US1576747A - Telephone system - Google Patents

Description

March 16 1926. 1,576,747

H. L. HOFFMANN TELEPHONE SYSTEM Filed Dec. 22, 1923 2 Sheets-Sheet 1 /5 xLG March 16 1926.

' 1,576,747 H. L. HOFFMANN TELEPHONE SYSTEM Filed Dec. 22, 1925 2 Sheets-Sheet 2 fim/ Alfaffmmn M My Patented Mar. 16, 1926.

UNITED STATES arana orries- HENRY L. HOFFMANN, OF EA ST ORANGE, NEVI JERSEY, ASSIG-NOR TO.XVESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

TELEPHONE SYSTEM.

Application filed December 22. 1923. Serial No. 882,198.

To all whom it may concern Be it known that I, HnNnY L. HOFFMANN, a citizen of the United States of America residing at East Orange, in the county-0t Essex and State of New Jersey, have invented certain new and useful Improvements in Telephone Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to telephone exchange systems, and more particularly, to

improvements in the trunk circuit for establishing a connection between manual exchanges.

The invention is adapted for use in systems in which calls received at a manual switchboard at one exchange are extended by means out so called A operators link cir cuits and trunk lines terminating at another exchange and from there by means of so called B operators link circuits at this latter exchange to a desired subscribers line. In such systems a number of trunk circuits and a number of B operators link circuits are usually provided and any one of the link circuits may be used for extending the connection to the wanted subscriber by inserting one plug thereof in the jack of a chosen trunk and the other plug in the jack of a wanted subscriber's line and the B operators telephone set is manually connected to such a link circuit by means of a key. lhe trunk used is ordinarily assigned by the aid of a separate call wire circuit extending between the two exchanges which is available for this purpose to the operators at the two positions.

An object of this invention is to eliminate the use of call wire circuits to assign trunk lines by the provision of a so called straight forward trunking system embodying means whereby the A operator may connect with any one of the trunk lines leading to the exchange in which the wanted subseribers line terminates and whereby the B operator may select any available link circuit and by manually connecting it to the wanted subscribcrs line automatically extend the connection from the seized trunk line to the wanted subscriber.

Another object is to automatically connect the B operators telephone equipment with a trunk line the moment it is seized by the A operator.

Another object is to automatically disconpervisory signals between the two operators positions for the purpose of controlling the connection during the setting up operations as well as during the conversation or at the release of the connection.

Another object'is to automatically ring a wanted subscribers line when the connection is completed.

Another object is to provide means whereby it the B operator transfers a connection from one seized outgoing line to another as, for example, from a line terminating in a supervisory or monitoring board to a line terminating at a substation, said second line is automatically rung in a manner similar to that in which the first line was called.

To attain these objects in accordance with i one feature of the invention the incoming trunk lines and the B operators link circuits terminate in switching devices by means of which any link circuit taken for use may be automatically associated with the seized trunk line the moment it is manually connected to the wanted subscribers line.

Anotherfeature is the provision of an arrangement including a second switching device which is actuated the moment a trunk circuit is seized by the A operator to connect the B operators telephone equipment with said trunkline and a circuit arrangement for automatically disconnecting this equipment from the trunk line the moment the manual connection to the wanted subscriber is completed.

Another feature resides in the provision of signaling means whereby the B operator is notified when the trunk circuit has been seized for the extension of a call and when her telephone equipment is connected to or disconnected from the seized trunk line.

Another feature is the provision of means whereby the B. operator may test the wanted subscribers line for a busy condition without causing the selected link circuit to connect with the seized trunk line and whereby it the subscribers line is busy, she may send a distinctive signal over the seized trunk line to the A operator to call her attention to this condition.

Another feature is the provision of a signaling means whereby if the B operator disconnects accidentally or otherwise, the link circuit connected to the wanted subscribers line before the A operator is disconnected from the trunk line the B operator is notified in a distinctive manner of this fact.

Another feature is the provision of a signaling means whereby the B operator receives a distinctive signal if the A operator disconnects her link circuit from the seized trunk line.

Another featureis the provision of means for ringing the wanted subscribers l ne automatically when the link circuit is con nected to such line and ringing a second subscribers line when the link circuit is transferred thereto while the A operator'is still connected to the seized trunk line and without disconnecting the/link circuit from said trunk line.

Another feature of the invention is .the provision of means whereby the A operator receives a distinctive signal if she has connected with a trunk terminating at an unattended B operators position.

One embodiment of the invention is illustrated in the accompanying drawings in which Fig. 1 shown an A operators link circuit at one manual exchange; a. manual subscribers line terminating thereat and the terminating end of a trunk line leading to another exchange.

Fig. 2 shows the incoming end of said trunk line in anothermanual exchange and a B operators link circuit and telephone equipment embodying the features of this invention and also a wanted subscribers line terminating thereat.

Referring now to the drawings a calling subscribers line 1 terminates in jack 2 in a manual switchboard and an A operators link circuit may be employed to connect line 1 with trunk line C teuninating in a jack 16 and extending from there to another manual exchange where it may be connected through the medium of switch to a B operators link circuit D, which link circuit,

in turn, may be connected by means of plug 65 to a jack 66 of a wanted subscribers line 100. The trunk line C, which may be one out of a group of similar trunk lines extending between the two exchanges, may be connected in common with such trunks to the bank terminals of switch 80 as shown, and it is understood that these trunks may also be multipled to the the bank terminals of a number of other similar switches and the movable terminals of each switch connected to a separate link circuit such as D. Such a group of link circuits may then be located in a manual switchboard available to a B operator as is the practice where ordinary B operators link circuits are used. The B operators telephone equipment shown belowthe dotted line in Fig. 2 is common to thesetrunk lines andlink circuits and may be associated with any one of the trunk lines by means of a common relay arrangement and a switch 60. As the construction of the switches 80 and 60 forms no part of this invention no de tail description will be given except to say that'they may be of the well known finder type, the brushes or movable terminals of which may be moved in a step-by-stcp fashion. The brushes of switch 80 may be moved by the stepping magnet 69 and the brushes of the switch 60 may be moved by means of the stepping magnet 44 and as these switches have no normal position the brushes will remain on the terminals to which they were last advanced.

The invention is best understood by describing the setting up ofa connection between a calling subscribers line 1 and a called subscribers line by means of the arrangement shown in the drawings and such a connection will now be described.

Assuming that the subscriber on line 1 has initiated a call in the usualmanner and that A operator has answered it by the insertion of plug 3 in jack 2 and connected her telephone set to the link circuit A by the operation of listening key 10 and received from the calling subscriber the num ber of the wanted subscriber, she proceeds by inserting the calling plug 15 in a jack such as 16 of any link circuit such as G leading to the exchange in which the wanted subscribers line 100 terminates. It will be observed that it is not necessary for the A operator to have any particular trunk line leading to the desired exchange assigned her, but she may, on the contrary, connect with any of the trunks at the moment most conveniently at hand. hen, therefore, a connection to any one of the trunks is completed as in this case to trunk line C, circuits are established to connect the B operators telephone equipment to this selected trunk as follows: The first circuit is completed'from battery at the A operators link circuit, the lower right hand winding of repeating coil 17, supervisory relay 18, ring contacts of plug 15 and jack 16, lower left hand winding of repeating coil 30, left hand winding of relay 10, upper left hand winding of repeating coil 30, tip contacts of jack 16 and plug 15, upper right hand winding of repeating coil 17 to ground. This circuit energizes relay 18 to cause the shunting and extinguishment of the supervisory lamp 19 in a well known manner and at the dis tant exchange energizes relay 40. The operation of relay 40 establishes a circuit for relays 4.1 and 42 from battery, armature and contact of relay 10, outer left hand armature and back contact of relay 91, make before break contacts of relay "i'l, winding of relay 41, resistance 77, winding of relay 4-2 to ground.

The operation of relay 42 closes a circuitfor lamp 43 over an obvious circuit to notify the B operator that a connection is desired, and this relay also closes a circuit for the steppin magnet 44 from battery, winding of stepping magnet 44, armature and back contact of this magnet, right hand armature and front contact of relay 42, left hand armature and back contact of relay 45 to ground. The stepping magnet 42 now through its self-interrupting contacts is caused to vibrate and in the well known manner in switches of this type advances thereby the brushes 50 and 51 in a step-bystep fashion to hunt for the selected trunk line C and when brush 50 linds the terminal 52 in its contact bank which represents trunk C a circuit is completed from battery at 40 as previously traced to the point 53, and from there to terminal '52, brush 50, winding of relay 45 to ground. This circuit causes the operation of relay 45 and the deenergization of marginal relay as this path to ground from the battery of relay 40 is one of less resistance than that through the resistance 77 and winding of relay 42. The release of relay causes lamp 43 to be extinguished and the operation of relay 45 causes the lamp 46 to be lighted over an obvious circuit, the extinguishing of lamp 43 and lighting of lamp 46 indicating to the B operator that the trunk C has been found, and that her telephone set will presently be connected thereto.

The release of relay 42 and the operation of relay 45 open the circuit for the stepping magnet 44; the relay 42 at its right-hand armature and front contact and relay 45 at its left-hand armature and back contact, causing the magnet 44 to become deenergized and the brushes 50 and 51 thereby permitted to come to rest on the contacts corresponding to the trunk C. The purpose of brush 51 and the corresponding terminals will be described hereinafter. The operation of relay 41 extends at its inner lefthand armature and front contact and at its right-hand armature and front contact a circuit from trunk C to the inner lower armature and upper armature of relay 47, which relay is momentarilyenergized by a circuit closed by the energiaation of relay 47 as follows: battery, winding of relay 47, armature and back contact of relay 49, lefthand armature and front contactof relay 45 to ground.

The cnergis'iation of relay 47 extends the leads previously mentioned from the trunk (l to a tone producing device which thereby connected to the A operators telephone set to notify her that the B operators device is about to be connected. This tone circuit may be traced as follows: battery, lower right-hand winding of repeating coil 80, winding of relay 84, right-hand armature and back contact of relay 91, inner left-hand armature and front contact of relay 41, inner lower armature and front contact of relay 4?, through the secondary of the tone producing device AT to upper arn'lature and front contact of relay 47, right-hand armature and front contact of relay 41, upper right-hand winding of repeating coil 30 to ground, and the repeated circuit through the left-hand windings of the repeating coil 30, through the trunk C, jack 16, plug 15, listening key 10 to the operators telephone set.

As stated this circuit is only maintained for a short interval as the operation of relay 47 extends an energizing circuit for relay 48 as follows: battery, upper winding of relay 48, outer lower armature and front contact of relay 4'7, armature and back contact of relay 49, left-hand armature and front contact of relay 45 to ground. Relay 48 is thereby operated and locks up to ground at relay 45 and at the same time causes the energization of relay 49 over a circuit from battery, lower winding of relay 48, outer lower armature and front contact of this relay, vinding of relay 49, left-hand armature and front contact of relay 45 to ground, and the operation of relay 49 at its armature and back contact causes the release of relay 47. The release of relay 4'? and the operation of relay 48 now, therefore, removes the tone producing device AT from the circuit to the A operators telephone set and extends this circuit to the B operators telephone set OT as follows: The relay 4-7 at its inner lower armature and back contact and upper armature and back contact and the relay 48 at its inner lower armature and front contact and upper armature and front contact. The A. operator on noticing the tone may therefore immediately transmitto the B operator the number of the wanted subscriber and then release her listening key 10 and pays no further attention to the connection until it has been extended or until it is ready for release, of which she will be notified either by distinct signals that the connection has been completed or that the wanted subscribers line is busy or that the conversation between the subscribers is at an end. 7

As soon as the B operator receives the number of the wanted subscriber she procccds to complete the connection as follows: She may select out of a number of link circuits, such as l) any most conveniently at hand and test the wanted subscribers line in the usual manner by touching the sleeve of the jack with the tip of the selected plug and thus if the wanted subscriber is busy cause the operation of the usual busy tone device SET associated with-her position. If the B operator receives such a busy tone she will immediately notify the A operator of this-fact by depressing a key such as 61 or 62 whichever is most C0l1- vcniently at hand, one of these keys being located on the righthand side and the other on the left hand side of the position. The depression of one of these keys, for example (32, causes busy signal indications to be transmitted to the A operator by the following circuit from battery, armature and front contact of relay 40, winding of relay 91, bank terminal 92 and brush 51 of switch 60, l-rcy 62 to ground. This circuit causes the operation of relay 91 which now locks up through its own inner left-hand armature and front contact to. ground from the'battery at relay 4-0. The operation of relay 91 extends the busy signal circuit to the A operators position as follows: from battery, lower right-hand winding of repeating coil 30, windi k of relay 8%, right-hand armature and front contact of relay 91, key 90, secondary winding of the busy tone produc ing device BBT interrupter 93 to ground. This circuit through the interrupter 93 causes the alternate operation and release of relay 8t which thereby opens and closes at its armature and front contact a shunt circuit through the right-hand winding of re layer). The inclusion of this shunt winding across the conductors of trunk line C causes the alternate release and operation of the supervisory relay 18 and the consequent flashing of lamp 19 in the well known manner. It will also be noted that if {the operator has not yet disconnected her telephone from the link circuit A by the release of listening key 10, she will at this time in addition to the flashing signal also receive a busy tone signal in her receiver as the busy tone producing device BBT has as stated its secondary winding included in the above traced circuit as shown, this arrangement being provided as an additional means for the speeding up of the service. These signals continue to operate until the A operator removes her plug 15 from the jack 16.

It should also be noted that the B opcrators telephone is immediately removed from the trunk line at the operation of key 62 as the relay 91 at its outer left-hand armature and back contact opens the circuit for relays 4E5 and 41. The release of relay 45 causes the lamp 16 to be extinguished and relays 1-9 and 4:8 to be released, and the release of relays Q8 and 49 cause the B operators telephone equipment to be disconnected from the trunk line C.

On the other hand, in case the wanted subscriber is not busy the B operator will complete the connection by inserting plug 65 fully into the jack 66 and thus cause relay 67 to be energized over an obvious circuit. The operation of relay 67 immediately causes the lighting of lamp 68 over a circuit from battery, armature and back contact of relay 94, lamp 68, second lower armature and front contact of relay 67, enter righthand armature and back contact of relay to ground to indicate to the B operator that the line is functioning. The operation of this relay 67 also causes the finder switch associated with this link circuit D to begin its hunting operations for the selected trunk line C and to this end a circuit is completed for the step-by-step magnet 69 as follows: battery, third lower armature and front contact of relay 67, winding of magnet ('39,.the armature and back contact of this magnet, inner right-hand armature and back contact of relay 70 and make before break contacts of relay 73 to ground. The stepping magnet 69 ope ates in a step-bystep manner by interrupting its own contacts and thus advances in the well known manner the movable brushes 81, 82 and 83 of the switch 80 until the brushes 81 and 82 come in contact with the terminals of trunk C and brush 88 comes in contact with terminal 8%, which latter connection closes a circuit from battery, at the outer left-hand armature and front contact of relay 41, which it will be remembered was energized at the time the trunk circuit C was seized, through the winding of relay 71, the above mentioned contact 84: and brush 83, left hand armature and back contact of relay 73,.left-hand winding of relay 70 and inner lower armature and front contact of relay 67 to ground. This circuit causes the operation of relays 71 and 70. Relay 71, in operating, substitutes in this circuit for the battery at the outer left-hand armature and front contact of relay 11 the battery at relay 4:0 and by means of its contacts, opens the holding circuit for relays 11 and 15 and thus causes the immediate disconnection of the B operators telephone equipment from the trunk line C as previously explained. The operation of relay 70, on the other hand, opens at its inner right-hand armature and back contact the circuit for the stepping magnet 69, causing the switch 80 to stop with the brushes 81 and 82 in connection with the trunk line C and the brush 83 remaining in Contact with the terminal 84. This relay 70 also causes the operation of relay 73 over a circuit from battery, third lower armature and front contact of relay 67 right-hand winding of relay 73 inner right-hand armature and frontcontact of relay 70, right-hand make-beforebreak con tacts of relay 73 to ground, causing relay 73 to lock up over an obvious circuit via its inner right hand armature and a makebefore-break contact thereof to ground, and also over its lefthand armature and front contact and the right-hand winding of relay 70 to ground. Relay 70 being thereby locked up in series with relay 7 3 to battery of relay an independent of the ground at the inner lower armature and front contact of relay 67. The purpose of this relay ope 'ation will become apparent as the description proceeds.

It is further noticed that relay 70 opens at its outer right-hand armature and back contact the circuit for the lamp 68 which is thereby GXQlDgUiSllQCl to indicate to the B operator that the link circuit D is' about to be connected to the trunk line C and that automatic ringing of the wanted subscriber has been applied as a circuit was completed at the outer right-hand armature and front contact of relay 70 at its energization for relay 72 as follows: battery, armature and back contact of ringing relay 7 4i, outer-lower armature and back contact of relay 75, winding of relay 72, fourth lower armature and front contact of relay 67 outer righthand armature and front contact of relay 70 to ground. This circuit causes the operation of relay 7 2 and ringing current is there fore applied from the source 76 through the winding of ringing relay 74, inner lower armature and back contact of relay 7 5, lower arniature and front contact of rglay 7 2, ring contacts of plug 65 and jack 66, through the wanted subscribers bell, back through the tip contacts of jack 66 and plug 65, upper armature and front contact of relay 67, upper armature and front contact of relay 72, upper armature and back contact of relay 7 5 to ground. When the called subscriber answers in the usual manner by lifting his receiver from the hook, relay 74 operates and disconnects the battery at its armature and back contact from the circuit for relay 7 2, which now receives a substitute battery through the winding of relay 7 5 formerly shunted by'the first mentioned battery, causing relay 7 5 to operate to open the ringing circuit at its upper armature and back contact and inner lower armature and back contact and substituting therefor at its upper armature and front contact and inner lower armature and front contact the leads connecting the brushes 81 and 82 with the conductors of the trunk line C. The calling subscriber at station 1 is now, therefore, connected through to the called subs scriber and conversation may take place. The A operator is notified of this fact by the opcratipn of relay 841. the n'loment relay 75 is operated, as relay 8% in operating causes the right-hand winding of relay l 'to be shunted across the conductors of the trunk C to operate relay l8 and extinguish lamp 19.

'lll'ierelease of the connection may be initiated by either subscriber replacing his receiver on the hook If the calling subscriber hangs up lamp will be lighted or if the called subscriber hangs up lamp 19 will be lighted by the release of relay 84 in the well known manner. In either case it is the duty of the A operator to release the connection by removing the plugs 3 and from jacks 2 and 16, respectively, and when the trunk line C is thus released relay 40 is released, causing the release of relays 71 and 7 O which as previously explained were held operated by the battery at the contacts of relay 40. Relay 70, in releasing, causes the release of relays 72 and 75, thus opening the connection of the link circuit to the trunk line C. The release of relay 7 also causes lamp 68 to be lighted to maintain a steady glow by closing a circuit at the outer right-hand armature and back contact to ground for this lamp from battery at the armature and back contact of relay 94- if the wanted subscriber has in the meantime hung up his receiver, thus notifying the B operator that the A operator has released the connection and the B operator will now remove. her plug from jack 66, thus releasing relay 67, extinguishing the lamp 68 and releasing relay 73.

On the other hand if the called subscriber has not replaced his receiver, the B operator will be apprised to remove plug 65 from jack 66 as follows: Relay 94 will be operated when relay 72 is released by a. cir cuit from battery through its right-hand winding lower armature and back contact of relay 72 through the called subscribers loop back to the upper armature and back contact of relay 72 left hand winding of relay 94; to ground, and thus connect the interrupter 96 to the circuit for lamp 68 which will then indicate this fact to the B operator by a flashing signal. Should the subscriber at this moment and prior to the removal of plug 65 from jack 66 by the B operator, notice that he had been disconnected, desire to reestablish the connection he will move his receiver up and down and thus alternately cause the lamp 68 to flash or burn with a steady glow and thus indicate to the B operator that he desires the connection to be reestablished.

In case of accidental removal of plug 65 from jack 66 before either of the subscribers desires a connection to be, released, the signal 68 is automatically flashed to indicate this fact to the B operator as-follows: Relay 67 is released whereas relay 78 is still held operated by the holding circuit from battery at relay 40 and a circuit for the lamp 68' is, therefore, completed from bill)" tery armature and back contact of relay 94:, lamp 68, second lower armature and back contact of relay 67, outer right-hand armature and front contact of relay 73, interrupter 76 to ground. When the B operator receives this flashing signal she in1- mediately again inserts the plug 65 in jack 66 and thus restores the connectioi'i her ma l The releas'e'o'f relay 67 in this case will also cause'the temporary release of relays 72 and 75 asthe circuit for these relays are controlled by the fourth lower armature and "front contact of relay 67 and ifthe subscriber 100had'inthe meantime hun n) his receiver he would a- 'ain be c l 7 t:

called by the connection of the ringing:

In otherwords, the arrangement is such that the plug i65 can be transferred from 0116"]21Ck to another and the ringing operations repe'atedeach timeto' call the *party'uponthe line connected withat the moment.

An arrangement is also "provided whereby in case the B operators position'has to be left unattended, a signal is transmittedto the A" operators position when she has seized the trunk leading tothis operators position, and to this end key may be depressed and locked to'connect the busy tonedevice OBT to thesei'zed trunk. hen, therefore, a trunk C is seized, switch 60 operates, as herein'b'efo're' described, to find the 'B operators equipment, but instead of functioning to connect her telephone set, the relay '91 operatesoveraclrcuit froin battery, armature and front contact of relay 40, winding ofrelay 91, stationary terminal 92, movable terminal51, lower operatedcontacts of key 90'to ground, and relay'91 is thereby locked up from battery at relay 40 through its innerleft hand armature and front contact to ground. The-operation of relay 91 breaks at theouter left hand arma ture and back contact the energizing circuit for relays 42 and 45, preventing the B operators telephone set from being co nectedto the seized trunk, and by the operation of its'right hand armatureand front contact'closes a circuit for the busy tone device OBT asfollows: from battery, lower right hand winding of repeating coil 30, wi'ndingcof relay 84, right hand armature andifr-ont contact of relay 9 1,,u-pper operated-contacts of key 90, secondary" winding of the busy tone. device OBT to ground. The busy tone is thus transmitted to the repeating coil 30 and repeated to the A operator's telephone set over a circuit, as previously described, to indicate to the A operator that the B operators position is unattended. When the A operator disconnects her plug 15 from the seized trunk jack 16, relays 40 and 91' are'releas-ed;

What is claimed is:

1. A telephone'systeni comprising. trunk lines, an'operatorstelephone set, a first subscribers line, means responsive to the connection of said first subscribers line to any one of said trunks to connect'th-e opcratoifs telephone set thereto, a second subscribers line, a link circuit for connecting to said second subscribers line, and means operative upon the connection of said link circuit to said second subscribers line to connect said link circuit tothe said trunk circuit."

2. A telephone system comprising trunk lines, an'operators telephone set, a calling line, means for connecting any one of said trunks to said calling line, an electromagnetic means operative when a trunk is seized to connect the operators telephone setthereto, other subscribers lines, a'link circuit'for connectingwith any one ofsaid other subv scribers lines, and a secondelectromagnetic means operative responsive to the connection of said link circuit to one of said other sul scriber's lines for connecting the link circuit to the trunk line.

3. A telephonesyst'em" comprising trunk lines, anopera-tors telephoneset, means for seizing any one of said trunks, a finder switch responsive thereto for connecting the operato'rs telephone set to the seized'trunk, subscribers lines, a'link'cir'cuit for connecting 'with'any one of said subscribers lines, and a secondfinde'rswitch responsive to the seizin'gj'of a subscribers" line by the link circuit and the seizure of the trunk line for connectingthe link circuit-to the trunk line.

4:. A 'telephone'system comprising trunk lines, an operators telephone set, means for seizing any one of saidtrunks, automatically operated means responsive thereto for connecting the operators telephone set to the seizedt'runk, subscribers lines, a link circuit forconnecting with any one of said subscribers lines, and a second automatically operate'dmeans responsive to the seizure of the subscribers line bythelink circuit and the seizure ofthetrunk circuit for associating thelinkcircuit with the seized trunk line;

5. A telephone system comprising trunk lines, an operators telephone set, a first sub scribers-line, means for connecting any one of said trunks to said first subscribers line, means for automatically connecting the op erators telephone set to a trunk line when said'trunk'line is so seized, subscribers lines, a link circuit for connecting with any one of said subscribers lines, means for automatically connecting the link circuit to said seized trunk line when the link circuit has seized-a subscribers line;

6. A' telephone system comprising. trunk lines terminating at one end in jacks, a-link circuit having a plug adapted for connection aware? with the jack of any one of said trunk lines, an automatic switch in which the other end of said trunk lines terminate, a second link circuit tern'iinatmg at one end in said switch and at the other end in a plug, subscribers lines having -jacks for the connection with the plug out the link circuit, an operators telephone equipment, means including a switch for connecting automatically the operators telephone equipment with a trunk line having been seized by said first mentioned link circuit, and means associated with said second link circuit for operating said first mentioned switch to connect this link circuit with said seized trunk line when said link circuit has seized a subscribers line.

7. A telephone system comprising trunk lines, an operators telephone set, a first subscribers line, means for connecting any one of said trunks with said first subscribers line, means operative when a trunk is so seized to connect the operators telephone set thereto, other subscribers lines, a link circuit for connecting with any one of said other subscribers lines, means operative responsive to the connection of said link circuit to one of said other subscribers lines to connect the link circuit with said trunk line, and means operative when said other subscribers line is seized for disconnecting the operators telephone set from the seized trunk line.

8. A telephone system comprising trunk lines, an operators telephone set, a first subscribers line, means for connecting any one of said trunks to said first subscribers line, means operative when a trunk is so seized to connect the operators telephone set thereto, other subscribers lines, a link circuit for connecting with any one of said other subscribers lines, means operative responsive to the connection of said link circuit to one of said other subscribers lines to connect the link circuit with the trunk line, and means operated when the link circuit is connected to the seized trunk line to disconnect the operators telephone set therefrom.

9. A telephone system comprising trunk lines, an operatoi."s telephone set, a first subscribers line, means for connecting any one o't said trunks with said first subscribers line, means operative when a trunk is so seized to connect the operators telephone set thereto, means to indicate the seizure of a trunk, other subscribers lines, a link circuit for connecting with any one o't said other subscribers lines, and means operative responsive to the connection of said link circuit to one of said other subscribers lines to connect the link circuit with the trunk line.

i0. A telephone system comprising trunk lines, an operators telephone set, a first sub scribers line, means for connecting); any one of said trunks with said first subscribers line, means operative when a trunk is so seized to connect the operatofis telephone set thereto, a signaling means operated in response to the connection oi an operators telephone to the seized trunk, other subscribers lines, a link circuit connected with any one of said other subscribers lines, and means operative responsive to the connection of said link circuit with one of said other subscribers lines to connect the link circuit with the trunk line.

11. A telephone system comprising trunk lines, an operators position at one end of said trunks, a first subscribers line terminating at said position, an operators position at the other end of said trunks, means at the first mentioned operators position for connecting any one of said trunks, means operative when a trunk is seized to connect the second mentioned operators telephone equipment thereto, means for indicating to the first mentioned operator when the second mentioned operators equipment is associated with the seized trunk, other subscribers lines, a link circuit at the second operators position for connecting with any one of said other subscribers lines, and means operated responsive to the connection of said link circuit to one of said other subscribers"lines to connect the link circuit with said trunk line.

12. A telephone system comprising trunk lines, an operators position at one end of said trunks, an operators position at the other end of said trunks, means at the first mentioned operators position for seizing any one of said trunks, means operative when a trunk is seized for connecting the second mentioned operators telephone equipmentt'hereto, a means operated in response to the connection of the second mentioned operators equipment to the seized trunk to transmit a momentary signal to the first mentioned operators position over said seized trunk, subscribers lines, a link circuit for connecting with any one of said subscribers lines, and means operative when a trunk line and a snhscribeids line are seized to connect the link circuit with the trunk line.

13. A telephone system comprising trunk lines, an operatofls position at one end o't said trunks, an operatofls position at the other end of said trunks, means at the first mentioned operations position or seizing any one of said trunks with said first sul scribers line, means operative upon the seizure of said trunk to connect the second mentioned o1j eratoi"s telephone set thereto, a signaling means associated momentarily with a trunk when it is seized to transmit to the first mentioned operators position an audible signal to indicate that the second mentioned oierators telephone set is about to be connected therewith, subscribers lines,

a link circuit for connecting with any one of said subscribers lines, and means operative when the trunk line and a subscribers line are seized to connect the link circuit with the trunk line.

let. A telephone system comprising trunk lines, an operators position at one end of said trunks, an operators position at the other end of said trunks, means at the first mentioned operators position for seizing any one of said trunks, means operative when a trunk is seized to connect the second mentioned operators equipment thereto, a signaling means associated with the trunkin response to its seizure to transmit to the first mentioned operators position an audible signal and disassociated from the trunk when the second n'icntioned operators equip ment is connected to said seized trunk, sub scribcrs lines, a link circuit for connecting with any one of said subscribers lines, and means operative when the trunk line and a subscribers line are seized to connect the link circuitwith the trunk line.

15. A telephone system comprising trunk lines, an operators telephone set, means for seizing any one or said trunks, means operative when a trunk is seized to connect the operators telephone set, thereto, subscribers lines, a link circuit for connecting with any one of said subscribers lines, means operative responsive to the seizure of said trunk line andsaid subscribers line to connect the link circuit with the trunk line, and means associated with the link circuit operative when the subscribers line is seized to indicate to the operator that the subscribers line is not otherwise engaged.

16. A telephone system comprising trunk lines, an operators telephone set, means for seizing any one of said trunks, means operative when a trunk is seized to connect the operators telephone set thereto, subscribers lines, a link circuit for connecting with any one of said subscribers lines, means opera tive' when the trunk line and a subscribers line are seized to connect the link circuit with the trunk line, and a visual signal in said link circuit operated when a subscribers line is seized to indicate that the subscribers line is not otherwise engaged.

17. A telephone system, comprising trunk lines, an operators telephone set, means for seizing any one of said. trunks, means operative when a trunk is seized to connect the operators telephone set thereto, subscribers lines, a link circuit for connecting with any one of said subscribers lines, means open ative when the trunk line and a subscribers line are seized to connect the link circuit with the trunk line, and a visual signal in said link circuit operated when a subscribers line is seized and before the trunk line is connected to the link circuit.

18-. A. telephone system comprising trunk lines, an operators telephone set, means for seizing any one of said trunks, means operative when a trunk is seized to connect the operators telephone set thereto, subscribers lines, a link circuit for connecting with any one of said subscribers lines, means operative when the trunk line and a subscribers line are seized to connect the link circuit with the trunk line, means for disconnecting the link circuit from a trunk line when said trunk line is released, and signaling means operative when a link circuit is released to indicate to the operator that such a release has taken place.

19. A telephone system comprising trunk lines, an operators telephone set, means for seizing any one of said trunks, means operative when a trunk is seized to connect the operators telephone set thereto, subscribers lines, a link circuit for connecting with an y one of said subscribers lines, means operative when the trunk line and a subscribers line are seized to connect the link circuit with the trunk line, means for disconnecting the link circuit from a trunk line when said trunk line is released, anda signal intermittently operated when the link circuit is released.

20. A telephone system comprising trunk lines, an operators telephone set, means for seizing any one of said trunks, means operative when a trunkis seized to connect the operators telephone set thereto, subscribers lines, a link circuit for connecting with any one of said subscribers lines, means operative when the trunk line and a subscribers line are seized to connect the link circuit with the trunk line, and an indicating means operative when the link circuit is disconnected from the subscribers line but still connected to the seized trunk line.

21. A telephone system comprising trunk lines, an operators telephone set, means for seizing any one of said trunks, means operative when a trunk is seized to connect the operations telephone set thereto, subscribers lines, a link circuit for connecting with any one of said subscribers lines, means operative when the trunk line and a subscribers line are seized to connect the link circuit with the trunk line, and an intermittently operated signal actuated when the link circuit is disconnected from the subscriliiers line but still connected to the seized trunk line.

22, as telephone system comprising trunk lines, an operators telephone set, means for seizing any one of said trunks, means operative when a trunk is seized to connect the operators telephone set thereto, subscribers lines, a link circuit for connecting with any one of said subscribers lines, means operative when the trunk line and a subscribers line are seized to connect the link circuit with the trunk line, and an intermittently operated. visual. signal actuated when the link circuit is disconnected from the subscribers line but still connected to the seized trunk line.

23. A telephone system comprising trunk lines, an operators telephone set, means for seizing any one of said trunks, means op erative when a trunk is seized to connect the operators telephone set thereto, subscribers lines, a link circuit for connecting with any one of said subscribers lines, means operative when the trunk line and a subscribers line are seized to connect the link circuit with the trunk line, means for indieating to the operator when a subscribers line is busy, and means under control of the operator for transmitting a signal over the seized trunk line to indicate at the opposite end thereof that a subscribers line is busy.

24. A telephone system comprising trunk lines, an operators position at one end of the trunk line, an operators position at the other end of said trunk line, means at the first operators position for seizing any one of said trunk lines, means operative when a trunk line is seized to connect the second operators equipment thereto, subscribers lines, a link circuit for connecting with any one of said subscribers lines, means operative when the trunk line and a subscribers line are seized to connect the link circuit to the trunk line, means for testing a subscribers line as to its busy condition without causing the connection of the link circuit with the seized trunk line, and signaling means under the control of the second operator for notifying the first operator that a subscribers line is busy.

25. A telephone system comprising trunk lines, an operators position at one end oi. said trunk line, an operators position at the other end of said trunk line, means at the first operators position for seizing any one of said trunk lines, means operative when a trunk line is seized to connect the second operators equipment thereto, subscribers lines, a link circuit for connecting with any one of said subscribers lines, means operative when the trunk line and a subscribers line are seized to connect'the link circuit with the trunk line, means for testing a subscribers line as to 1ts busy condition without causing the connection of the link circuit with the seized trunk line, a signaling means comprising a device for transmitting a tone, a device for simultaneously transmitting an interrupted signal and a key under the control of the second operator, to notify the first operator that a subscribers line is busy.

26. A telephone system comprising trunk lines, an operators telephone set, means for seizing any one of said trunks, means operative when a trunk is seized-to connect the operators telephone setthereto, subscribers lines, alink circuit for connecting with any one of said subscribers lines, means 'erator for operative when the trunk line and a subscribers line are seized to 7 connect the link circuit with the trunk line, means for indicating to the operator when a subscribers line is busy, and means under the control of the operator for transmitting a signal over the seized trunk line to indicate at the opposite end of the trunk line that a subscribers line is busy and for disconnectmg the operators telephone set from the seized trunk. Y

27. A telephone system comprising trunk lmes, an operators position at one end of the trunk lines, an operators position at the other end of said trunk lines, means at the first operators position for seizing any one or said trunk lines, means operative when a trunk line is seized to connect the second operators equipment thereto, subscribers lines, a link circuit for connecting with any one of said subscribers lines, means operative when a trunk line and a subscribers line are'seized to connect the link circuit with the trunk line, means for testing a subscribers line as to its busy condition without causing the connection of the link circuit with the seized trunk line, signaling means under control of the second operator for notifying the first operator that a subscribers line isbusy, and means under control of the second opdisconnecting her telephone equipment from the seized trunk line simul taneously with the operation of the said signaling means.

28. A telephone system comprising trunk lines, an operators position at one end of said trunk line, an operators position at the other end of said trunk lines, means at the first operators position' for seizing any one of said trunk lines, means operative when a trunk line is seized to connect the second operators equipment thereto, subscribers lines, a link circuit for connecting with any one of said subscribers lines, means operative when the trunk line and a subscribers line are seized to connect the link circuit with a trunk line, and means at the second operators position to prevent the connection of her equipment to the seized trunk line and to transmit a signal to the first operators position over said trunk line to indicate that said second operators position is unattended.

29. A telephone system comprising trunk lines, an operators position at one end of said trunk lines, an operators position at the other end of said trunk lines, means at the first operators position for seizing any one of said trunk lines, means operative when a trunk line is seized to connect the second operators equipment thereto, subscribers lines, a link circuit for connecting with any one of said subscribers lines, means operative when a trunk line and a sub scribers line are seized to connect the link circuit with the trunk line, means including a tone transmitting device an automatic switching means and a key for connecting the device to the seized trunk and for transmitting a tone to the first operators position to indicate that a second operators position is unattended and a means operated by said last mentioned means to prevent the second operators equipment from being connected with the seized trunk.

30. A telephone system comprising trunk lines, an operators telephone set, means for seizing any one of said trunks, means operative when a trunk is seized to connect the operators telephone set thereto, subscribers lines, a link circuit for connecting with any one of said subscribers lines, means operative responsive to the connection of said link circuitto one of said subscribers lines to connect the link circuit with said trunk circuit, and means responsive thereto for antomatically ringing the seized subscribers line.

31. A telephone system comprising trunk lines, an operators telephone set, means for seizing any one of said trunks, means operative when a trunk is seized to connect the operators telephone set thereto, subscribers lines, a link circuit for connecting with any one of said subscribers lines, means operative responsive to the connection of said link circuit to one of said subscribers circuits to connect the link circuit with said trunk circuit, and means responsive thereto for automatically ringing over said seized subscribers line, and for auton'iatically reringing over a second subscribers line if the link circuit is transferred thereto from the first subscriber-7s line and not disconnected from the seized trunk.

32. A telephone system comprising trunk lines, an operator's telephone set, means for seizing any one of said trunks, means operative when a trunk is seized to connect the operators set thereto, subscribers lines, a link circuit for connecting with any one of said subscribers lines, means operative when the trunk line and a subscribers line are seized to connect the link circuit with the trunk line, means for disconnecting the link circuit from the trunk line when it is no longer seized, and signaling means operative to give a distinctive signal indication when the link circuit is no longer connected to the trunk line. and another distinctive signal when the subscriber on the connected subs'cribers line hangs up his receiver.

In witness whereof, I hereunto subscribe my name this 17th day of December A. 1)., 1923.

HENRY L. HOFFMANN.

DISCLAIMER 1,576,747.Henry L. Hofimarm, East Orange, N. J. TELEPHONE SYSTEM. Patent dated March 16, 1926. Disclaimer filed October 16, 1929, by the assignee, Western Electric Company, Incorporated.

Hereby enters this disclaimer to the said claims of said Letters Patent which are in the following words to wit:

1. A telephone system comprising trunk lines, an operators telephone set, a first subscribers-line, means responsive to the connection of said first subscribers line to any one of said trunks to connect the operators telephone set thereto, a second subscribers line, a link circuit for connecting to said second subscribers line, and means operative upon the connection of said link circuit to said second subscribers line to connect said link circuit to the said trunk circuit.

2. A telephone system comprising trunk lines, an operators telephone set, a

calling line, means for connecting any one of said trunks to said calling line, an electromagnetic means operative when a trunk is seized to connect the operators telephone set thereto, other subscribers lines, a link circuit for connecting with any one of said other subscribers lines, and a second electromagnetic means operative responsive to the connection of said link circuit to one of said other subscribers lines for connecting the link circuit to the trunk line.

4. A telephone system comprising trunk lines, an operators telephone set, means for seizing any one of said trunks, automatically operated means responsive thereto for connecting the operators telephone set to the seized trunk, subscribers lines, a link circuit for connecting with any one of said subscribers lines, and a second automatically operated means responsive to the seizure of the subscribers line by the link circuit and the seizure of the trunk circuit for associating the link circuit with the seized trunk line.

5. A telephone system comprising trunk lines, an operators telephone set, a first subscribers line, means for connecting any one of said trunks to said first subscribers line, means for automatically connecting the operators telephone set to a trunk line when said trunk line is so seized, subscribers lines, a link circuit for connecting with any one of said subscribers lines, means for automatically connecting the link circuit to said seized trunk line when the link circuit has seized a subscribers inc.

7. A telephone system comprising trunk lines, an operators telephone set, a first subscribers line, means for connecting any one of said trunks with said first subscribers line, means operative when a trunk is so seized to connect the operators telephone set thereto, other subscribers lines, a link circuit for connecting with any one of said other subscribers lines, means operative responsive to the connection of said link circuit to one of said other subscribers lines to connect the link circuit with said trunk line, and means operative When said other subscribers line is seized for disconnecting the operators telephone set from the seized trunk line.

8. A telephone system comprising trunk lines, an operators telephone set, a first subscribers line, means for connecting any one of said trunks to said first subscribers line, means operative when a trunk is so seized to connect the operators telephone set thereto, other subscribers lines, a link circuit for connecting with any one of said other subscribers lines, means operative responsive to the connection of said link circuit to one of said other subscribers lines to connect the link circuit with the trunk line, and means operated when the link circuit is connected to the seized trunk line to disconnect the operators telephone set therefrom.

9. A telephone system comprising trunk lines, an operators telephone set, a first subscribers line, means for connecting any one of said trunks with said first subscribers line, means operative when a trunk is so seized to connect the operators' telephone set thereto, means to indicate the seizure of a trunk, other subscribers lines, a link circuit for connecting with any one of said other subscribers lines, and means operative responsive to the connection of said link circuit to one of said other subscribers lines to connect the link circuit with the trunk line.

11. A telephone system comprising trunk lines, an operators position at one end of said trunks, a first subscribers line terminating at said position, an operators position at the other end of said trunks, means at the first mentioned operators position for connecting any one of said trunks, means operative when a trunk is seized to connect the sec-0nd mentioned operators telephone equipment thereto, means for indicating to the first mentioned operator when the second mentioned operators equipment is associated with the seized trunk, other subscribers lines, a link circuit at the second operators position for connecting with any one of. said other subscribers lines, and means operated responsive to the connection of said link fircuit to one of said other subscribers lines to connect the link circuit with said trunk 12. A telephone system comprising trunk lines, an operators position at one end of said trunks, an operators position at the other end of said trunks, means at the first mentioned operators position for seizing any one of said trunks, means operative when a trunk is seized for connecting the second mentioned operators telephone equipment thereto, a means operated in response to the connection of the second mentioned operators equipment to the seized trunk to transmit a momentary signal to the first lnentioned operators position over said seized trunk, subscribers lines, a link circuit for connecting with any one of said subscribers lines, and means operative when a trunk line and a subscribers line are seized to connect the link circuit with the trunk line.

15. A telephone system comprising trunk lines, an operators telephone set, means for seizing any one of said trunks, means operative when a trunk is seized to connect the operators telephone set thereto, subscribers lines, a link circuit for connecting with any one of said subscribers lines, means operative responsive to the seizure of said trunk line and said subscribers line to connect the link circuit with the trunk line, and means associated with the link circuit operative when the subscribers line is seized to indicate to the operator that the subscribers line is not otherwise engaged.

16. A telephone system comprising trunk lines, an operators telephone set, means for seizing any one of said trunks, means operative when a trunk is seized to connect the operators telephone set thereto, subscribers lines, a link circuit for connecting with any one of said subscribers lines, means operative when the trunk line and a subscribers line are seized to connect the link circuit with the trunk line, and a visual signal in said link circuit operated when a subscribers line is seized to indicate that the subscribers line is not otherwise engaged.

17. A telephone system, comprising trunk lines, an operators telephone set, means for seizing any one of said trunks, means operative when a trunk is seized to connect the operators telephone set thereto, subscribers lines, a link circuit for con necting with any one of said subscribers lines, means operative when the trunk line and a subscribers line are seized to connect the link circuit with the trunk line, and a visual signal in said link circuit operated when a subscribers line is seized and before the trunk line is connected to the link circuit.

19. A telephone system comprising trunk lines, an operators telephone set,

means for seizing any one of said trunks, means operative when a trunk is seized to connect the operators telephone set thereto, subscribers lines, a link circuit for connecting with any one of said subscr bers lines, means operative when the trunk line and a subscribers line are seized to connect the link circuit with the trunk line, means for disconnecting the link circuit from a trunk line when said trunk line is released, and a signal intermittently operated when the link circuit is released.

20. A telephone system comprising trunk lines, an operators telephone set, means for seizing any one of said trunks, means operative when a trunk is seized to connect the operators telephone set thereto, subscribers lines, a link circuit for connecting with any one of said subscribers lines, means operative when the trunk line and a subscribers line are seized to connect the link circuit with the trunk line, and an indicating means operative when the link circuit is disconnected from the subscribers line but still connected to the seized trunk line.

21. A telephone system comprising trunk lines, an operators telephone set, means for seizing any one of said trunks, means operative when a trunk is seized to connect the operators telephone set thereto, subscribers lines, a link circuit for connecting with any one of said subscribers lines, means operative when the trunk inc and a subscribers line are seized to connect the link circuit with the trunk line, and an intermittently operated signal actuated when the link'circuit is disconnected from the subscribers line but still connected to the seized trunk line.

22. A telephone system comprising trunk lines, an operators telephone set, means for seizing any one of said trunks, means operative when a trunk is seized to connect the operators telephone set thereto, subscribers lines, a link circuit for connecting with any one of said subscribers lines, means operative when the trunk line and a subscribers line are seized to connect the link circuit with the trunk line, and an intermittently operated visual signal actuated when the link circuit is disconnected from the subscribers line but still connected to the seized trunk line.

' 30. A telephone system comprising trunk lines, an operators telephone set,- means for seizing any one of said trunks, means operative when a trunk is seized to connect the operators telephone set thereto, subscribers lines, a link circuit for connecting with any one of said subscribers lines, means operative responsive to the connection of said link circuit to one of said subscribers lines to connect the link circuit with said trunk circuit, and means responsive thereto for automatically ringing the seized subscribers line.

32. A telephone system comprising trunk lines, an operators telephone set, means for seizing any one of said trunks, means operative when a trunk is seized to connect the operators set thereto, subscribers lines, a link circuit for connecting with any one of said subscribers lines, means operative when the trunk line and a subscribers line are seized to connect the link circuit with the trunk line, means for disconnecting the link circuit from the trunk line when it is no longer seized, and signaling means operative to give a distinctive signal indication when the link circuit is no longer connected to the trunk line and another distinctive signal when the subscriber on the connected subscribers line hangs up his receiver.

[Oflicial GazetteNovember 5, 1 9219.]

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