US1363268A - Telephone system - Google Patents

Description

Patented Dec. 28, 1920.

3 SHEETS-SHEET l- W. T. POWELL.

TELEPHONE SYSTEM.

APPLICATION FILED MAR.29, 1918.

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TELEPHONE SYSTEM.

APPLICATION FILED MAR.29,1918.

W. T. POWELL.

TELEPHONE SYSTEM.

APPLICATION. FILED MAR. 29. 1918.

1,363,268. 7 Patented Dec. 28, 1920.

3 SHEETSSHEET 3.

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UNITED STATES PATENT OFFICE.

WINFRED T. POWELL. OF EAST ORANGE, NEW JERSEY, ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. 'Y., A CORPORATION OF NEW YORK.

TELEPHONE SYSTEM.

Specification of Letters Patent. Patented Dec; 28, 1920.

Application filed March 29, 1918. Serial No. 225,444.

T 0 all whom. it 111 ay con 0cm Be it known that I, mrnno T. POWELL,

a citizen of the United States, residing at East Orange, in the county of Essex, 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 generally to telephone exchange systems, and more particularly to such systems wherein telephone connections between the subscribers lines are established and maintained by the agency of'automatic switching mechanism operated in response to the act'of initiating a call, together with directively operable switching mechanism actuated under the'control of the calling line and in response to electrical impulses transmitted thereover.

Telephone exchange systems whether of the full automatic or semi-automatic type may be briefly considered as consisting of two distinct classes, so far as concerns the method in which the preliminary switching operations involved in the establishment of a connection are effected automatically as a result of the usual act of removing the receiver from the switchhook upon the initiation of a call. In systems constituting one of these classes. it is the practice to have the telephone line of each subscriber to an exchange terminate in a line or individual switch. These switches are arranged to have access to trunk circuits leading to a plurality of selector switches and may be controlled by automatic devices in such a manner that the individual switch of each line when not in use is constantly maintained in operative relation to a trunk which leads to an idle selectorswitch. hen a subscriber, desiring to connect his line with the line of some other subscriber. removes his receiver from the hook, the line switch individual to his line. being thus prepositioned before an idle trunk, is instantaneously operated to connect his line directly through to a first selector switch; The subscriber may then begin to transmit impulses immediately after initiating the call with the assurance that such impulses will be properly directed to the circuit extending switching mechanism. While systems involving the use of individual switches possess the desirable feature of immediate connection to idle trunks, and the incident insurance against impulse mutilation, there is this undesirable factor to be considered, that a comparatively large number of switches are required.

In another class of automatic switching systems, above alluded to, the subscribers lines, instead of each being provided with an individual switch, are terminated in the multiple contacts of line finder switches. These finder switches may be arranged to serve vany one of a large number of calling lines. \Vhen a subscriber initiates a call, a condition is placed upon his line such that a finder having access thereto is set in operation to connect with the calling line and extend the same to an idle selector switch. After the finder has completed its function the calling party may then transmit impulses to selectively operate the selector switches in the proper manner. By the employment of finder switches, each serving a relatively large number of lines, it is evident that a considerable saving may be realized in the necessary amount of switching mechanism. But at the same time, the saving in the number of switches made possible by the use of line finders may only be had by sacrificing to some extent the desirable feature of immediate connection of calling lines to idle trunks. And there is therefore, the liability of switches being improperly operated as a result of the calling subscriber commencing to send out impulses before the finder has had time to complete its function. With the foregoing in view the present invention has as its general object the provision of an automatic telephone system, so constructed and arranged as to embody the advantageous features of the above described methods of switching calling lines into connection with idle trunk circuits, and at the same time one which practically eliminates the undesirable features of both.

Accordingly, this invention contemplates a system in which the subscribers lines are arranged to terminate in the multiple contact banks of finder switches, each switch serving a plurality of lines, and only a sufli cient number of finders being allotted to each grou of lines to handle the largest number 0 simultaneous calls originating in the group. Each line finder apportioned to a group of lines is permanently connected by means'of a link circuit to the movable contacts of a trunk finder switch, which latter switch is operable upon the initiation of a call in the group to which it is individual to Search out and make connection to an idle trunk circuit leading to a first selector switch.

Another feature consists in providing a single preselecting switch for each of the ductors of such line are instantaneously connected, by way of the movable contacts of the preselector switch serving such group, directly to the conductors of the particular idle first selector trunk which has previously been appropriated by said preselector switch.

Still another feature resides in the provision of means associated with the preselector, and responsive to the immediate extension of a connection therethrough to a preselected first selector trunk, to set in operation both a line finder and trunk finder switch. The line finder thus started in motion continues to operate until it has found the calling line, while the trunk finder continues to operate until it has found the particular first selector trunk to which the calling line is already connected by way of the preselector switch. Upon the establishment of this latter connection from a calling line to an idle trunk by means of a line finder and atrunk finder, means are automatically operated to disable the previously mentioned connection through the preselector switch, and such preselector immediately appropriates the next idle trunk ready for the next incoming call from the same line group.

Other and further features of invention will become more apparent after having considered the following detailed description.

In the drawings, Figures land 2 when taken together illustrate so much of a telephone system embodying the principles of this invention as is necessary to a clear understanding of the manner in which connections are extended and completed from one subscribers line to another; and Fig. 3

shows diagrammatically the manner of dividing the subscribers lines into groups, to-

- gether with the, line finders, trunk finders,

and the preselect'ing trunk switch allotted to each oup of lines.

Re erring to the drawings and especially to Fig. 3, a general description will first be given of a system involving the present invention, with particular reference to the division of lines into groups, the arrangement of the finder and preselector switches in each group, and the relation of the several line groups and their associated apparatus to a group of first selector trunks. The subscribers lines comprising the entire system may be divided up into a .number of major groups, all the lines of such a group being common to and having access through finder switches to the same group of first selector trunks. A portion of one of these major groups is illustrated in Fig. 3 and is shown to be subdivided into minor groups, there being only three such groups shown, while for simplicity the several subscribers lines of each subgroup are designated by the single conductors 300. The incoming subscribers lines 300 are terminated in the multiple stationary contacts of line finder switches 301. While but three lines are shown per subgroup it is evident that in practice there would be several lines, the capacity of the finders 301 being adapted to accommodate as many lines as is de- -sired to be collected in a subgroup. As will become more apparent hereinafter, by the novel arrangement of the present invention, it is possible to use single motion switches, and the finders 301 preferably are constructed to operate as simple rotary switches. Although the invention is not limited to any particular capacity of finder switches it will be assumed for clearness of illustration that the switches 301 serve twenty-five lines, which would mean that each subgroup of subscribers lines 300 contain twenty-five lines, as many finders 301 being provided as is necessary to give the requisite grade of service.

Each line finder 301 of a subgroup is permanently connected by a link circuit 302 to the movable contacts of a trunk finder switch 303. two movable contacts per switch are diagrammatically shown in Fig. 3, the lowermost contact of each switch cooperating with a series of stationary terminals which are each connected to a first selector trunk 304. These trunk finders are of the same construction as the line finders 301, being arranged to operate as single motion rotary switches, and having as many access points to first selector trunks as there are first selectors allotted to a major group of subscribers lines. As an arbitrary value it is assumed that twenty-five trunks 304, each leading to a first selector 305, will be sufiicient to serve a major group of lines comprising twelve subgroups of twenty-five subscribers lines each, three of which subgroups are shown in the drawing. Accordingly every subscribers line 300 of any of In the trunk finders 303 but the twelve subgroups may obtain connection through a line finder 301 and the associated trunk finder 303 to any of the group of first selector trunks 304, since the stationary terminals of the trunk finders 303 of each subgroup are multipled to the trunks 304.

For each subgroup of lines 300 and its associated line and trunk finder switches there is provided a single preselecting switch 306, of the same construction as the finder switches. The several lines 300 of a subgroup, as well as being terminated in the multiple terminalsof the finders 301, are also connected to the. armatures of individual line relays 307. The several front contacts of relays 307 of a subgroup are connected to a common circuit 308 which leads to the movable contacts or brushes of the preselector 306, which brushes are illustrated in Fig. 3 by the lower brush of the switch 306. The stationary terminals with which the preselector brushes connected to the common circuit 308 cotiperate, are connected as seen to the several trunks 304 in a manner corresponding to the multiplication of the stationary terminals of the trunk finders 303 to said trunks. The upper brush of the preselector 306 corresponds to the upper brushes shown for each of the trunk finder switches, the stationary terminals with which such brushes cooperate being multipled together throughout the sub roup. This multiplication of terminals of the trunk finder switches 303 and the preselector 306 within a subgroup serves, as will be more fully explained hereinafter, to control the extent of operation of a hunting finder switch 303 in accordance with the preselection of a trunk 304 by the preselector switch 306. It will also be clearly brought out in the following description how by the arrangement of the present invention the initiation of a call upon any line 300 of any subgroup, such line is immediately connected by means of its line relay 307, and the preselector switch 306, directly to the particular first selector trunk 304 that has previously been selected by said switch 306. And, moreover, it will be shown how the establishment of such a connection serves to initiate automatically the simultaneous operation of a line finder 301 and trunk finder 303, which switches remain in operation until the calling line 300 is connected by way of the link circuit 302 to the preselected trunk 304, whereupon the previously established temporary connection by way of the common circuit 308 becomes disabled.

Referring now to Figs. 1 and 2, a de tailed description will be given of the extension of a connection from one subscribers line to another; for which purpose it is assumed that the subscriber at substation 100 desires to converse with the subscriber at substation 200. On the removal of the -mary line relay. 103 individual to the line 104, 105: battery, through the upper windmg of relay 103, contact and lower armature of cutoff relay 106, line conductor 105, over the loop of substation 100, line conductor 104, upper armature and contact of relay 106 to ground. The relay 103, by energizing, establishes a circuit for itself in series with cutoff relay 106 and'a secondary line relay 107, which is likewise individual, to the calling line and corresponds to the line relays 307 shown in Fig. 3. This circuit may be followed from battery, winding of the stepping magnet 108, armature and contact of this magnet, back contact and lower armature of starting relay 109, conductor 110, contact 111 of relay 107, through the winding of said relay 107, lower winding, contact and armature of relay 103, winding of cutofl' relay 106, to ground. Magnet 108 is the stepping magnet for the preselector switch brushes 112,

113, 114, 115, diagrammatically shown at 303 in Fig. 3, and is so adjusted as not to operate in series with relays 106, 103 and 107. Relays 106 and 107., however, are energized in the circuit traced, and the relay 103 remains energized, although its initial circuit is opened by the cutoflf relay 106, with the result that the three said relays 106, 103 and 107 are now all looked up over a new circuit which leads from ground, winding of relay 106, armature, contact and lower winding of relay 103, through the winding, contact 111 and lower armature of relay. 107, to the conductor 116 common to all lines of the subgroup to which line 104, 105 belongs, and thence to battery.

-As soon as the secondary line relay 107 attracts its armatures in response to the initiation of the call, the two conductors 104 and 105 are connected directly to the trunk conductors 201 and 202 leading to the first selector switch shown in Fig. 2. This circuit, which may be traced as follows, is completed through the brushes 112, 113 of'the preselectori switch, such switch having selected the idle trunk 201, 202 prior to the initiation of the call: battery, through the upper winding of first selector line relay 203, back contact and inner upper armature of relay 204, trunk conductor 201, terminal 117 and brush 112 of the preselector switch, conductor 118, upper middle armature and contact of relay 107, line conductor 104, over the loop of substation 100, line conductor 105, upper lower armature and contact of relay 107, conductor 119, brush 113, terminal 120, trunk conductor 202, lower inner armature and back contact of relay 204, through the lower winding of relay 203, to ground. The line relay 203 energizes and the subscriber at substation 100 may immediately commence to send impulses over the circuit just traced to directively operate the first selector switch. However. it will first be supposed that the calling subscriber does not begin to operate his dial 121 until after suflicient time has elapsed for his line 104, 105 to be connected to the first selector trunk 201, 202 by way of line finder brushes 122, 123. 124, 125 and trunk finder brushes 126, 127,128 and 129..

' permost armature of relay 107, to ground.

Relay 109 energizes, and at itslower armature opens the circuit of-magnet 108 to prevent the same from operating due to the presence of a ground on the terminal 131, which is applied at this time over the conductor 205 from. the upper armature and contact of relay 206. The presence of this ground on terminal 131 will also be trans mitted to the corresponding terminals of preselector switches of all other subgroups of lines, having access to the group of trunks containing trunks 201, 202, since these terminals are multlipled 'throughout the several subgroups. ence, if apreselector in some other subgroup. happens to be standing upon the terminal corresponding to terminal 131, or, if, inhunting for an idle trunk, comes in contact with, such terminal it will be driven .away from this position by the completion of an operating circuit through its stepping magnet 108.

Relay 109 at its upper armature establishes a circuit for relay 152, which results in starting in operation the first idle line finder 122, 123, 124 125 and its associated trunk finder 126, 12 128, 129 of the group of such switches having access to the calling line. Said circuit leads from grounded battery, through the winding of relay 152, back contact and lowermost armature of relay 132, conductor 133, right-hand contact and upper armature of starting relay 109 to ground. Relay 152 completes the following circuit-for the stepping magnet 134 of the line finder switch which interrupts its own circuit and drives the brushes 122, 1 23, 124 and 125 over the terminals 135, 136, 137 and 138 of the line of the group containing the calling line; battery, contact and inner armature of relay 152, through the winding, armature and contact of magnet 134, finder test brush 125, and thence to the terminal 138, back contacts and uppermost armatures of relays 107 of all non-calling lines in the group over which the test brush 1'25 moves. Vhen, however, the brush 125 finds the ter minal 138 of the calling line, the relay 107 thereof being energized as described. no ground will be present on such terminal and consequently magnet 134 will come to rest with the finder brushes positioned on the terminals of the calling line 104, 105.

At the same time the relay 152 at its lowerarmature establishes an operating circuit for the stepping magnet 151, which interrupts its own circuit and operates to drive the brushes 126, 127, 128 and 129 of the trunk finder associated with the line finder already started in operation, over the terminals 149,' 150, 139 and 140 of first selector trunks in search of the particular trunk to which the calling line 104, 105 is already connected by way of the preselector brushes 112 .and 113 as above explained. The circuit for magnet 151 is traceable from free pole of battery, resistance 141, through the Winding of 'magnet 151, armature and contact thereof, contact and lower armature of relay 152 to ground. The contacts 140 corresponding to all trunks of the group of first selector trunks, other than the trunk .201, 202 upon the corresponding terminal 142 of which the preselector brush 115 is now standing, are free from ground connections. This is true since the terminals 140 of each of the trunk finders in the subgroup are multipled to the conductor 143, which leads to the terminal 142 only of the preselector switch individual to such subgroup, and-is not multipled to preselector switches in other subgroups. Therefore, since the brush 115 can stand on but one terminal 142 at a time, and as already observed said brush is now positioned upon the terminal 142-which corresponds to the selected trunk 201, 202, the trunk finder brush 129 in its movement over the terminals 140 of all other trunks will fail to find a ground connection thereon. But when stepping magnet 151 moves the brush 129 onto the terminal 140 of the preselected trunk 201, 202, the following circuit is established to dis continue the operation of said magnet, thereby bringing the trunk finder brushes 126, 127, 128 and 129 to rest upon the proper set of terminals 149, 150, 139 and 140: battery, resistance 141, through the winding of low resistance relay 144, brush 129, terminal 140, conductor 143, terminal 142, brush 115, left-hand contact and upper armature of relay 109, to ground. The resistance of relay 144 being low in comparison with that of magnet 151, battery current is shunted around the stepping magnet in the circuit just traced, and said magnet ceases to operate. Relay 144, however, energizes and closes a circuit from battery, contact and inner armature of ,relay 152, through the winding, armature and contact of magnet 134, conductor 145, lower winding of relay 132, middle armature and contact of relay 144, to ground. It Wlll be observed that this circuit is in parallel to the previously traced circuit for the line finder magnet 134 which leads to ground at the back contact and upper armature of relay 107 of all lines encountered by the brush 125 prior to its arrival on the terminal 138 'of the calling line. If then the trunk finder finds the preselected trunk, and the above traced circuit is completed for relay 132 before the line finder has completed its function, said relay does not operate by reason of a direct ground being placed upon conductor 145 at the upper armature and back contact of relays similar to relay 107. But when the llne finder 122, 123, 124, 125 has found the calling line, andground is removed from conductor 145, relay 132 receives sufficient current to energize.

The attraction of the upper armatures of relay 132 completes the connection from the calling line through the line finder and trunk finder switches to the line relay 203 of the selected first selector switch. This circuit-may be traced from battery, through the upper winding of relay 203, back con tact and-inner upper armature of relay 204, conductor 201, terminal 149, brush 126, contact and uppermost armature of relay 132, brush 122, terminal 135, line conductor 104, over the loop of substation 100, line conductor 105, terminal 136, brush 123, inner upper armature and contact of relay 132, brush 127,. terminal 150, conductor 202, inner lower armature and back contact ofrelay 204, lower winding of relay 203, to ground. The relay 203, which is already energized over the previously described cir cuit completed at the time the call was initiated, remains energized in this new circuit just traced after the interruption of its first operating circuit, which interruption, as will presently be seen, soon takes place. \Vhen relay 203 first operated, it closed a circuit for slow releasing relay 206 from battery through the winding of such relay, to ground at the front contact and armature of relay 203. Returning to the relay 132, the energization thereof also closes the following circuit: battery, contact and inner upper armature of slow relay 206, conductor 207, terminal 139, brush 128, contact and inner lower armature of relay 132, through the upper Winding of relay 132, brush 124, terminal 137, conductor 146, winding of relay 106, to ground. The application of battery to the conductor 146 shunts out the line relays 103 and 107,

p which up to this time have been held up in series with cutofi' relay 106. Relays 103 and 107 thereupon deenergize, while the cutoff relay 106 remains operated in the circuit traced to prevent the repetition of the calling condition at the preselector switch. As soon as relay 107 reacts, the temporar 1ly extended connection from the calling llne 104, 105 over conductors 118 and 119 to the trunk 201, 202 is opened, and the line is now connected through to the selector only by way of the finder switches. The upper armature of relay 107 in retracting opens at its first front contact the circuit of starting relay 109, and at its back contact places a ground upon terminal 138 of other line finders of the group to render the line 104, 105 non-calling. The presence of a ground on terminal 138 of the operated finder does not cause any further movement thereof at this time since the circuit of magnet 134 has already been opened by relay 152, which relay deenergized upon the operation of relay 132. The retraction of the arinatures of relay 109 closes the fol lowing circuit for the stepping magnet 108 of the preselector switch 112, 113, 114, 115: battery, through the winding of such mag- .net armature and contact thereof, back contact and lower armature of relay 109, brush 114, terminal 131, conductor 205, uppermost armature and contact of relay 206 to ground. Stepping magnet 108' operates and steps the brushes 112, 113, 114 and 115 of the preselector onto the, terminals of the next first selector trunk in the group. If such trunk happens to be busy there will be a ground on terminal 131 corresponding thereto, and the preselector is moved over a second step.- This operation continues until an idle trunk is located, whereupon the preselector'is arrested and awaits in readiness for the next call of its individual subgroup of lines. Upon the initiation of a second call on another line in the same subgroup of lines, the secondary line relay,

lay 109, conductor 133, lowermost armature and front contact of relay 109, conductor 133, lowermost armature and front contact of relay 132, inner armature and contact of relay 144, now denergized, outstarter wire 148, to the next idle line finder and its associated trunk finder switch in the group.

The calling line 104, 105 having thus been extended through to the first selector switch, the calling subscriber, who as originally assumed does not begin to send out impulses until the finder switches have had time to find his line, now manipulates the dial 121 to directively operate the first selector switch in accordance 'with the first digit of the called number. For each interruption of the line by the sender 121 the line relay 203 retracts its armature. At the first retraction of the armature of said relay the following circuit is closed: grounded armature and back contact of relay 203, lowermost armature of relay 204, lower armature and front contact of slow relay 206, through the winding of relay 208, winding of primary stepping magnet 209, to battery. The primary magnet 209 operates and steps the first selector brushes 210,211 and 212 up one step into operative relation to the first level of trunks. For each succeeding retraction of the armature of relay 203 magnet 209 advances the brushes 210, 211 and 212 one step, and finally at the termination of the series of impulses brin s them to rest opposite the desired level of trunk terminals. On the f,

:st vertical step of the brush shaft (not s'h"'wn) the primary ofinormal contact 213 is closed. Relays 208 and 206 being slow to releasehold their armatures attracted during/the operation of magnet 209 with the result that the following circuit is established as soon as the olf-normal contact 213 is closed: free pole of battery, through the winding of relay 214, off-normal contact 213; front contact and armature of relay 208; upper armature and contact of relay 206 to ground. Relay 214 energizes in this circuit and closes another circuit for itself independent of the contact of relay 208, which may be traced from battery, winding of relay 214, off-normalcontact 213, conductor 215, armature and contact of the secondary stepping magnet 216, to ground at the upper armature and contact of relay 214.

At the end of the primary series of impulses, and after rela 203 remains energized for a suflicient perio relay 208 releases its armature to close a circult from battery, through winding of secondary magnet 216,

inner armature and contact of relay 214,

back contact and armature of relay 208, to

' ground at the upper armature and contact of relay 206. The magnet 216 energizes in this circuit and operates in the wellknown manner to rotate brushes 210, 211, 212 into en agement with the first set of terminals 21 218, 219 in the selected level. Magnet 216 by attracting its armature also opens the above traced circuit for relay 214, causing said relay to become .deenergized. Relay 214' on .retracting its armatures in turn opens the circuit of the magnet 216, which thereupon deenergizes, preparatory to giving the brushes 210, 211, 213 a second step forward. If the first trunk in the group is busy this condition will be manifested by the presence of a ground upon the test terminal 219 thereof. As soon, there-' fore, as the magnet 216 deenergizes after having imparted its first step to the brushes 217, 218, 219, a circuit is closed as follows to again energize the relay 214: battery, winding of relay 214, contact 213, conductor 215, armature and contact of magnet 216,

conductor 220, back contact and upper armature of relay 204, conductor 221, brush 212,

ceeds, the relay 214 being successively energized at the end of each step by ground connections on the test terminals of busy trunks, until brushes 210, 211, 212 arrive upon the terminals 217, 218, 219 of an idle trunk leading to the next switch.

It is to be noted that while the switch is in its secondary movement each time a circuit is completed. for relay 214 a parallel circuit is also\established including relays 214 and 204 in series. able from'battery, winding of relay 214, contact 213, conductor 215, armature and contact of magnet 216, conductor 220, winding of relay 204, to ground at the up er armature and contact of relay 206. wever, during the hunting operation of th'%itch the relay 214 is energlzed by a circuit ich leads, as above described, directly to he grounded test wire 221, and the relay 204 ing shunted thereby does not actuate at th s time. But as soon as the hunting movemen is completed brush 212 stands ona, non l grounded terminal 219, and relays 214' and\100 This circuit is trace- 7 204 are connected in series with each other in the circuit .just traced. -Relays 214 and 204 are so constructed that when laced in series with each other relay 204 receives sufficient current to operate, while relay 214 remains inert. The attraction of the armatures of relay 204 disconnects the trunk conductors 201 and 202 from the selector line cuit for relay 204 until the connector line I relay (not shown) has had time to operate and place a ground back upon the test wire 221 in awell-lgnownmanner. With a ground on wire 221' the relay 204 is held energized from battery, through the winding of relay- 214, contact 213, conductor 215, armature and contact of magnet 216, conductor 220,

winding of relay 204, front contact and uppermost armature of relay 204, to the grounded test Wire 221. The ground conneetion applied to conductor 221 from the connector switch is also transmitted by way of the uppermost armature and front contact of relay 204 and conductor 205 to the multiple terminals 131 of all preselector switches to substitute for the ground at the ll hen slow relay 206 deenergizes, it removes battery from conductor 207 at its inner upper armature, but relays 132 and 106 are maintained energized by the application of battery current to conductor 207 at the primary off-normal contact 227.

The calling subscriber may now operate his dial 121 to transmit the tens and units series of impulses, which are effective to step the connector brushes 224, 225, 226 into en-. gagement with the terminals 228, 229, 230 of the called line 200.

At the termination of conversation when the subscribers have replaced their receivers on switchhook, the connector restores and removes ground from the test wire 221. Removal of ground from said testwire causes the deenergization of relay 204, which completes the following circuit for the selector release magnet 231: battery, winding of magnet 231, primary ofi-normal contact 232, back contact and lower armature of relay 206, lower armature and contact of relay 204, back contact and armature of relay 203, to ground. After the selector switch is completely restored by release magnet 231, the primary off-normal contact 227 is opened to'remove battery from conductor 207. Relays 132 and 106 thereupon release, the former of which opens the link circuit between the line finder and trunk finder used in extending the call, and also connects the starter WlI' 133 to the relay 152. while the cutoff relay 106 places the line 10-1, 105 in its normal condition. Ground is also removed I from conductor 205 so that the first selector trunk 201, 202 again becomes available to the preselector switch 112, 113, 114, 115 of any subgroup of lines. All apparatus involved in the extension of the connection is now in its idle condition and may again be taken for use. The line finder 122,123, 124:, 125 and trunk finder 126, 127, 128, 129, which as explained are simple rotary switches,'do not return to a normal position at the end of each call but remain in the position last used ready to be operated when the next call comes in.

From the above description of the novel arrangementv employed for automatically switching calling lines into connection with idle trunks, it is obvious that the calling subscriber after having initiated the call may immediately begin to send out impulses to operate a first selector switch. Assume then that the subscriber at substation 100, after having removed his receiver from the hook, commences at once to manipulate the dial 121. As was previously explained the removal of the receiver from the hook causes the energization of secondary line relay 107,

pper armature and contact of relay 206.

which connects the line 104, 105 directly to the preselected idle trunk 201, 202 by way of the preselector brushes 112 and 113. Operation of the dial 121 therefore causes the selector line relay 203 to vibrate in the usual manner to actuate the brushes 210, 211, 212 to the proper group of trunks. In the meantime the line finder 122, 123, 12 1. 125 and trunk finder 126, 127, 128, 129 are started in operation, as has been clearly explained, and continue their hunting movement until the calling line 104, 105 is connected by way of these switches to the selected trunk 201, 202. In case the finder switches should complete their operation during the time the subscriber is sending impulsesato the first selector by way of the preselector switch there is no liability of mutilating such impulses since the temporarily established circuit through the preselector is not interrupted until after the permanent connection to the first selector trunk is completed by the finder switches. X

What is claimed is:

1. In a telephone system, a telephone line, a trunk circuit, relays responsive to the initiation of a call on said line for establishing a connection between said line and trunk circuit, and means also responsive to the initiatlon of said call for establishing a second connection between said line and trunk circuit.

2. In a telephone system, a line, a trunk circuit, a relay for connecting said line to said trunk circuit, and means operated upon the completion of such connection for establishing a second connection between said line and trunk circuit.

3. In a telephone system, a telephone line,

a trunk circuit, relays for establishing a connection between said line and trunk circuit, means operated upon the completion of such connection for establishing a second connection between said line and trunk circuit, and means operated upon the completion of said second connection for disestablishin said first connection.

4. 1% a telephone system, a telephone line,

a primary and a secondary line relay therefor, a trunk circuit, means responsive to the initiation of a call on said line for establishing a plurality of separate connections between said line and trunk circuit, one of said connections being immediately established upon the energization of said line relays, and means operated when all of said connections have been completed for disestablishing one of said connections.

5. In a telephone system, a line, a trunk circuit, relays responsive to the initiation A trunk circuit, means operated upon the comtiation of said call for starting the operation of said switches.

6. In a telephone system, a line, a trunk circuit, means for establishing a connection between said line and trunk circuit, automatic switches for establishing a second conpletionof said first connection for starting the operation of said switches, and means operated upon the completion of the movement of said switches for disestablishing said first connection.

- In a telephone system,'a telephone line. trunk circuit, means operative to establ sh a connection between said line and trunk circuit, a plurality of automatic switches for establishing a second connection between said line and trunk circuit, and means operated upon the establishment of said first connection for starting simultaneously the operation of said automatic switches.

' 9. In a telephone system, a telephone line,

a trunk circuit, means operative to establish a connection between said line and trunk circuit, a plurality of automatic switches for establishing a second connection between. said line and-trunk circuit, means operated upon the establishment of said first connection for starting simultaneously the operation of said automatic switches, and means operated when all of said switches have completed their movement to disestablish said first connection. f

10. In a telephone system, a telephone line,

' a trunk circuit, relays responsive to the initiation of a call on said line for establishing a connection between said line and trunk circuit, an automatic switch also responsive to the initiation of said call for establishing a second connection between said line and trunk circuit, and means operated when said switch has completed its movement to disestablish said first connection.

11. In a telephone system, a line, a trunk circuit, link circuits for interconnecting said inc and trunk circuit, means responsive to the initiation of a call upon said line for immediately effecting a connection between said line and trunk circuit over one of said link circuits, a finder switch, and means also responsive to the initiation of said call for operating said finder ,to connect said line to said trunk circuit over another of said link circuits.

12. In a telephone system, a line, a trunk circuit, link circuits for interconnecting said immediately eifecting a means responsive to upon said line for connection between said line and trunk circuit over one of said link circuits, finder switches, and means operated upon the establishment of said connection for starting one of said switches in operation to find said line and for starting another-of said switches in operation to find said trunk circuit to establish a second conline and trunk circuit, the initiation of a call nection between said line and trunk circuit over another of said link circuits.

13. In a telephone system, a line, a trunk circuit, link circuits for interconnecting said line and trunk circuit, means responsive to the initiation of a call on said line for immediately establishing a connection between said line and trunk circuit ,over one of sald link circiiits, means also responsive to the initiation of such call for establishing a second connection between said line and trunk circuit over another of said link circuits, and ase'nder associated with the call ing line for transmitting impulses to said trunk over either-of said link circuits.

14. In a telephone system, a line, a trunk circuit, link circuits for interconnecting said line and trunk circuit, relays responsive to the initiation of a call on said line for establishing a connection between said line and trunk circuit over one of' 'said link circuits, means operated upon the completion of such connection for establishing a second connection between said line and trunk circult over another of said link circuits, means operated upon the completion of such second connection for disestablishing said first connection, with said line for sending impulses to said trunk over either of said link circuits.

15. In a telephone system, a line, a trunk terminating in a selective switch, link circuitsfor interconnecting said line and trunk, relays responsive to the initiation of a call on said line forestablishing a connection between said line and trunk over one of said link circuits, finder switches, means operated upon the completion of said connection for starting the finder switchesin operation to establish a second connection between said line and trunk over a second one of said link circuits, and acalling device associated with the calling line for sending impulses over said first link circuit to .the selective switch while said finder switches are in operation and for sending impulses over said second link circuit to the selective switch after the finders have completed their operation.

16. In a telephone system, a plurality of lines, a plurality of trunks, link circuits for interconnecting said lines and trunks, means operated in response to .the initiation of a call on one of said lines to connect such line to an idle one of said trunks over one of said link circuits, finder switches, means operand a calling device associated ated in response to the initiation of said call for starting one of said finders in operation to find the calling line and for starting another finder in operation to find said idle trunk, to establish a second connection between said line and idle trunk over another of said link circuits, and means for preselecting idle trunks.

17. In a telephone system, a plurality of lines, a group of trunks, link circuits for interconnecting said lines and trunks, means operative to connect a calling line to an idle one of said trunks over one of said link circuits, finder switches, means controlled in the establishment of said connection for starting one of said switches in operation to find the calling line and for starting another of the switches in operation to find said idle trunk, to establish a second connection between said line and idle trunk over another of said link circuits, means controlled in the establishment of the connection over said second link circuit for disestablishing the connection over said first link circuit, and means for preselecting idle trunks in said group.

18. In a telephone system, a plurality of lines, a group of trunks, a preselector switch for preselecting idle trunks in said group, a

ing line and for starting said trunk finder selector switch to preselect the next idle trunk in the group.

19. In a telephone system, a plurality of groups of lines, a group of trunks for serving said lines, a connecting circuit for each group of lines including a preselector switch arranged to preselect idle trunks in said group, a plurality of link circuits for each group of lines each including a line finder and a trunk finder, means operated upon the initiation of a call on any line in any group for connecting said line to a preselected idle trunk over the connecting circuit individual to such group of lines, means controlled in the establishment of such connection for starting the operation or the line finder and trunk finder included in an idle link circuit individual to the group containing the calling line, said line finder operating to find the calling line and said trunk finder operating to find said preselected trunk to thereby connect said calling line to the preselected trunk over said idle link circuit, means operated to thereupon disestablish the connection over said connecting circuit and to operate the preselector switch to preselect the next idle trunk in the group.

In witness whereof, I hereunto subscribe my name this 25th day of March A. D., 1918.

WINFRED '1. POWELL.

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