US1382631A - Repeater-circuits - Google Patents

Description

Q S. DEMAREST AND S. P. SHACKLETUM H'EPEATER CIRCUITS.

APPLICATION FILED MAYH. 1919.

1 382 310 mum J6 28,1921.

2 SHEETS SHEET i- ATTORNEY UNITED STATES PATENT OFFICE.

' "CHARLES s. nEnAREsr, or BROOKLYN, AND SAMUEL r. SHACKLET'ON, on NEW YORK, 'n. Y., 'Assronons r AMERICAN TELEPHONE AND TELEGRAPH COM- rm, A CORPORATION or NEW YORK. I

Specification of Letters Patent.

REPEATER-CIRGUITS.

Patented June 28, 1921.

Application filed May 17, 1919. Serial 1 10. 297,902;

x T 0 all whom it may concern:

, Be it known that we, CHARLES S.DE1\IAREST and SAMUEL P. SHACKLETON, residing at Brooklyn and New York, in the counties of Kings and Bronx and State of New York, respectivel have invented certain Improvements in T?epeater-Circuits, of which the following is a specification.

This invention relates to transmission circuits and more particularly to transmission circuits in which repeatersare employed.

One of the objects of this invention is to simplify the apparatus and reduce the expense connected with the installation of repeater equipment for telephone lines. Another object of the invention has reference to the provision of means whereby one repeater may be employed for a plurality of connecting circuits. Other and further ob jects of the invention will more fully appear in connection with the detailed description hereinafter given. I

Where cord circuit repeaters are employed in the establishing of connections between long distance transmission lines, it is customary to provide a repeater unit for each repeater cord at each position. Under certain circumstances, however, it is desirable that the same operating unit be used for repeater cords at two positions so that the. amount of apparatus necessary may be reduced. The repeater unit comprising the amplifiers, relays, coils, etc., is usually arranged at a point some distance from the switchboard and is connected with the switching cords and controlling keys such as the listening, splitting and repeater control keys by means of a series of conductors extending from the repeater unit to the switchboard position. These conductors are of two kinds, those used for transmission purposes and extending to theplugs or other switch ing arrangements of the cords, and those used merely for control or supervisory purposes, and leading to the several controlling keys. In accordance with the present invention the apparatus is so arranged that the controlling conductors leading from the repeater unit'may be switched into connection with conductors leading, to the controlling keys at either of two switchboard positions. The transmission conductors leading to the plugsor other switching means at-the switchboard positions are connected in parallel to the two positions. Means are switching plugs at both positions. By this arrangement of the apparatus the operator who first establishes a connection has complete control over the repeater and while it is possible for the operator at the other position to attempt to set up a connection, substantially no harm can result therefrom since the operator cannot by means of the controlling keys interfere with the connec tion already established and cannot by means of her listening set obtain access to the connection which she attempted to es tablish. The association of additional lines with the lines already connected does not result in unbalancing the repeater and caus: ing singing for the reason that artificial lines are associated with the circuit at the same time. In order, however, to prevent the possibility of an operator attempting to set up an additional connection of this char? acter a busy lamp is caused to glow at the other switchboard position when the first connection is established in order to indicate that the repeater is already in use.

The invention may now be more fully un derstood by reference to the following description when read in connection with the accompanying drawings, Figures 1 and 2 of which constitute a circuit diagram of one embodiment of the invention.

Referring to the drawing, a repeater organization of the well known two-way two repeater type including amplifiers A and-A is illustrated. This repeater be associated with either of two switchboard positions designatedas X and Y upon the drawing. In order to interconnect toll lines through the repeater, the operator at posie tion X is provided with cords terminating in twin plugs P, and 1?, adapted to cooperate with twin jacks of toll lines. In a similar manner the operator at position Y is provided with cords terminating in plugs P, and P In order that the repeater shown in Fig. 2 may be used in establishing connections at either switchboard position, the incoming line conductors L and the corresponding artificial line conductors N of the repeater are connected in parallel over conductors L and L and conductors N and N to the incoming twin plugs P and P at the two positions. In a similar manner-the outgoing conductors L and N are connected in parallel over conductors L and L and over conductors N and N to the out oing twin plugs P and P ormally the repeater is not included in circuit with the incoming and outgoing conducto'rs leading to the switching plugs at either position to the inconiing' line. Gonductors L are connected to thefline conductors L through a direct connection including conduc'torsC and The conductors and C nia'y ibe interconnected either through conductors C C and the contaetsof the Splitting key K at position X orithrough conductors Ci and G and the ont'actsof the splitting'key K at position In order to exercise control over the connec'tions which may be "established at position Xthroughthe rpeaterfthe operatorat thatjgiosition is provided with a listening key anda repeater control key K 1n ad'- ditinnfto the splitting "key K already freferret'i to. In a simila'r'manner'the operator at position Y is provided with 'lis'teningkey 'Ki and repeater control key K in addition to the splitting 'lrey K The various control circuits which will be hereinafter described as "eirtending from the repeater to the several 'keys at'each operators position are arranged to pass over the contacts of a series ofswitching relays 1,2 and '3. Norinally the cdrd circuit conductors "C and C aswellas the control circuit conductors are extended 'over the back contacts of these switching relays to the keys K K and K at position When the switching relays are energized howeverjthe cord circuit connections as well as the controlling circuit connectionsiare'shifted from the keys at .po- "sition 'X to the corresponding 'keysat position Y. I v

In order to effect the switching 'of these circuits by means of the switching 'rela'ysa double wound relay 4 is provided in the sleeveicirciiitsof the plugs 'P and'P at position Y so that when" either orboth o'f'these plugs are inserted in line jacks therelay 4 will be energized to efi'ectthe shifting of the connections. A similarrelay 5 is provided in the sleeve circuits of the plugs P and P at position X. The circuit of the relay 5 is rendered inoperative when the relay 4 is energized. In a similar manner when the relay 5. is energized by inserting either or both of plugs P and P in line jacks, the circuit of the relay 4 is rendered inoperative so that the switching relays 1 to 3 inclusive will remain in their normal condition with the cord conductors and controlling circuits switched to position X.

The transmission connections extending from the repeater 'to the line and artificial line contactsof the plugs at "the two positions in parallel are at no time affected by the transfer of the circuit control from one position to the other. This avoids transmission losses which might result from the additional relay contacts which would have 'to be provided in these transmission connections if they were to be shifted from one position to the other.

In order to prevent any possibility o'fc'onfusion arising from one operator "at one posiition attempting to set up a connect-ion when the repeater is already em loyed a connectionset up at the other position, busy IampsG and 7 are provided forthe two positions so that whenacon nection is established at one position the busy lamp at the other position will be caused to glowfindicating to the operator at that position that the apparatus is already in use.

Should the operator a't-o'ne position ignore the busy lamp and insert the plugs in the jacks of'toll lines, no harm would result so f'ar'as the repeater iscon'c'erned even though the two connections were crossed since the operator upon insertin the'twih plug'in the jack connects-a suitable balancing network to the repeater at the same time that the toll line is connected to the repeater consequently even though two linesbe connected in parallel 'to "each end of the repeater, *the repeater will still remain balanced andsinging will'not'result. 7

By placing the controlling circuits under the control of the operatorwho first established the connection, the second operator will beunableto interfere with-thecon'ne'c tion established by the first o eratorsy manipulating any o'f her controlling keys and Assuming that theoperator at-position desires to setup connection "betw'een two to'll lineslthro'ugh the repeater shown in Fig.2, the plug P will 'be inserted in the j'ackj of the incoming line thereby completing a'circuit from the grounded sleeve contacts "of said jack over "sleeve contactsof the plug P through the left handwinding ofrel'aiy 5 and over the right'handback'contact ofr'elay 4 to battery. Aparallelcircuit'isestablished at the same timeoverthe groun'deli sleeve contacts of the jack, sleeve contacts of the plug P inner left hand back contact of relay 4 and over conductor 8 through the winding of relay 9 to battery.

Relay 5 upon being energized disconnects battery at its left hand contact from the windings of relay 4 thereby preventing the energization of said relay due to the operator at station -Y attempting to establish a connection through the plugs P and P Relay 5 at its left hand front contact completes a circuit from battery over conductor 10 and through the busy'lamp .7 to ground thereby causing the lamp to glow to indicate to the o erator at position Y that the repeater is a ready in service. Relay 5 by opening its right hand contacts disconnects the sleeve conductors of plugs P and P, from the sleeve relays 9 and 12. The switching relays 1, 2 and 3 are under the control of the relay 4 and as this relay has been rendered inoperative by the relay 5 the switching relays cannot be affected by any attempt of the operator at position Y to set up a connection.

Returning to relay 9 whose circuit was completed by inserting the plug P in the line jack, the energization of said relay results in the completion of a circuit from ground over the lower front contact of said relay to point 13 from which point the circuit extends over conductors 14 and 15,back contacts of ringing responsive relays 16 and 17 in series and over conductor 18 through the winding of relay 19 to battery. Relay 19 is energized over the circuit above described and by opening its right hand contact prevents the energization of relay 20 which would otherwise result from the connection of ground to the point 13.

A direct connection now extends between the line contacts of plugs P and P over conductors L and 11, back contacts of relay 21, conductors C, back contacts of relay 3, conductors C normal right hand contacts of splitting key K conductors 22, normal left hand contacts of splitting key K conductors C back contacts of relay 2, conductors C, back contacts of relay 23 and over conductors L and L to plug P The operator by actuating the listening key K, may bridgeher set across the transmission path above traced at points 24 and 25.

In order to complete the connection to the outgoing transmission line, the operator may insert the plug P in the jack of the outgoing transmission line and operate the repeater control key K,. A circuit is completed from the grounded sleeve contacts of the outgoing line iack over the sleeve contacts of the plug P through the right hand winding of relay 5 and over the right hand contact of relay 4 to battery. This circuit is without effect as relay 5 had already been energized through its left hand winding. A parallel circuit is completed over the sleeve contacts of plug]? over the left hand contact of relay 4 and through the winding of relay 12 to battery. Relay 12 is therefore energized andat its lower contact connects ground to point 13 in par allel with the ground connected over the contact of relay 9. The actuation of the re peater control key K completes a circuit for the filament control relay 29 from battery through the winding of said relay over conductor 30, right hand back contact of relay 3 over conductor 31, right hand make contact of key K over conductors 32, 3 3 and 14 to point 13 and thence to. ground over the lower front contacts of relays 9 and 12. The energization of relay 29 over the circuit above traced results in the completion of the filament circuit from battery B through the filaments of the amplifiers A and A rendering the tubes operative.

The actuation of the repeater control key K also results in completing a circuit from grounded point 13, over conductor 34, right hand back contact of relay 1, conductors 35 and 36, also normal right hand and left hand contacts of splitting key K ri ht hand normal contact of listening key k conductor 37, inner left hand back contact of relay 1, conductor 38,-upper front contacts of relays 9 and 12,' conductors 39 and 40, left'hand make contact of key K conductors 41, 42 and 43 through the winding of relay 44, back contact of relay 45 over conductor 46 and thence in parallel through the windings or relays 21 and 23 to battery. Relays 44, 21 and 23 are energized over the circuit above traced, the former operating to open the short circuit normally existing about the primaries of input transformers 47 and 48 of the repeater and to connect said transformers to input bridges 49 and 50 of the repeater. Relays 21 and 23 operate to disconnect the line conductors L and L from the cord conductors U and C and to connect the repeater in circuit.

With the circuit in the condition just described, transmission from the incoming line passes over conductors L and L over the front contacts of relay 21, through the input bridge 49 and input transformer 47 through the amplifier A, where the variations are amplified, to the output circuit 53 and transformer 52. At the transformer the energy divides, part flowing to the outgoing line over the front contacts of relay 23 and conductors L and L and part flowing to the artificial line over conductors N and N In a similar manner transmission from the outgoing line passes over conductors L and L over the front contacts ofrelay 23 to the input bridge 50 and input transformer 48 through the amplifier A to the output circuit 54 and output transformer 51 where the energy divides, part flowing over the front contacts of relay 21 and conductors L anclL to the incoming line and part flowing over conductors N and N to the artificial line. I

If, with the circuit in this condition, ringing current should be transmitted from the incoming line, the ringing current will flow over'conductors L and L to ringin responsive relay 17 which will be actuate to open the circuit previously traced through relay 19. Relay 19 is accordingly deenergized and completes a circuit from :gr-oundedfipoint 13 over the back contact of relay 19 and through the Winding of relay 20 to battery. Relay'20 at its right hand'front contact completes a circuit for relay '45 which-may be traced from grounded point -13'over conductor 34, right hand back contact of relay 1, conductors 35 an'd36 lower normal contacts of the splitting key k right hand normal contactof listenin key K conductor 37, inner left hand bac contact-' of relay 1, conductor'38, upper front contacts of relays 9and 12, conductors 39- and 40, left hand make contact of key K conductors 4'1, 42 and 55, front right hand contact of relay20 and through the winding of relay 45 to battery. Relay 45 upon being energized opens the circuit previously traced through relays 44, 21 and 23 and atits-front contact com'pletes a holding circuit for relays 21 and 23 from ground over conductor-46 and through the windings of said relays to battery. Relay 44 is deenergized and again short circuits the input windings of the transformers 47 and 48 to prevent ringingcurrent from being transmitted to the repeater.

Returning to relay 20, saidrelay at its left hand front contact completes a circuit from grounded point;13 over the left hand front contact of relay 20 through the winding of relay '56 to battery. Relay '56 completes a locking circuit over its upper frontcontact over conductors 57 and 58, left hand normal contact of key K conductors 59 and 35, right hand back contact of relay 1 to grounded point 13. At its lower front contact relay 56 completes a circuit'fromg'round over conductor 60, left hand back contact of relay 1 and through the lamp 61 tobattery. The lamp '61 now glows to indicate tothe operator that a ring has'come in from one of the toll line's.

The operator may now actuate the listenink key K which, by opening'its left hand contact, breaks the locking circuit of relay 56 with the consequent eifacement of the lamp 61. Key K by openingits right hand contact breaks the circuit previously traced to relay 45 which is deenergizedand again connects relay 44 in circuit with relays 21 and 23. The original circuitof theserelays, however, it will be remembered, passes over the right hand contact of the'key K so that relays 21 and 23-are now denergized in addition to the relay 44. 'Thedeenergization of relays21 and 23-resultsin again interconnectingtheline conductors L'andL through the cord connection includingconductors C, 0, the splittingkey K and cOnd'uctOrS C and 0 .1 The'operators set is now. bridged across this circuit and the operator upon ascertaining that the iCELll came in from the incoming line may, ifishe desires, :throw, the splitting key K to the leftvthereby (llSCOII-r necting the outgoing end of thegc'ircuit so that her set will remainconnected 'tothe incoming line to the exclusion of the outgoing line. p

If, with the circuit in the condition just described, ringing current should be trans? mitted over the outgoing line, the tI'ELIISmlt-I ted ringingcurrent wouldjpass over conductors L and. L to the ringing-responsive relay 16 thereby again opening the circuit of the relay 19 which was, "of course,restored as-soon as relays? ceased to respond to ringing current. elay 19-again closes thecircuit of-relay 2O whicha ain completes the circuit of relay :56 but 1 oes not cause the energization of relay 45 gas the circuit of the latter relay is held open at the -con-. tacts of the listening and splitting keys. A locking circuit 'forrelay-56 is completed over the upper front contact ofsaid relay over conductors 57, 58 and 62, lower left hand make contact 1 of splitting key K lower right hand normal contact of said key over conductors 36 and 35, right hand back contact of relay 1 and-over conductor 34 to grounded point 13. Relay56 again completes -the'cir cuit of the lamp 61 whereuponthe operator is informed that a call has come in over the outgoing line.

The operator maythen throw the splitting key to the right thereby disconnecting the incoming line from the circuitandleaving her set bridged across the outgoing line. The actuation of the Splitting key momentarily opens the locking circuit above traced for relay 56 which is accordingl deene'rgized and effaces the lamp 61. S ould the operator restore the listening key K and the splitting key K to normal, the circuit originally traced for relays 44, 21 and 23 would be again completed so that the re-' peater is again rendered, operative and is connected in the transmission circuit.

Should the operator desire to take down the connection she will withdraw plugs P and R from the line jacks and restore the key K. to normal. The withdrawal of the plugs P and P breaks the circuits through both windings of relay 5 and through the relays 9 and 12 so that these relays are restored to normal. The lamp 7 is effaced bythe deenergization of relay 5 and battery is again connected to the windings of relay 4.. The deenergization of relays 9 and 12 removes the ground connection from point 13 so that relays 19, 29, 44, 21 and 23 are deenergized it being remembered that the circuits of all of these relays pass to ground through point 13. The apparatus is now in a normal condition and ready for the completlon of a connection at either position X or position Y.

It will be noticed with reference to the connection described as having been set up at the osition X, that the various circuits control ed by keys K K and K extended from the repeater to said keys over the back contacts of switching relays 1, 2, and 3. Alternative connections are provided to the keys K K and K, at position Y but these connections are inoperative since they are maintained open at the contact of the switching relays, 1, 2 and 3. The operator at position Y is therefore unable to control the repeater or in any way change the condition of the connection established at position X by manipulating her controlling keys. Should the operator at position Y fail to observe the busy lamp 7 and insert either or both of the plugs P, and P in the jacks of toll lines, the toll lines in question will be connected in parallel with the toll lines interconnected through the repeater at position X. However, at the same time suitable balancing artificial lines are connected in parallel to the artificial lines involved in the connection at station X so that the repeater is not unbalanced and therefore does not sing. The operator at position Y is unable, by throwing her listening key, to bridge her set across the connection and will therefore realize that the repeater is in use and will withdraw the plugs inserted in the toll line jacks.

With the apparatus restored to normal as above described, the operator at position Y may establish a connection through the repeater at Fig. 2 by employing the plugs P and R The insertion of the plug P, in the jack of the incoming line completes a circuit over the sleeve contacts of the plug through the left hand winding of relay 4 to battery. A circuit is also'completed over the sleeve contacts of the plug and over the inner right hand contact of relay 5 and over conductor 8 through the winding of relay 9 to battery. Relay 4 at its right hand contact disconnects battery from the windings of the relay 5 thereby rendering the latter inoperative and at its right hand front contact relay 4 completes a circuit from battery to the busy lamp 6 to indicate to the operator at position X that the repeater is in use. By opening its left hand contacts, relay 4 disconnects relays 9 and 12 from the sleeve conductors of plugs P and P Relay 4 at its right hand front contacts also completes a circuit from battery over conductor 63 and through the windings of relays 1., 2 and 3 in parallel to ground. These Relay 9 at its lower front contact upon being energized completes the previously traced circuit of the relay 19 which holds open the circuit of the relay 20. Atransr mission connection now exists from the incoming line over the left hand tip and ring 7 contacts of the plug P, over conductors L and L, back contacts of relay 21, conductors C, front contacts of relay 3, conductors C,, over the normal contacts of splitting key K over conductors G front 30 contacts of relay 2, conductors C, back contacts of relay 23 and over conductors L and L to the right hand tip and ring contacts of plug P The operator by throwing listening key K, may bridge her set across the transmission clrcuit above traced.

In order to complete the connection, the operator will insert the plug P in the jack of the outgoing line and throw the repeater control key K the listening key K, being restored to normal. A circuit is completed over the sleeve conductor of the plug P through the right hand winding of relay 4 and over the back left hand contact of relay 5 to battery but as relay 4 is already energized this circuit is without effect. A cir cuit is also completed over the sleeve conductor of the plug P and over the right hand back contact of relay 5, over conductor 11 and to the winding of relay 12 to battery.

Relay 12 at its lower contact now connects ground to point 13 in parallel with the ground applied to said point over the lower contact of relay 9.

A circuit for the filament control relay 29 is completed from battery through the winding of said relay over conductor 30, right hand front contact of relay 3, conductor 31, right hand make contact of key K, over conductors 32, 33 and 14to grounded point 13. A circuit is also completed for relays 44,21 and 23 from grounded point 13 over conduc tor 34, front right hand contact of relay 1, conductors 35' and 36, over the lower normal contacts of key K over the right handJlS normal contact of listening key K over conductor 37 inner left hand front contact of relay 1, conductor 38, upper front contacts of relays 9 and 12, conductors 39 and 40, left hand make contact of key K conductors 41', 42 and 43'through the winding of relay 44 over the back contact of relay 45, over conductor 46, through the windings of relays 21 and 23 to battery. The energization of relays 29, 44, 21 and 23 results in the same certain changes as already described with reference to the connection established at position X.

With the circuit in this condition, transmission from the iQQQIDiI g line passes over 20 in: a manner already described.

conductors L and L, over the front contacts-of relay 21 through input bridge 49, transformer 47 and amplifier A to output circuit 53 and outgoing transformer 52 where 1 thegenergy divides, part being transmitted over the front contacts of relay 23 and conductors L and L to the outgoing line and part being transmitted over conductors N and N to the artificial line. In a similar manner transmission incoming from the outgoing lines passes over conductors L L and the: front' contacts of relay 23 through input bridge 50 and transformer 48 and through amplifier A of the repeater to the outgoing transformer 51 Where'the energy divides, part being transmitted over the front contacts of relay 21 and conductors L and L to the incoming line and part being transmitted over conductorsv N and N to the corresponding artificial line.

Should ringing current be transmitted over the incoming line the relay 1'? will be energized to open the circuit of relay 19 which, in turn, completesthe circuit of relay Relay 20 at its right hand front contact completes the circuit of relay 45 over a path extending from grounded point 13 overconductor 34, right hand. front contact of relay 1, conductors- 35 and 36, lower normal contacts of the splitting key K right hand normal contact of listening key toconductor 37, inner left hand front contact of relay 1 conductor 38, upper front: contacts of relays 9 and 12, conductors 39 and 40, left hand make contact of key K conductors 41, 42'

and 55 over the right hand front contact. of relay 20 and through the windings of relay 45 to battery. The energization'of relay 45 produces circuit changes similar to those already described with reference to the 0011- nection set up at position X.

Relay 20 at its left hand front contact completes the circuit of relay 56 which is locked up over-a circuit extending over its upper frontcontact over conductors 5'7 and 58 over the left hand normal contact of key K over conductors 59 and 35, right hand front contact of relay 1 and over con.- ductor 34 to grounded point 13. At its lower front contact relay 56 completes a eircuit from ground over conductor 60, left hand front contact of relay 1 and through the lamp 61 to battery. The glowing ,of lamp 61" indicates to the operator that a ring has been transmitted over one of the connected lines. The operator may thenactuate her listening key which causes the deenergization of relay 56 thereby efi'acing the lamp 61. The actuation of the listening key also opens the circuit of relay 45 and causes a den'ergization of relays'21 and 23 inaddition to relay 44. The two toll lines are. now directly interconnected through the cord- 'circuit connections including conductors C, C

ing current was transmitted from the out-, I

going line, ringing responsive relay 16 would be actuated to again restore the slow release relay 19 which in turncompletes the circuit of relay 20; The energization of relay 20 does: not complete the circuit of rclay 45 as the circu it of said relayv is heldopcn at the contacts of thekeys K and K The circuit of relay 56, however, is corn-. pleted at the left hand front contact of relay 20 and relay 56 at its upper front contact establishes a locking circuit over conductors 57. 58 and 62", over the lower left hand make contact of'splitting key K over the lower right hand normal contact of said key, over conductors 3:6 and 3-5; right hand front contact of relay 1 and over conductor 34 to grounded point 13. Relay 56- com pletes the circuit of the lamp 61 thereby indicating to the operator that, a'ring has come in from the outgoing line. The operator may then throw the splitting key to the right in order to communicate over the outgoing line to the exclusion of the incoming line.- The operation momentarily opens the look ing circuit'of relay 56 which is deenergized and eff'aces the lamp 61.

As soon as the operator restores the listening and splitting keys, K and K respectively, the circuit of relays 44, 21 and 23 is again completed so that the repeater is once more rendered operative and is again connected in the transmission circuit previously described. The connection may be taken down by withdrawing plugs P and P and restoring the repeater control key K Relays 4, 9 and 12 are deenergized upon with drawing the plugs. e Thevcl'eenergization of relay 4 restores switching relays 1, 2 and? to normal and the dei-Snergization ofrelays 9 and 12 by disconnecting ground from point 13 restores relays 19 2.9., 44', 21 and 23. to normal. e

It'will be observed that-under the conditions-just describedthe connections from the repeater to the controlling keys K' f, K and- K at position Y were wholly under the control of the operator at saidposition and the corresponding connections to the keys. at position X were held open so: that the operator at the latter position was unable to control the repeater'or in any manner affect the connection established at position Y. Should the operator at position X disregard the busy lamp and attempt toconnect to a transmission line, she would, therefore be unable to listen in on the line and even though the line be connected in parallel with a line involved in the connection established at position Y, the repeater would not be unbalanced for the reason that a corresponding artificial line would be connected in the circuit at the same time.

By means of the arrangement above described, the same repeater may be used for establishing connections at two positions thereby eliminating a certain amount of apparatus with a consequent reduction in the expense involved in the installation.

It will also be observed that the general principles herein disclosed may be embodied in many other organizations widely diflerent from that illustrated without departing from the spirit of the invention as defined in the following claims.

What is claimed is:

1. In a signaling system, a repeater, a plurality of lines, a plurality of sets of switching apparatus for associating the repeater with a line, parallel transmission connections extending from said repeater to each set of switching apparatus, keys associated with each set of switching apparatus for controlling the functioning of the repeater, and means whereby when the repeater is associated with a line by one set of switching apparatus the repeater will be rendered independent of the controlling keys of another set of switching apparatus without disturbing said parallel transmission connections.

2. In a signaling system, a repeater, a plurality of switch board positions, lines terminating at said positions, parallel transmission connections extending from said repeater to each position over which said repeater may be associated with lines at that position, controlling keys at each position, connections whereby the control of the repeater can be extended to the keys at any one of the positions, and means whereby when the repeater is associated with a line at one position the connections from the repeater to the corresponding controlling keys will be established and the repeater rendered independent of other controlling keys without disturbing said parallel transmission connections.

3. In a signaling system, a repeater, a plurality of switch board positions, lines terminating at said position in jacks, cords at each position terminating in plugs adapted to cooperate with said jacks, parallel transmission connections extending from the repeater to the plugs at different positions, controlling keys at each position, connections whereby the control of the repeater may be extended to the controlling keys at any one of the positions, and means responsive to the insertion of the plugs at one position in the jack of a line at that position to establish a connection from the repeater to the controlling keys at that position and render the repeater independent of keys at another position without disturbing the parallel transmission connections to other plugs.

4. In a signaling system, a repeater, a plurality of switch board positions, lines terminating at said positions in jacks, cords at each position terminating in plugs adapted to cooperate with said jacks, parallel transmission connections extending from the repeater to the plugs at diilerent positions, controlling keys at each position, connections normally extending from the repeater to the controlling keys at one position, and means whereby when a plug at another position is inserted in the jack of a line at that position the repeater is disconnected from the keys at the first position and connected to the keys at the second position without disturbing the parallel transmission connections of other plugs.

5. In a signaling system, a repeater, a plurality of lines, a plurality of sets of switching apparatus for associating the repeater with a line, parallel transmission connections extending from said repeater to each set of switching apparatus, keys associated with each set of switching apparatus for controlling the functioning of the repeater, busy signals associated with each set of switching apparatus, and means whereby when the repeater is associated with a line by one set of switching apparatus the repeater will be rendered independent of the controlling keys of another set of switching apparatus without disturbing said parallel transmission connections, and whereby a busy signal associated with said other set of switching apparatus will be operated.

6. In a signaling system, a repeater, a plurality of switch board positions, lines terminating at said positions, parallel transmission connections extending from said repeater to each position over which said repeater may be associated with lines at that position, controlling keys at each position, connections whereby the control of the repeater can be extended to the keys at any one of the positions, busy signals at each position, and means whereby when the repeater is associated with a line at one position the connections from the repeater to the corresponding controlling keys will be established and the repeater rendered independent of other controlling keys without disturbing said parallel transmission connections, and whereby a busy signal at another position will be operated.

In testimony whereof, we have signed our names to this specification this 16th day of May, 1919.

CHARLES S. DEMAREST. SAMUEL P, SHACKLETON.

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