US2055638A

US2055638A - Communication system

Info

Publication number: US2055638A
Application number: US734180A
Authority: US
Inventors: Elliot M Staples
Original assignee: Bell Telephone Laboratories Inc
Current assignee: AT&T Corp
Priority date: 1934-07-07
Filing date: 1934-07-07
Publication date: 1936-09-29
Anticipated expiration: 1953-09-29

Description

' Sept. 29, 1936. E. M. STAPLES COMMUNICATION SYSTEM Filed July 7, 1954 4 SheetsSheet 1 M m T W5 M E A T ORNE) sfipi. 29, 1936. M, STAPLES 2,055,638

COMMUNICATION SYSTEM Filed July '7, 1934 4 Shets-Sheet 2 wvbvrola EM. STAPLES Sept. 29, 1936. 'E. M. STAPLES COMMUNICATION SYSTEM Filed July 7, 1934 4 Sheets-Sheet 5 Sept. 29, 1936. E. M. STAPLES 2,055,638

COMMUNICATION SYSTEM Filed July 7, 1934 4 Sheets-Sheet 4 lNl ENTOR EM. .5 TAPL 5 Patented Sept. 29, 1936 UNETED STATE-S PATENT OFFICE COMMUNICATION SYSTEM Application July 7, 1934, Serial No. 734,180

22 Claims. (Cl. 179-43) ihis invention relates to communication systems and more particularly to a line network over which different types of signals may be transmitted.

5. The invention has special reference to leased lines, that is, to the case where a network is provided and then turned over to a customer to be operated and controlled by him.

An object of the invention is to provide a. net-- 10 work which includes means for interconnecting a series of lines at a number of points in such manner that various types of signals as well as control currents may be transmitted from any one of the lines to any number or all of the other lines, with means for splitting it at selected points to thereby divide the network into a plurality of sections each of which may be operated independently of the others.

As an example of a practical embodiment, the

invention will be described as applied to a network for use in a telephotograph or picture transmission system and to a station at which. six lines are interconnected. Control currents may be. transmitted to condition the network for broad- 25 casting picture or speech currents,v or the net'- work may be used for two-way telephone conversations from a station associated with any one of the lines to stations associated therewith and. with the other lines; the interconnecting station being n provided with a splitting arrangement, whereby the network may be divided into: two sections.

having three lines associated with each section.

It is to be understood that any number of linesmay be interconnected at a splitting station, that 35, splitting may be so effected that difierent numbers of lines may be associated with the respective portions of the sections local to the splitting station, and that the splitting arrangement. may be used with a network including either four-wire or two-wire lines.

According to the embodiment to be-described' in detail, a central ofiice of the company supplying. the service, which includes an arrangement for interconnecting six lines of a. network, also includes apparatus for splitting the network. This oifice is connected to a customers local station by means of two pairs of terminal loops over which telephotographic and broadcast speech currents, as well as network conditioning; control currents, may be transmitted and received, and two-way telephone currents may be transmitted, to or from. all lines when the network is not split and to or from each section independently when the net work is split, and a loop circuit including means 5;, for controlling the splitting apparatus.

A detail description of the invention follows and is illustrated in the attached drawings in which:

Fig. 1 is a schematic showing a central ofiice at an interconnecting point;

Fig. 2 is a schematic illustrating a customer's station local to the central office;

Fig. 3 shows a two-wire line connection to the splitting station which may be substituted for that tothe right or left of section line XX of Fig. 1; and

Fig. 4 illustrates a different arrangement for use at a central ofllce.

By placing Fig. 1 above Fig. 2 there is provided a diagram of a complete station at an interconnecting point which embodies the invention.

The following description is based on the assumption that the telephotographic sending apparatus at the respective stations of the system operates to produce and supply to the line the lower side-band of a picture modulated carrier current, which may extend over a frequency range from. about 1000 cycles to 2600 cycles, and that direct current control currents may be transmitted from any station of the system, including that local to the splitting ofilce, by simplex or composite connections over the circuits respectively employed for similarly directed picture modulated or speech currents.

Referring to Fig. l, W is a west line, E is an east line, N1 is a first north line, N2 is a second north line, L1 is a first pair of terminal loops connecting the central ofiice to the customers station, L2 is a. second pair of terminal loops connecting the central ofiice to the customers station and L is a loop over which the splitting relay is controlled.

At the central office, the west and east lines are connected through a composite set and repeating coil I, the upper path of the two-way repeater 3, a bridge circuit arrangement 4, the upper path of a two-way repeater 5, a bridge circuit arrangement- 6, the upper path of a two-way repeater I, a repeating coil and composite set 8, for one-way transmission through the central ofi'ice, and, for the oppositely directed transmission, by a composite set and repeating coil 9, the lower path of the two-way repeater 7, bridge circuit arrangement 6, the lower path of the two-way repeater 5, bridge circuit arrangement 4, the lower path of the two-way repeater 3, and the repeating coil and composite set H. The respective transmission paths described above are connected to the north line N1 and N2 and the local station terminal loops L1 and L2 through the

bridge circuit arrangements

4 and 6. The composite set I, and other similar sets, comprise the usual choke coils and condensers associated with the line as shown. These sets terminate in conductive paths over which direct current signals may be transmitted.

Bridge circuits 3 and 5 are of the type disclosed in U. S. Patent 2,019,603 of C. W. Green issued November 5, 1935. Briefly, these bridges are designed to provideconductive paths for interconnecting several four-wire or two-wire lines, with the two-wire lines all connected to the bridge on a four-wire basis, so that each transmitting line may transmit into all the other receiving lines except its own receiving line and, as tothat, it is substantially conjugate. For a complete disclosure of the design and operation of these bridges, reference may be made to the above menpicture receiving machine R.

Signals may be transmitted from the sending machine S, with key H3 in normal position as shown, via conductors 23, the two adjacent left hand levers and normal contacts of key 24, conductors 25, the two right hand lower normal and lever contacts of key is, conductors 26, the two lower left hand normal and lever contacts of key 58, lower repeating coil 16, conductors 2? of the loop circuit L1, the upper repeating coil is, the upper transmitting path of repeater l3 and conductors 23 to the bridge arrangement t.

For two-way telephone conversations, the key i8 is thrown to the right and thereby moves its left hand lever contacts out of engagement with the normal contacts associated with the respective levers and into engagement with the alternate contacts respectively associated with them. Conductors 28 and i9 are thereby open-circuited and hence the picture receiving and transmitting machines are disconnected from the respective circuits of the terminal loo'ps L1, and the receiver and transmitter of the telephone set 22 are connected to these loop circuits, respectively. The telephone. receiver is connected via conductors 2 i, the two upper left hand alternate and lever contacts of key it and conductors ill to the upper repeating coil it and the telephone transmitter is connected via the conductors 29 and the two lower left hand alternate and lever contacts of key 58 to the lower repeating coil E5.

The sending and receiving machines S and R, respectively, or the transmitter and receiver of a second telephone set 22A may be connected through the terminal loops L2 to the bridge arrangement 6 over circuits similar to those described above for loops L1.

For picture reception at the local station over loop L2, key 26 is actuated to disconnect the receiving machine from conductors l9 and to connect it to conductors 35. Incoming picture currents are transmitted from the cable bridge 6 via conductors 36, lower path of repeater 3i, lower repeating coil 32, conductors $38, upper repeating coil 33, the two upper right hand lever and normal contacts of key 36, conductors 35 and the alternate and lever contacts of key 20 to the receiving machine.

For picture transmission from the local station over loops L2, key 24 is actuated to disconnect the sending machine S from conductors 25 and to connect it via conductors 23, the two left hand lever and alternate contacts of key 2 3, conductors 35, the two lower left hand normal and lever contacts of key 3 3, conductors 26a, the two lower right hand normal and lever contacts of key 34,

thelower repeating coil 33, conductors 92, upper repeat-ing coil 32, upper transmitting path of repeater 3i and conductors 3'! to the bridge arrangement 6.

For'two-way telephone conversations, the key 3 1 is thrown to the left and thereby disengages its right hand lever contacts from the associated normal contacts and engages these lever contacts with the alternate contacts respectively associated with them. Conductors 26a and 35 are thereby open-circuited, the picture sending and re ceiving machines are disconnected from the sending and receiving loop circuits L2, and the telephone transmittcr and receiver of set 22A are respectively connected to these loop circuits. The telephone transmitter is connected via conductors 29A, the two lower right hand alternate and lever contacts of key 34, lower repeating coil 33, conductors 92, the upper repeating coil 32, upper transmission path of repeater 3i and conductors 31 to the bridge arrangement 6. The telephone receiver is connected via conductors 2 5A, the up per right hand alternate and lever contacts of key 3 3, upper repeating coil 33, conductors 96, lower repeating coil 32, lower transmission path of repeater 3i and conductors 38 to the bridge 6. Obviously incoming telephone currents are transmitted from the bridge 5 via conductors 35!, etc., as traced in the preceding sentence, to the receiver of the telephone set Keys I8, 34 and 2d are provided with additional contacts which control the supply of current impulses to a circuit including means actuated by these impulses to condition apparatus units associated with the difierent lines, as will be hereinafter set forth, and also to control the supply of current to local circuits which include means for indicating traffic conditions in the network at all times during the operation of the system.

If the attendant at the customers station desires to talk one way to all stations connected to the network, he first throws key 48 to the left to break the connection through the right hand normal and lever contacts and complete circuits through the associated alternate contacts. This serves to cause the right hand lever contacts of keyl8 to disengage their normal contacts to thereby open the circuit through conductors 25 and hence disconnect the sending machine S from the outgoing loop L1, and to force these lever contacts into engagement with their alternate contacts, whereby the transmitter of the telephone set 22 is connected via conductors 29 and I26, the two lower right hand alternate and lever contacts of key l8, conductors 26, the two lower left-hand normal and lever contacts of key H), the lower repeating coil l6, and through the outgoing circuit of loop L1, as traced above for the sending machine S, to the bridge arrangement 4. At the same time the upper right hand key lever is separated from its normal contact and engages its-alternate contact to apply ground to conductor 37, which connects through the secondary winding of the lower repeating coil 95, loop conductors 27, the lefthand winding of upper repeating coil l4, conductor 38 and the lefthand winding of relay 39, to one terminal of battery 49, the other terminal being grounded. Current flow from battery 40 over the above described simplex circuit operates the relay 39, the armature 4! of which is pulled up to apply ground to the conductor 42. This conductor is connected via conductor 43 to a direct current repeater 44 associated with the west line at the central office, and over the armature t5 and conductor 46 to a direct current repeater ll associated with the east line at the central office and also to similar direct current repeaters (not shown) associated with the north lines N1 and N2 via conductors 43 and 43. Since these direct current repeaters are all of the same design and operate in the same manner, the following description of that shown at 44 will apply to the others.

Current flows from the battery 53 of repeater 44 through the windings of relays 5i and 32 connected in series, conductors t3 and 42, armature 4! to ground at the direct current repeater associated with loops L1 and thence to the other terminal of battery 5E8. Relay El operates to short circuit the upper output circuit of alternating current repeater 3, while relay 52 operates to reverse the connection of battery 53a and thereby reverse the direct current supplied through conductors 53 and composite set of equipment ll, included in the lower pair of line wires of the west line and thence over these conductors to polarized relays, associated with alternating current repeaters included in the section of the line connecting this station repeater to the next station repeater to effect certain control functions at the line repeaters, and through polarized relay 56 of the direct current repeater associated with the next western station. Since the line repeaters and their mode of operation are not a feature of this invention, they are not further described. Relay 53 is operated to apply ground to a conductor, similar to conductor 43, whereby its relay 5! is operated to short circuit the upper output leads of the alternating current repeater at this station, and its relay 52 is operated to apply control current of desired sign to the lower conductors of the next section of the west line, whereby the alternating current line repeaters and the next western station repeater are controlled as described above. This cycle of operation will be repeated at each of the succeeding alternating current line and station repeating points of the west line.

In a similar manner, direct current repeater ll will operate to short-circuit the lower, or input, path of line repeater l and to reverse the current supplied over the upper pair of wires of the adjacent section of the east line to control the line repeaters and the direct current repeater at the next eastern station, in the manner described above for the west line, and so on for the line and direct current repeaters at the successive alternating current station repeating points in the east line. The line and direct current repeaters associated with other lines radiating from the splitting station, for example, lines N1 and N2 will be controlled in an identical manner, as will be the line and direct current repeaters associated with all lines included in the network.

Instead of using key iii, the attendant could have used key S t, in which case the microphone of telephone set 22-A would have been connected through the outgoing repeating coil windings of 33 and 32 and associated path of alternating current repeater 3! to the bridge arrangement 6,

and ground would be applied to conductor 51 to control the operation of the direct current repeater 58, identical with the direct current repeater associated with terminal loop L1, which in turn operates through the direct current repeaters 4i and Hand like repeaters associated with the north lines N1 and N2 to control all of the direct current repeaters associated with all lines included in the network and, by virtue of the operation of these repeaters, to control the alternating current repeaters associated with all lines, in the manner described above for the west line.

All stations are connected to the network either directly, or through bridges, by means of connections similar to loops L1 or L2. As a result of the operation of the direct current repeater preceding each of these stations, the conductor corresponding to 4342, will be grounded and relays 59 and 63 of the terminal loop repeater will be operated. Relay 59 will short circuit the output circuit of the alternating current repeater l3, and relay 89 will apply ground to the circuit including conductor 38, upper winding of repeating coil M,.conductors 21, secondary winding of the lower repeating coil [8, conductor 31, upper right hand lever of key I8, which will be in normal or non-operated position at each of the terminal stations, and hence this lever will engage its upper normal contact to complete a circuit through conductor E2, armature 63, conductor 65, relay 66, conductor 61, left-hand winding of upper repeating coil !8, conductors l5, left-hand winding of lower repeating coil M, conductor 68 to battery 69, the other terminal of which is connected to ground. Current flow over this circuit will cause relay 66 to operate and thereby complete a circuit from ground, the right hand armature T3 of relay 8G, conductor 19, right hand lever and normal contact of key 14, lamp 89, battery 8| and through ground to armature 18, whereby lamp 811 is lighted to indicate that a signal current is being received. At a station in which a line of the network terminates, only two relays, corresponding to relays 64 and 66, and two signal lamps, corresponding to lamps l5 and 80, will be used.

As a result of the propagation of the control currents over the lines of the network, all alternating current repeaters will be controlled to repeat signal currents in but one direction, 1. e., over the lower pair of conductors of the west line, upper pair of conductors of the east line and over a corresponding pair of conductors of each north line, and the unused conductors, i. e., those provided for east transmission in the west line, for west transmission in the east line and for south transmission in the north lines, will be short circuited. Short circuiting of the unused conductors serves to prevent undesired currents, produced in them by extraneous sources, and commonly referred to as noise currents, from affecting the useful currents transmitted through the pair of conductors being used for signal transmission.

The attendant at the station local to the splitting station, having his microphone connected to the outgoing conductors 21 of his loop circuit by virtue of the operation of his key l8 or 34, as described above, may broadcast over the network that he is about to transmit a picture. This broadcast is received by means of loud-speakers LS, which are permanently connected to the receiving conductors [S at the respective stations. At the splitting station, a loud-speaker is connected to each receiving loop circuit, i. e. to conductors l9 and 35. While detail instructions regarding the picture transmission to be effected may be broadcast, the system is designed to permit use of the network as a two-way circuit over which telephone conversations may be carried on for the transmission of traffic information.

If the network is to be used for two-way telephony, the attendant at the local station, as well as those at the stations which are to receive the picture, throw keys 1 8 to the right or talking positions. Operation of key I 8 at the local station from its left hand, or speech broadcasting position, to its right hand, or talking position, causes the right hand lever contacts of this key to be disengaged from the associated alternate contacts, whereby the telephone transmitter is disconnected from the outgoing circuit of the loop Li and ground is removed from conductor 31, with the result that the control circuit is broken, whereby the direct current and associated alternating current repeaters of the terminal loops and the network are all restored to normal, and the network is in a condition to be used for two-way telephone transmission.

With key 88 in the right hand, or talking position, the left-hand lever contacts are respectively caused to disengage the associated normal contacts and to engage their alternate contacts. The two lower left hand lever contacts of this key thereby connect the telephone transmitter, via conductors 29, to the primary winding of the lower repeating coil i6, and the receiver is connected through conductors 2 I and the upper alternate and lever contacts and conductors I1, to the primary winding of the upper repeating coil 55. Coils it are respectively connected by conductors 2i and 15, the upper and lower repeating coils and the upper and lower transmission paths of the alternating current repeater l 3 to the cable bridge i and via circuit connections provided therein through the respective outgoing and incoming paths over the lines of the network to the desired connected stations. The attendants at the stations having completed the telephone conversation, restore keys 18 to normal; thereby disconnecting their telephone sets from the incoming and outgoing paths of their respective loop terminal circuits and connecting conductors i9 and 25 thereto, and hence, associating the picture receiving and sending machines, with the respective paths.

Let it be assumed that a picture is to be transmitted to all stations or to certain stations associated with all of the lines. As herein shown, the connections between the local station and central oiiice are such that terminal loop L1 is used for transmission over all lines. However, terminal loop L2 could be used for this purpose if desired. The local sending apparatus and the receiving apparatus at the respective receiving station having been made ready, the attendant at the local sending station operates his starting key ":6 to apply ground to conductor 31 over the following circuit: from ground through key 16, left hand lever and normal contact of key 24, conductor 1i, relay 6 1, left hand armature of relay 68, battery and through ground to the point of beginning. Current flowing through this circuit causes relay E6 to operate to apply ground, via conductor 62, upper normal and lever contacts at the left of key Hi, to the conductor 31. Grounding this conductor causes the direct current repeaters, along the lines comprising the network, to operate as described above in con nection with the conditioning of the network for broadcasting speech. That is, all alternating current repeaters are conditioned for one-way transmission, and their output leads for the oppositely directed transmissions are short circuited. The system is therefore conditioned to permit a picture to be broadcast over the network.

Operation of relay 64 completes a second circuit from ground through its armature 12, conductor 13, inner left hand contact lever of key 14 and its associated normal contact, lamp 15, battery 16 and through ground to the point of beginning. Lamp 15 lights to indicate that a picture is being transmitted from the local station in all directions through the central office.

Picture current, which preferably is a picture modulated carrier current produced by scanning a picture to be transmitted with a beam of light modulated at a carrier frequency rate, which is definitely related to the rate at which the picture is scanned and utilizing the resultant doubly modulated light to activate a light sensitive electric device, is transmitted over conductors 23, lever contacts and associated normal left hand and middle contacts of key 24, conductors 25, the two lower normal and lever contacts at the right of key I 8, conductors 26 and the two lower normal and lever contacts at the left of key 18, windings of the lower repeating coil 66, conductors 21, the upper windings of repeating coil M, upper transmitting path of the alternating current repeater l3, conductors 28, connecting circuit of bridge A, lower transmission path of alternating current repeater 3, repeating coil of the coupling unit it and line to western stations, and through a connecting circuit of bridge 3 via upper transmitting path of alternating current repeater 5, connecting circuit of bridge 6, upper transmitting path of alternating current repeater 1, repeating coil and composite set 8 to the eastern stations. The picture current is also transmitted via a connecting circuit of bridge 4 to one circuit of line N1 and through a connecting circuit of bridge 6 to one circuit of line N2, which lines are provided with repeaters, composite sets and repeating coils, respectively, similar to 3, i and ii.

If a picture current, transmitted from a remote station over all lines, is to be received at the local station, terminal loop Li will be used, although terminal loop L2 could be used equally well by operating keys 24 to connect conductors 35 to the receiving machine. In the first case, i. e., using loop Li, the control circuit will have been rendered effective by the operation of the starting switch at the sending station to condition the lines of the network and the terminal loop for reception, with the result that the outgoing path of the repeaters of all lines including repeaters 3, i3, 1, 3i and those associated with lines N1 and N2 will be short circuited, key 18 will be in normal position and conductors l5 will be connected by the upper repeating coil E6 to the receiving machine R over the following circuit: the two upper lever and normal contacts at the left of key [3, conductors it, normal and lever contacts of key 25 and conductors 11 to the machine R.

The direct current repeater of loop L1 controlled by the operation of starting key at the remote sending station will operate relay 63 to apply ground to conductor 38, thereby completing the following circuit: from ground, conductors 38, 21, 31, upper right-hand lever and normal contact at the left of key i8, conductor 62, armature 63, conductor 65, winding of relay 66,

conductor 61, upper repeating coil l6, conductors l5 and 63, battery 69, its grounded terminal and through ground to the point of beginning. The relay 6% will operate to open the circuit through its left hand armature to the battery and to complete the following circuit through its right hand armature i8: from ground through armature l8, conductor 19, right hand normal and lever contacts of key M, lamp 86, battery 8i to ground and therethrough to the point of beginning, whereby lamp 8!! is lighted to indicate that signal currents, transmitted from some remote station to all lines, are being received.

If the network is to be split at the central office so that western and eastern sections may be provided for independent operation, the local attendant operates key 14. When this is done, the outer left hand key lever engages its alternate contact to complete the following circuit: from ground, through this outer key lever and alternate contact, conductor L, relay 82, resistance 83, battery 84 and through ground to the point of beginning. Relay 82 operates to pull up its armatures. The outer left hand armature 85 short circuits the lower transmission path of the alternating current repeater 5, the right hand armature 85 short circuits the upper transmission path of alternating current repeater 5 and the inner left hand armature opens the control circuit, thereby rendering both the alternating current, direct current and control circuits of the two sections independent of each other.

Bridges

4 and 6 are so designed that when

armatures

85 and 86 operate to short circuit the respective output paths of repeater 5, the transmission paths of other lines respectively interconnected thereby are not appreciably affected. This applies, however, to the situation where a bridge of the second type referred to in the above mentioned Green patent is used, i. e., in which the attenuators are given, by way of example, as comprising resistance of 5545 ohms in each side of the lines. While this value of resistances is used under certain given operation conditions, other values may be used.

In case bridges 4 and 6 comprise attenuators including resistances of low value in each side of the line, i. e., as set forth for the first example referred to in the above mentioned Green patent, the output paths of repeater 5 can not be directly short circuited without affecting the transmission paths of other lines respectively interconnected by the bridges. To avoid this and at the same time to permit splitting the circuit, short circuits are applied to the outputs of repeater 5 and resistances substantially equal to the impedance of the output paths of repeater 5 are connected between the short circuit and the bridges when relay 82 operates. This is shown in Fig. 4 to be described later.

Where bridges and 6 include resistances in each side of the line and of the higher order mentioned above, the short circuits are applied between the output circuits of repeaters 3, 1, l3

and 3! and the bridges, with which they are respectively associated, in order to prevent the detrimental effect of extraneous currents. However, where the bridges 5 and 6 include resistances in each side of the line which are of the lower order given in the first example of the Green patent, these short circuits are applied to the same side of each line but to the input circuits of repeaters 3, l i3 and 3!. This prevents the short circuits from affecting the other transmission pathsrespectively interconnected by the bridges.

If a picture transmission is to be effected over the east section, loops L2 are used. Key 24 is operated to cause its lever elements to engage with its alternate contacts, thereby disconnecting conductors 23 from conductors 25 and connecting them to conductors 36 and disconnecting the starting key lead from conductor H and connecting it to conductor 81. Keys and 34 being in their normal positions, operation of the starting key 70 applies ground to the circuit, including conductor 8?, relay 88, right hand armature 89 of relay 9!), battery. and through ground to key it]. Current flowing through this circuit operates relay 88 to apply ground through its right hand armature, conductor 9! and upper normal and lever contacts of key 34, conductor 51 to the right-hand winding of lower repeating coil 33, conductors 92, the upper winding of repeating coil 32, and conductor 99 to direct current repeater 58, which operates in the same manner as the direct current repeater associated with loop L1, to control the direct current repeaters associated with the lines included in the eastern section, i. e., east and N2 lines, to condition the latter for picture transmission thereover. At the same time the left hand armature of relay 88 completes a circuit from ground through this armature, conductor 94, lamp 95, battery 16 and ground, and lamp 95 is operated to indicate picture transmission from the local station to the eastern section. The path of the picture current is via conductors 23, the two left hand lever and alternate contacts of key 2d, conductors 36, two lower left hand normal contacts and lever contacts of key 34, conductors 25a, two lower right hand normal and lever contacts of key 34, lower repeating coil 33, conductors 92, upper repeating coil 32, upper transmission path of repeater 3|, and through connections of bridge 6 to lines E and N2. When transmission of the picture is completed, start key H1 is released to restore the apparatus units of the section to normal, whereby this section is made ready for the transmission of another picture.

A picture may be received from a station connected to the east section by operating key 2!] to connect conductors H to con-ductors 35. When the starting key at the remote sending station is .operated, the control circuit becomes efiective to control the apparatus units on the lines to energize a relay of the direct current repeater 53 which corresponds to relay of the direct current repeater associated with loops L1. Operation of this relay causes ground to be applied to the following circuit: conductors 99, 92, 51, upper lever and normal contacts of key 34, conductor 9!, right hand armature of relay 88, conductor 96, relay 9D, conductor 91, right-hand winding of upper repeating coil 33, conductors 98, right-hand winding of lower repeating coil 32, conductor 93 and a battery, included in direct current repeater 58, corresponding to battery 69 of the direct current repeater associated with loop L1; whereby the relay 90 is operated to pull up its armatures. Armature 39 disconnects battery from the circuit including relay 38, which controls the circuit through local sending key and lamp 95, and its left hand armature MB completes the following circuit: from ground through this armature, lamp IBI, battery 8! and ground to armature I00. Lamp I Si is thereby lighted to indicate that a picture is being received from some station of the eastern section. The picture current is transmitted from bridge 6 via conductors 30, lower transmission path of repeater 3|, lower repeating coil 32, conductors 98, upper repeating coil 33, the two upper right hand lever and normal contacts of key 34, conductors 35, alternate contacts and key levers of key 20, conductors TI to the receiving machine R.

When reception of the picture has been completed, the start switch at the sender of the remote eastern station is opened to break the control circuit, and the apparatus units of this section are restored to normal.

For picture operation over the western section, the transmitting key 24 and the receiving key 20 are restored to their normal positions to disconnect the sending and receiving machines from the eastern section and connect them to the western section. Picture transmission and reception over the western section are effected in the manner described above for transmission over the entire network.

Keeping in mind that the splitting key M has been operated and hence that its key levers engage their alternate contacts, a circuit is completed through the lamp I02 under control of relay 64 when key I0 is operated to start transmission of a picture over the western section. This circuit is as follows: from ground through key Ill, right-hand lever and normal contacts of key 24, conductor 'II relay 64, left hand armature of relay 66, battery and through ground to key I0. Relay 64 operates to apply ground through its left hand armature 63 to conductor 31 for conditioning the circuits of loop L1 and western lines W and N1, and by its right hand armature 12 to complete a circuit from ground, armature I2, conductor I3, middle lever and alternate con tact of key I4, lamp I02, battery I6 and through ground to armature I2.

When a picture is being received from the Western section, with the splitting key I4 operated, relay 66 is energized by the operation of the starting key II! at the transmitting station, in a manner similar to that described above in connection with reception from any station associated with the complete network. This serves to complete a circuit through lamp I03 over the following circuit: from ground, the right hand armature I8 of relay 66, conductor 19, left hand lever and alternate contact of key I4, lamp I03, battery 8I and via ground to the point of beginning.

While sending a picture to the western section, key 29 may be operated to connect the receiving machine to the eastern section, whereby a picture may be received from a remote station of this section. Again key 29 may occupy its normal, i. e., non-operated position to connect the receiving machine to the western section and key 24 may be actuated. In this case, the sending machine will be connected to send a picture to the eastern section, and the receiving machine will be connected for picture reception from the western section.

While the splitting arrangement has been described as applied to four-wire cable circuits, it may be used at a station for interconnecting four-wire cable lines with four-wire open-wire lines, or at a station where either type of fourwire lines is connected with two-wire open-wire lines.

For two-wire open-wire line connection, the circuit shown in Fig. 3 may be substituted for that included between bridge 4 or t and all lines interconnected by these bridges. In other words,

it may be used in place of the arrangement shown in some detail at the right and left, respectively, of section lines XX, Fig. 1.

The circuit of Fig. 3 will be hereinafter described, by Way of example, as a substitute for the circuit shown between section line XX and the east line. Leads I I9 and III correspond to 'the output and input leads, respectively, of the bridge circuit 6 and repeater II2 corresponds to the repeater I. The output or sending leads, i. e., the upper transmission path of the repeater, are normally connected by leads II 3 and M3 to the input terminals of a filter H5, the output terminals of which are connected by leads H5 and II! to outside winding II8 of a three-winding transformer, the middle windings H9 of this transformer have their terminals respectively connected through a repeating coil and composite set to the east line I20 and to the balancing network N and mid-taps of winding use are connected to the input leads of repeater I i2, 1. e., the lower transmission path of the repeater. The two-wire line is. thereby conjugately related to the four-wire output circuit of the repeater H2. The input leads for the repeater II2 include a resistance pad I2I.

Associated with this terminal apparatus is a direct current repeater provided with a connection to the control circuit lead 46. When this lead is grounded by the operation of the direct current repeater associated with terminal loop L1 or L2 of the local station or direct current repeater as of the west line, due to the talking key being thrown to the broadcast position or to the starting key for the picture sending machine having been closed to operate relay 3! of the loop circuit direct current repeater or relay 55 of repeater M, current flows from ground at the direct current repeater of the two-wire teminal, battery I22 through relay I23, relay I24, conductor I25, armature of polarized relay I25, conductor I2? which extends to lead 46 of Fig. 1 through the armature of relay 56 of direct current repeater 44 and armature 4| of relay 33 included in the direct current repeater associated with loops Ll and through ground to the grounded terminal of battery I22. Relay I53 operates to pull up its armature and thereby disconnects lower battery I28, which normally applies direct current of one sign to the lower conductor of the two-wire line I20 and connects upper battery I28 to supply direct current of opposite sign over the following circuit: from upper battery I28 through the armature of relay I23 and a composited connection over the line. Relay I24 operates through one armature I29 to apply ground to a circuit including the winding of slow-release relay i351 and battery, one terminal of which is grounded, and also through its armature I3I to complete a holding circuit for relay I26. Slow-release relay i 39 pulls up its armature to apply ground to a circuit including the winding of a relay E32 and battery I33, the other terminal of which is grounded. Relay I32 is thereby operated, its upper inner armature removes ground from the circuit I34, adapted to be controlled by relay I25 when this relay is operated by incoming direct current impulses received over the control circuit due to the operation of the start switch of a sending machine of a remote station of the eastern section, and by its upper outer armature to complete a relay circuit as follows: from ground through lead I35 to this armature, lead I36 to relays I31 and I38, associated with the input and output circuit of filter H5, and relay I39 asso- Cal ciated with the input or lower transmission path of repeater l 52. The winding of relay I31 is energized over the following circuit: from ground ME], battery Ml, winding of relay I31, conductor E38, upper armature of relay 132, lead I35 to ground and therethrough to M8. The winding of relay E38 is energized over the following circuit: from ground M2, battery M3, winding of relay i353, conductor E35, lead E35 and through ground to M2. These two relays operate through their upper armatures to connect lead H3 directly to lead M6 via conductor 4, and through their lower armatures to connect lead H4 directly to lead E El via conductor i 55, thereby removing filter l l 5 from the output circuit, 1. e., the upper transmission path of repeater H2. Relay 139 is energized from ground, battery I45, winding of relay I38, conductor 93%, lead E35 and through ground to battery M6, to pull up its armatures and thereby short circuit the input circuit, i. e., the lower transmission path of repeater H2. As in the case of the four-wire line, direct current repeaters associated with alternating current line repeaters will be operated by the reversal of direct current supplied to the line toefiect certain control functions at these repeaters, and the reversed direct current will operate to efiect like results at the successive alternating current station repeaters included in the lines comprising the eastern section, and hence the attendant at the local station, or an attendant at a station of the western section, may broadcast speech or send picture currents over the eastern section, depending upon whether his talking key has been set for broadcasting or his start key has been operated to transmit a picture.

In case two-way telephone conversations are to be effected from a local station or a station of the western section through the central office, no ground is applied to lead 45, and hence relays [31, 38 and we are not operated. Both paths through repeater M2 are operative and filter H5 is included in the output or upper transmission, path of this repeater. Filter H5 is provided to prevent singing when two-way repeating is effected through the four-wire two-wire termination connecting the repeater l l2 to the east lines, and the slow-release relay of the direct currentrepeater is provided to prevent irregular operation of the repeaters or terminating apparatus due to undesired current impulses produced in the control circuit. For a complete disclosure of the operation of the repeater described above, reference be made to R. B. Hearn Patent 2,018,494, issued October 22, 1935.

When the direct current repeater associated with the two-wire four-wire terminating circuit is in normal condition and a similar repeater associated with the line in question has been operated, either by throwing the talking key to the broadcasting position or closing start key of the picture machine at any remote eastern station, control impulses incoming via the composite connection to the upper conductor of the line section east of the terminating point, will flow through the winding of relay I125 to ground. These impulses being of opposite sign to those normally supplied over the upper conductor energize polarized relay 825 which pulls up its armature, thereby disengaging it from its normal contact to open the circuit or relays ms and I24 and causing it to engage its alternate contact, to apply ground over the inner lower armature of relay E32, conductors i236 and It? to conductor #6, whereby the direct current repeaters associated with the terminal loops L1 and L2 and the lines of the western section are controlled to condition them for broadcasting speech or for picture transmission. Under these conditions, broadcast speech or picture transmission is effected over the conjugate connection, path l2! and the lower transmission path of repeater I IE to the local station and to stations of the western section. While relays 53?, I38 and IE3 are not operated, the local station output paths and those of the other lines transmitting into the bridges are short circuited.

In case the western section consists of twowire open-wire lines, the direct current repeater M and those associated with other lines of this section would be replaced by a direct current repeater of the type described above for use with two-wire open-wire lines.

By operating splitting key M, the network of open-wire lines may be split at the central office and both sections may be independently operated as described above, in connection with the four-wire cable network.

A split-ting arrangement for use with openwire lines is shown in Fig. 4. This arrangemer. will be substituted for the central ofiice of Fig. l, i, e,, for that portion of the last mentioned figure between section lines Y-Y and ZZ with which are associated four-wire two-wire terminating circuits of the type disclosed in Fig. 3 to effect connection to the various lines W, E, N1 and N2.

Bridges

4 and 6 will comprise resistances in each side of the line which are of the lower order mentioned in the Green patent hereinbeiore referred to, and the respective input circuits or" repeater 5 will include resistances 25b and Hit. When the network is used as a complete entity, these resistances are short circuited by

armatures

85 and 86, respectively, of relay However. when the splitting key has been operated to apply ground to conductor L, as hereinbefore described, relay 82 will operate to pull its armatures. Armature 45 will open the control circuit 43, armature 85 will disengage its forward contact to open the short circuit around resistance I59 and engage its back contact to short circuit the connection between this resistance and the lower output path of repeater 5, and armature 85 will disengage its forward contact to open the short circuit around resistance 55 and engage its back contact to apply a short circuit to the connection of this resistance to the upper output path of repeater 5. Thus the low leads of bridge t and the upper leads of '5 are terminated in resistances the impedances of which should be substantially equal to the output impedances of the respective repeater paths of repeater 5 and, each section of the network may be operated independently of each other, in the manner described with respect to Fig. 1.

Operation of relay 528, included in the direct current repeaters of thctype shown in Fig. 3, which are associated with the different interconnected by the bridges, or of relay included in the direct current repeaters associated with the station loops L1 and L2, as hereinbefore described, will cause its armature to short circuit the input of repeater 3, as well as the inputs of repeater I and those associated with the lines.

By virtue of the use of this arrangement, the network may be split without materially afiecting the transmission paths of the lines interconnected by

bridges

4 and 6.

14-. Ail;

Bridge arrangements may be connected in series between bridge 4- and the west line or between bridge 6 and the east line to permit the use of additional lines radiating from the splitting station. One or more of these bridges may be associated with the western group or the eastern group or both groups. In the first two cases, when the network is split, either the west ern or eastern section will include a greater number of lines local to the splitting station than the other, whereas in the latter case the two sections will include the same number of local lines.

What is claimed is:

l. A communication system comprising a transmission network including a central ofiice, a series of lines terminating at said oiiice, a plurality of means for interconnecting said lines in groups, apparatus at said central office for connecting said plurality of interconnecting means together, means at a station local to said central office and at other stations connected to each line for supplying and receiving signal currents to and from said network, control means at any of said stations for conditioning said network for one-way transmission in either direction from one of said lines to said other lines, and means at said local station for controlling said connecting apparatus at said central office for splitting said network into a plurality of independently operable sections.

2. A communicating system comprising a transmission network including a central office, a series of lines terminating at said oiiice, a plurality of means for interconnecting said lines in groups, apparatus at said central office for connecting said plurality of interconnecting means together, a station local to said central ofiice, other stations connected to each of said lines, means at said local and each of said other stations, for supplying signal currents for twoway transmission over said network, means for conditioning said network for one-way signal transmission in either direction from one of said lines to said other lines, and means at said local station for controlling said connecting apparatus at said central ofiice for splitting said network into a plurality of independently operable sections.

3. A communicating system comprising a transmission network including a central office, a series of lines terminating at said ofiice, a plurality of means for interconnecting said lines in groups, apparatus at said central office for connecting said plurality of interconnecting means together, a station local to said central ofiice, other stations connected to each of said lines, two-way alternating current repeaters in each said lines, means at the local station and each of said other stations for supplying alternating signal currents for two-way transmission over said network, means including direct current repeaters, associated with each said alternating current repeaters, for conditioning said network for one-way alternating current signal trans mission in either direction from one of said lines to said other lines, means at said local station and each of said other stations for controlling said conditioning means, and means at said local station for controlling said connecting apparatus at said central office for splitting said network into two independently operable sections with either of which the apparatus of the local station may be associated.

4. A communicating system comprising a transmission network including a central ofiice, a

series of lines terminating at said ofiice, a plurality of means for interconnecting said lines in groups, apparatus at said central ofiice for connecting said plurality of interconnecting means together, a station local to said central office, other stations connected to each of said lines, two-way alternating current repeaters in each said lines, means at the local station and each said other stations for supplying alternating signal currents for two-way transmission over said network, means including direct current repeaters, associated with each said alternating current repeaters, for conditioning said network for oneway alternating current signal transmission in either direction from one of said lines to said other lines, means at said local and each of said other stations for controlling said conditioning means, means at said local station and each said other stations for supplying alternating signal currents for one-way transmission over said network, means at said local station for controlling said connecting apparatus at the central ofiice for splitting said network into independently operable sections, and control means at said local station for connecting signaling means thereat for simultaneous operation with the respective sections.

5. A communicating system comprising a transmission network including a central office, a series of lines terminating at said office, a plurality of means for interconnecting said lines in groups, apparatus at said central ofiice for connecting said plurality of interconnecting means together, a station local to said central ofiice, other stations connected to each of said lines, twoway alternating current repeaters in each said lines, means at the local station and each said other stations for supplying alternating signal currents for two-way transmission over said network, means including direct current repeaters, associated with each said alternating current repeaters, for conditioning said network for oneway alternating current signal transmission in either direction from one of said lines to said other lines, means at said local and each of said other stations for controlling said conditioning means, means at said local station and each said other stations for supplying alternating signal currents for oneway transmission over said network, means at said local station for controlling said connecting apparatus at the central oflice for splitting said network into independently operable sections, and control means at said local station for connecting signal transmitting means to one section and signal receiving means to the other section.

6. A communicating system comprising a transmission network including a central ofiice, a series of lines terminating at said office, a plurality of means for interconnecting said lines in groups, apparatus at said central ofiice for connecting said plurality of interconnecting means together, a station local to said central oifice, other stations connected to each of said lines, two-way alternating current repeaters in each said lines, means at the local station and each said other stations for supplying alternating signal currents for two-way transmission over said network, means including direct current repeaters, associated with each said alternating current repeaters, for conditioning said network for one-way alternating current signal transmission in either direction from one of said lines to said other lines, means at each of said local and other stations for controlling said conditionlng means, means at said local station and each said other stations for supplying alternating sig nal currents for one-way transmission over said network, means at said local station for controlling said connecting apparatus at the central office for splitting said network into independently operable sections, and control means at said local station for connecting signal transmitting means to either section and signal receiving means to the other section.

'7. A communication system comprising a transmission network including a central oflice, a series of lines terminating at said office, a plu rality of means for interconnecting said lines in groups, apparatus at said central office for connecting said plurality of interconnecting means together, means at a station local to said central office and at other stations. connected to each line for supplying and receiving signal currents to and from said network, and means at said central ofiice for conditioning the network for one-way transmission thereover, controllable from each station.

8. A communication system comprising a transmission network including a central oflice, a series of lines terminating at said office, a plurality of means for interconnecting said lines in groups, apparatus at said central office for connecting said plurality of interconnecting means together, means at a station local to said central oflice and at other stations connected to each line for supplying and receiving signal currents to and from said network, including devices for respectively repeating alternating signal currents in opposite directions with respect to said central oflice, and means at said central office for short circuiting the device in the transmission path opposite to the direction of alternating current signal transmission, controllable from each station.

9. A communication system including a series of lines terminating in a central ofiice comprising a plurality of means respectively connecting a plurality of said lines in a group, apparatus connecting said plurality of means together and means associated therewith for rendering said connecting apparatus inoperative, and a station local to said central office including means for controlling the means associated with said connecting apparatus at the central oifice.

10. A communication system including a series of lines terminating in a central ofiice comprising a plurality of means respectively including conductive paths interconnecting a plurality of said lines, apparatus connecting said plurality of means together and means associated therewith for rendering said connecting apparatus inoperative, and a station local to said central office including means for controlling the means associated with said connecting apparatus at the central oifice.

11. A communication network comprising a series of lines terminating in a central office having a plurality of means respectively connecting a plurality of said lines, apparatus including a plurality of conductive paths connecting said plurality of means together and means for short-circuiting the respective conductive paths, and a station local to said central office comprising means for controlling said short-circuiting means.

12. A communication network comprising a series of lines terminating in a central oflice having a plurality of means respectively connecting a plurality of said lines, apparatus including a plurality of conductive paths connecting said plurality of means together and means for shortcircuiting the respective paths through a terminating impedance, and a station local to said central oflice comprising means for controlling said short-circuiting means.

13. A communication system comprising a transmission network having a series of lines terminating in a central office which comprises a plurality of means respectively connecting a plurality of said lines in a group, apparatus connecting said plurality of means together, and means ciated therewith for rendering said connectpparatus inoperative to thereby split the netinto sections, and a station local to said central oflice comprising means for actuating the splitting means at the central ofiice, means for sending receiving signals, and means for connecting said signal sending and receiving means to the respective sections.

M. A communication system comprising a transmission network including a series of lines terminating in a central office, comprising a plurality of means respectively connecting a plurality of said lines in a group, apparatus connecting said plurality of means together, and means associated therewith for rendering said connecting apparatus inoperative to thereby split the network into sections, and a station local to said central office including means for actuating the splitting means at the central office, means for sending and receiving signals, and means for connecting signaling means to either of said sections.

15. A communication system comprising a transmission network including a central oifice provided with a plurality of means for interconnecting a series of lines terminating therein, apparatus for connecting said plurality of interconnecting means together, and means for controlling said connecting apparatus to split said network into a plurality of independently operable sections, and a station local to said central ofiice comprising means for actuating the splitting means at said central office, signal sending means, and means for connecting the signal sending means to either of said sections.

16. A communication system comprising a transmission network including a central office provided with a plurality of means for interconnecting a series of lines terminating therein, apparatus for connecting said plurality of interconnecting means together, and means for controlling said connecting apparatus to split said network into a plurality of independently operable sections, and a station local to said central office comprising means for actuating the splitting means at said central office, signal receiving means, and means for connecting said signal receiving means to either of said sections.

17. A communication system comprising a transmission network including a central ofiice provided with a plurality of means for interconnecting a series of lines terminating therein, apparatus for connecting said plurality of interconnecting means together, and means for controlling said connecting apparatus to split said network into a plurality of independently operable sections, and a station local to said central onice comprising means for actuating the splitting means at said central office, signal sending and receiving means, and means for simultaneously connecting one of said signalling means to one section and the other of said signalling means to the other section.

18. A communication system comprising a transmission network including a central oifice provided with a plurality of means for interconnecting a series of lines terminating therein, apparatus for connecting said plurality of interconnecting means together, and means for controlling said connecting apparatus to split said network into a plurality of independently operable sections, and a station local to said central oilice comprising means for actuating the splitting means at said central office, signal sending and receiving means, and means for simultaneously connecting said signal sending and said receiving means to the respective sections one at a time.

19. A communication system comprising a transmission network including a central ofiice provided with a plurality of means for interconnecting a series of lines terminating therein, apparatus for connecting said plurality of interconnecting means together, and means for controlling said connecting apparatus to split said network into a plurality of independently operable sections, and a station local to said central office comprising means for actuating the splitting means at said central office, means for sending and receiving signals of different types to and from said sections and means for connecting the means for sending and receiving signals of one type to either one of said sections or for simultaneously connecting such means to the respective sections, or, alternatively, for connecting the means for sending signals of another type to either one of said sections and for connecting the means for receiving signals of this type to another section.

20. A communication system comprising a transmission network including a central oflice provided with a plurality of means for interconnecting a series of lines terminating therein, apparatus for connecting said plurality of interconnecting means together, and means for controlling said connecting apparatus to split said network into a plurality of independently operable sections, and a station local to said central office comprising means for actuating the splitting means at said central oifice, signal sending and receiving means, switching means connecting the means for sending and receiving signals of one type to either of said sections or for simultaneously connecting such means to the respective sections, or, alternatively, for connecting means for sending signals of another type to either one of said sections and for connecting means for receiving signals of this type to another section.

21. A communication system comprising a transmission network including a central oflice provided with a plurality of means for interconnecting a series of lines terminating therein, apparatus for connecting said plurality of interconnecting means together, and means for controlling said connecting apparatus to split said network into a plurality of independently operable sections, and a station local to said central ofiice comprising means for actuating the splitting means at said central office, signal sending and receiving means, a plurality of switching means including switches for connecting the means for sending and receiving signals of one type to either one of said sections or simultaneously for connecting means for sending and receiving signals of this type to the respective sections, and other switches, cooperating with said first named switches, for connecting means for sending signals of another type to either one of said sections and for connecting means for receiving signals of this type to another section.

22. A communication system comprising a transmission network including a central oflice provided with a plurality of means for interconnecting a series of lines terminating therein, apparatus for connecting said plurality of interconnecting means together, and means for controlling said connecting apparatus to split said network into a plurality of independently operable sections, and a station local to said central oflice comprising means for actuating the splitting means at said central office, telephone apparatus, picture sending and receiving devices, and means for connecting telephone apparatus to either or both sections, or, alternatively, for connecting the picture sending device or the picture receiving device to either of the sections or simultaneously to respective sections.

ELLIOT M. STAPLES.