the phantom circuits.

Other objects and aspects of the invention Will be apparent from the following description and claims.

Fig. 1 is a diagram of a system embodying one form of the invention; and

Fig. 2 is a diagram of a system embodying another form of the invention.

Referring to Fig. 1, HFL and HFL represent tyvo telephone lines, each comprising a pair of conductors Which may be phantomed in a 'Well known manner so that each pair of conductors acting in parallel operates one side of a phantom circuit. The phantom connections are established by means of

transformers

10 and 10, from the middle points of whose windings taps ll and 11 are led to form the phantom terminals of the system.

In order that the line HFL may be employed for carrier transmission, a branch CL, is provided which leads to carrier equipment of any type well known in the art, and in this branch a high pass filter 12 is iucluded. This high pass filter is of the broad band type which freely transmits a band of frequencies Within certain limits, While sharply attenuating and suppressing the frequencies lying Without the limits of the band. The filter' is so designed as to pass the various carrier frequencies employed in the system together with their associated side bands, but it will not permit ordinary voice currents transmitted over the line EFL to pass into the circuit CL3. The ordinary voice currents transmitted over the conductor HFL must be separated from the Cil vcarrier frequencies and transmitted through cies are thereby prevented from entering the voice side circuit VLB.

In a similar manner, the line HFL is provided with two branches, one leading through the high pass filterV 14 to the side carrier circuit GL and the other leading through the low pass filter 15 to the voice side circuit VL.

The arrangement so far described is that ordinarily employed for -superposing a vplurality of carrier channels on an ordinary voice channel. It is possible toY phantom a pair of circuits of this type for ordinary voice transmission by meansof the

phantom coils

10 and 10 with their phantom conductors 11 and 11. The voice currents transmitted over the phantom, in so far as any unbalance occurs between the two conductors ofthe side circuit, are prevented from entering the carrier circuit, such as the circuit CLS, by the high `pass filter. The effect upon the phantom of the filter LFS in the two conductors of the side circuit in introducing impedance due to the series coils y connection by introducing` phantom coils,

such as 20 and 20" between the lines HFL and HFL and the high pass filters 12 and 14. Conductors 211 and 21 are led from the midpointsof `the phantom coils, as indicated, to form the phantoincarrier terminal CLI, which leads to suitable carrier equipment. With this arrangement, the Aphantom carrier currents need not be transmitted through the impedance of any of the side circuit filters.

In order to provide 'the necessary frequency separation between the voice currents transmitted over the phantom and the carrier currents transmitted over the phantom, a low pass filter 16 is. included in the voice phantom terminals VLP and a high class filter f1-7 vis included in the carrier phantom terminal CLD. These lters, are similar to noisy or unbalanced line, and therefore serve to reduce .noise caused, for example, by induction from power lines Vvinto lines HFL and HFL or by static7 picked up in thoser lines.

Condensers 23 connected between the halves of the line windings of

transformers

20, 20Y and 22, facili-tate transmission of ringing currents of, for example, 2Ol cycles or 133 cycles, from or to the lines HFL and HFL. c

Fig. 2 shows another form of the invention. Parts having the same reference characters in the two figures are identically alike in structure and function. The filters 12 to 15 of Fig. 2 are similar in structure and function to the filters .12 to, 15 respectively, of Fig. 1, but may be of cheaper design, for reasons indicated hereinafter. n

Thus, the system of Fig. 2 comprises the lines HF L and HFL each transmitting voice and carrier frequencies, the side circuit low frequency grouping` filters 13 and 15, the side circuit high frequency grouping filters .12 and 14', a phantom circuit VLp for low frequency waves and a phantom circ uitCLp for carrier or high frequency waves. These phantom circuits are derivedV from the side circuits .at the junctions of the transmission lines HFL and HFL with the side circuit grouping filters, by employing phan,

tom coils

30 and 30 for both phantom circuits. The low frequency Waves and the carrier waves intended to be transmitted from the transmission lines HFL and HFL to the phantom circuits VLp and CLI, are derived from the transmission lines before frequency separation ofY the low frequency waves and the carrier frequency waves; and Y these derived low frequencyV waves and carrier waves are separa-ted by the filters 16 and 17. Y

Thus, the phantom circuits VLp and CLp are derived from the side circuits at the line sideof the side circuit grouping filters 12', 13', 14 and 15, so that the phantom circuits do not include side circuit grouping filters. Therefore, the deleterious effects which would result from inclusion of such filters are avoided. Y c

The

transformers

30 and 30, and transformer 33, reduce deleterious noise effects,

as noted of

transformers

20, 20 and 23 in Fig. l.

ln Fig. 2, since the low frequency phantom path does not include the low pass filters of the side circuits, any dissymmetry in those fnterscannot introduce impedance in the low frequency phantom circuit. Therefore, the filters 13 and l5 can be of cheaper design than the filters 13 and l5. Further, under conditions usual in practice, inclusion of low pass filters of side circuits in low frequency phantom paths introduces suiiicient impedance to cause objectionable distortion or degradation of signal quality, and moreover, upset the impedance balance between the voice phantom circuit VLl, and its balancing network at the voice phantom circuit repeater hybrid coil or bridge transformer. (T he repeater with the hybrid coil and the balancing network are not shown in the drawing, as it will be understood that it can be connected to the voice phantom circuit in the usual way).

In both figures of the drawing, all of the filters can be of the usual construction.

TWhat is claimed is:

l. A multiplex wave transmission system comprising side circuits, side circuit low frequency grouping filters and side circuit high frequency grouping filters in the side circuits, and a phantom circuit derived from the side circuits at such points thereof with relation to said side circuit filters that Waves transmitted over said side circuits pass through the phantom circuit without passing through either side circuit filter.

2. A multiplex wave transmission system comprising side circuits, side circuit low frequency grouping filters and side circuit high frequency grouping filters in said side circuits, a phantom circuit for low frequency waves, and a phantom circuit for high frequency waves, both derived from said side circuits at such points thereof with relation to said side circuit filters that waves intended for said phantom circuits leave the side circuits before Afrecpuency separation of the low frequency waves and the high frequency waves intended for the phantom circuits.

3. A multiplex wave 'transmission system comprising side circuits, side circuit low frequency grouping filters and side circuit high freiluency grouping filters in the side circuits, and a phantom circuit derived from the side circuits at such points thereof with relation to said filters that the impedance of neither filter 'is included in the phantom circuit, each of said filters comprising` series and shunt paths, and certain of said shunt paths consisting of ay single reactance element.

4. A system comprising two side circuits and a phantom circuit derived therefrom, said side circuits including` transmission lines and physical paths selective of waves of a given frequency range, one of said paths having one end connected to one of said lines, and the other of said paths having one end connected to the other of said lines, said system also comprising, in addition to said side circuits and a voice wave phanton'i circuit derived therefrom, said side circuits including voice wave transmission lines and voice wave physical paths selective of waves of given characteristics, one of said paths having one end connected to one of said lines, and the other of said paths having one end connected to the other of said lines, said system also comprising, in addition to said side circuit selective paths, a physical path for voice waves, included in said phantom circuit and selective of waves of given characteristics and connected to said ends of said side circuit selective paths, so that the latter paths are not included in said phantom circuit.

6. A system comprising two carrier wave side circuits and a carrier wave phantom circuit derived therefrom, said side circuits including carrier wave transmission lines and carrier wave physical paths selective of waves of Given characteristics, one of said paths having one end connected to one of said lines, and the other of said paths having one end connected to the other of said lines, said system also comprising, in addition to said side circuit selective paths, a physical path for carrier waves, included in said phantom circuit and selective of waves of given characteristics and connected to said ends of said side circuit selective paths, so that the latter paths are not included in said phantom circuit.

i. A system comprising two signal transmission lines each adapted to transmit voice waves and carrier waves, a voice wave sine circuit including one of said lines, a voice wave side circuit including the other of said lines, a voice wave phantom circuit derived from said lines, and a carrier wave phantom circuit derived from said lines, said voice wave side circuits including voice wave physical paths selective of waves of given characteristics, one of said voice wave paths having one end connected to one of said lines, and the other of said voice wave paths having one end connected to the other of said lines, said system also comprising, in addition to said side circuit voice wave selective paths, a physical path for voice waves, included in said voice wave phantom Uli ite

vso

circuit and selective of waves of given characteristics and connected to said ends of said side .circuit voice wave fselective paths so that the latter paths are not included in said voice wave phantom circuit, said carrier wave side circuits including carrier wave physical paths selective of waves of given characteristics, one of said carrier wave paths having one end connected to vone of said lines, and the other of said carrier wave paths having one end connected to the other of said lines, said system also comprising, in addition to said side circuit carrier wave selective paths, a physical path for carrier waves, included in said carrier wave phantom circuit and selective of waves of given characteristics and connected to'said ends of saidV side circuit' carrier wave selective paths, so that the latter paths are not included in said carrier wave phantom circuit.

8. The method which comprises transmitting different messages of different frequency ranges respectively over one path, transmitting different messages of different frequency ranges respectively over a second path, transmitting messages over said two paths in parallel, deriving from the two paths said messages transmitted over the two paths in parallel, to the exclusion of said other messages, and thereafter effecting frequency separation of said messages of different frequency ranges transmitted over the one path'and frequency separation ofjsaid messages of different frequency ranges transmitted over the second path.

9. The method which comprises transmitting different messages of different frequency ranges respectively over one path, transmitting dierent messages of different frequency ranges respectively over a second path, transmitting different messages of different frequency ranges, respectively, over the two paths in parallel, deriving from the two paths said messages transmitted over the two paths in parallel, to the exclusion of said other messages, and thereafter effecting frequency separation of said niessages of different frequency ranges transmitted over the two paths in parallel, frequency separation of said messages of different frequency ranges transmitted over the one path, and frequency separation of said messages of different frequency ranges transmitted over the second path.

In witness whereof, I hereunto subscribe my name this 10th day ofMay, 1928.

HAROLD S. BLACK.