US1574873A - Telephone-exchange system - Google Patents

Description

March 2 1926.

G. DEAKIN TELEPHONE EXCHANGE SYSTEM 4 Sheets-Sheet 1 Filed Feb. 25, 1922 w WHTNQ Mmh 2,1926. 1,574,873

6- DEAKIN TELEPHONE EXCHANGE SYSTEM Filed Feb. 25, 1922 4 Sheets-Sheet 2 March 2 1926.

G. DEAKIN TELEPHONE EXCHANGE SYSTEM Filed Feb. 25, 1922 4 Sheets-Sheet 5 nun-um Gonna-nun "nun-"Hun" Dunn Dunn-Dunn" wk g .m m w w m w BIT w HM; nwwwi .QNJT J g ATH wmr P r M H H g M .l? RAN sow 1,574,873 G DEAKIN TELEPHONE EXCHANGE SYSTEM Filed Feb. 25, 1922 4 Sheets-Sheet 4 March 2 1926.

n I. i. m .i deemed Mar, in,

easier rel cs.

GERALD DEAKIl-I, 0F ANTVVERP, BELGIUM, ASSZGNOR TO WESTERN ELECTRIC GOM- PANY, INCURPGRATED, 9F NEW YORK, ll. EL, A CORPORATION OF NEW YORK.

TELEPHONE-EXCHANGE SYSTEM;

Application filed February 25, 1922. Serial No. 539,121.

To all whom it may concern:

Be it known that l, GERALD DEAKIN, a citizen of the United States, residing at Antwerp, Belgium, have invented certain new and useful Improvements in Telephone- Exchange Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to telephone exchange systems and more especially to systems wherein automatic switching apparatus is employed for the extension of talk-- ing connections.

Where automatic switches, such as finder switches, are utilized for seizing and extending subscribers lines either to succeeding selective switches or to operators positions, a convenient way of handling calls incoming on the subscribers lines is to divide said lines into groups and to assign the proper number of finder switches to serve each such group of lines. It the capacity of the automatic switches is sufilciently large it is advantageous to provide each switch with a plurality 01" sets of brushes, each set of brushes having access to a smaller group of lines. By this arrangement only the particular brush set having access to the group of lines containing the calling line need be taken for use.

In order to materially reduce the operating time it is proposed to divide each brush group into two sub-groups and to connect the lines to the terminal banks such, that one sub-group of lines appears as first choice lines to the brushes 0t halt of the finders and second. choice lines to the brushes of the remaining finders. Likewise, the second sub-group 0t lines appears as first choice lines to the second half of the finder switches and as second choice lines to the first half of the finder switches. Normally, when a call originates in one of the sub-groups a switch having access as first choice to this subgroup is taken for use. Hence, the switch is only required to move over the first half ot the group served by its brushes. When all finders having access to a sub-group as first choice are engaged at the time a call is originated in that sub-group, one of the finders having second choice access to this particular sub-group is set in operation to make connection with the callin line, provided one of these latter finders is idle at the time.

The selection of the set of: brushes of an idle finder switch having access to the group of lines containing the callingline may be accomplished under the control of registers upon which the identity of the calling line has been placed in response to the act of initiating a call. According to this plan the finder switch is operated directively in its brush selecting movement under the control of the registers. After the set of brushes has been selected and rendered effective, the

"further movement of the switch, which may take place automatically, causes the set of brushes to make connection with the terminals of the calling line.

. The object of the invention is to provide, in a system of the above described character wheretwo groups of lines are respectively served by two groups of automatic switches as first choice, each group of lines being served by the other group of switches as second choice, for directively operating any one of said automatic switches to make connection with a line.

A feature of the, invention relates to the provision of means for operating an automatic switch in either group directively in accordance with the identity of a calling line for making connection with such line.

A further feature relates to the provision of meansrfor taking a record on register devices of the calling line identity and for directively operating an idle one'ot said antomatic switches in either group in accordance with said, record to make connection with the calling line.

A still further feature of the invention relates to the provision of an arrangement wherein an automatic switch in the group serving a calling line as first choice is operated directively to select such line, and wherein it all switches of the group serving the calling line as first choice are busy an automatic switch in the other group is operated directively to choose the calling line.

Such other and further features as are contemplated by the present invention will become more apparent from a consideration of the following detailed description and also from the appended claims.

Referring particularly to the drawing, Figs. 1, 2, 3 and 4., when arranged with Fig. 2 below Fig. 1 Fig. 3 below Fig. 2 and Fig. 4 to the right of Fig. 1, illustrate a portion of a telephone exchange system embodying the principles of the present invention.

Fig. 1 shows one of a plurality of subscribe-rs lines terminating -at-the central office in the "terminal bank of an automatic or line finder switch. This figure also shows the details of the automatic "finder switch which, together with a second automatic switch hereinafter known as a cord selector switch, seen at the right of the figu-re, com- ;prises one of a plurality of switching units serving to extend subscribers lanes to operators positions.

@Fig. 2 at the left of theleft-hand vertical broken line shows a plurality out line relays arranged in groups, each relay being individual to a subscribefs line. Between the two vertical broken lines in this figure there are shown ltWQ EEUllOtt-Bl switches one :for each of two different groups of finder switches and also certain common controlling equipment. To the right of the right hand vertical broken line in Fig. 2 there is shown certain common devices for rendering the allotters inefiective in response to certain conditions among the :groups of cords at the operators positions.

'8 shows :a portion of the register -re lays Ito-getherwith a part of a set otcounting relays for controlling the directive movement of the automatic switches.

4 shows one of a plurality of cord circuits which leads from the terminals of the cord selector switches shown in Fig. 1

and terminates in a plug at the operators position. There as also shown the super .visory signals and cont-rolling equipmentindivi-d-nal to this cord. Moreover, this figure illustrates a common operators .seleoting switch, the operators talking equipment, and other devices .at the position common to all cord circuits handled by that particular operator.

5 is a schematic illustration showing .how the subscribers lines are divided into groups to appear in the biinks of the line finder switches as first choice with respect to certain of the finders and as second choice with respect to other finders.

General description of the system and apparatus.

It believed that .a comprehensive understanding of the invention will be greatly facilitated by first giving a general layout of the system showing how the lines are divided into groups and in what manner .scribers lines are divided .into groups of switches.

200 lines each, a group of 200 lines appearing in the terminals of the finder switch at the central ofiice, such as the switch 190, shown in Fig. 1, and also illustrated in Fig.

These finder switches are of the wellknown rotary power driven type having a bank of 200 terminals arranged in ten different levels, there being twenty lines to av level. The ten sets of brushes, one for each level, are mounted on a brush carriage and are selectively chosen and tripped by means of a trip spindle mechanism so as to make contact with the terminals of the level when the brush carriage is rotated under the control of a power device. The structure of .a. switch of this character is illustrated in general in the patent to McBerty, 1,097,868, issued May 26, 1914.

In order to enable a desired number of simultaneous connections, a group of 200 lines will he provided with a suitable number of line finder switches at the central office. When one switch is busy and .a call. occurs in the group of 200 lines, another switch maybe taken for use, and so on until all the switches are busy, at which time further calls will be obliged to wait until a switch becomes idle. Owing to the large capacity of the switch it- .is found that a considerable amount of time would be necessary for .a set "of brushes to hunt over an entire level of twenty terminals to choose a calling line. This hunting time is greatly reduced by a plan of division and distribution =ol lines about to be described. The total group of 200 lines may be divided into two groups of 100 lines each, meaning that each level of twenty lines in the finder bank (see Fig. is divided into two halves. Each level, when thus divided, constitutes two separate groups of ten terminals each, the first ten terminals and the second ten ter minals. In Fig. 5 the division is illustrated by the vertical broken line. In conformity with the division of each level of terminals into two subgroups of ten terminals each, the finder switches themselves .are also divided into two groups. These will be referred to hereinafter and are designated in Fig. 5 as the A and 13 groups of finder That is to say, half of the finder switches are segregated in one group and known as the A group of switches, one of which is shown in Fig. 5 at the left, while the other half of the finder switches, known as the B group, are similarlyarranged. One of these switches is shown in Fig. 5 at the right. In correspondence with this method of dividing the finder switches up into two groups, thesubscribers" lines served by these switches are also arranged in two different groups. The first 100 subscribers lines, known as the A subgroup of lines, appear in the first half of the terminal bank ot-all the A finder switches. For example, lines 500 and 501 are two of the A lines and are seen to appear in terminals 502 and 503 of the first half of the level of terminals served by the brush A. The remaining eight lines of the A subgroup appearing in this level will be similarly connected. Furthermore, all the remaining lines of the 100 group of A lines will occur in the terminals of the other nine levels served by the A finders as first choice. In addition to appearing as first choice before all of the A finders the A lines, such as 500 and 501, are multipled and appear in the terminals of all of the B finder switches. Their appearance in the B finder switches, however, is as asecond choice. That is to say, they appear in the second ten terminals of the corresponding levels. The line 500 appears in terminals 505 and line 501 in terminals 506, both of which correspond to the terminals 502 and 503 of the A finders but are in the second half of the bank. These lines would be served by the brush 507 not as first choice but as second choice, brush 507 first traversing the entire set of ten terminals of the first half of the level before it can encounter the terminals of the lines 500 and 501 in the second half of the level.

In an analogous manner the remaining group of subscribers lines, known as the B group, two of which are shown as lines 508 and 509, appear as first choice lines in all of the B finder switches and as second choice lines in all of the A finder switches. Lines 508 and 509 appear in terminals 510 andterminals 511 in the first half of the bank of all B finder switches, and are also inultipled to appear in terminals 512 and terminals 513 of the corresponding level but in the second half thereof with respect to the A line finder switches.

As will hereinafter be explained, the circuit arrangement is such that in the normal operation, whenever a call occurs on one of the lines of the A group, an idle one of the A finder switches normally serving said lines as first choice is started in operation to make connection with the calling line. Similarly, whenever a line occurring in the B group of subscribers lines originates a call at a time when there is in the B group of finder switches an idle one, then this switch is set in operation to extend the calling subscribers line. However, should one of the A subscribers lines originate a call at a time when all of the A finder switches are busy, one of the B finder switches, if one be idle, is taken for use and operated to find the calling line in the A group. Conversely, the same is true with respect to the operation of an A finder switch to serve one of the B lines when the call is initiated when all of the B finders are busy but there is an idle one of the A finders.

Where each finder switch has a plurality of brushes one of these brushes, namely the one having access to the level of lines containing the calling line, must be selected and rendered effective. To accomplish this purpose there is provided a register mechanism consisting of a plurality of relays shown at the left in Fig. 3.' These relays are responsive to the initiation of a call to set up a record identifying the particular level of terminals in which the calling line appears. That is to say, if the calling line is one belonging to the first level of finder switches then the relays 210 and 214 are energized and indicate that the calling line is one of the twenty lines occurring in the first level of terminals before all the switches. If the line originatingthe call appears in the second level then the register relays 211 and 215 are operated. If the calling line is one appearing in the third. level the relays 212 and 210 are operated, and so on for each of the ten different levels of lines. The record having been established on the register relays the allotted line fi-ndier unit in the proper group is started in operation and is controlled directively by means of a controlling circuit and a set of counting relays shown in Fig. 3 in accordance with the identity of the line as recorded on the register relays. When the switch has operated in its brush tripping movement through a. distance coinmensurate with the identity of the calling line, the controlling cicuit is rendered ineffective and the operation ceases. Fol: lowing the brush selecting operation the regular hunting movement of the switch. oc ours and the chosen set of brushes is caused to hunt over the terminals until the calling line is found, thereby extending the connection through to a cord selector switch 180 shown at the right of Fig. 1.

The cord selector switch, which is assumed to be a small rotary switch having a capacity of twenty sets of terminals, is started in movement and hunts over the terminals representing cords leading to the operators position. N hen an idle cord is reached the cord selector switch stops and the calling line is thus extended through to the operators cord circuit and she is given the proper notification as to the identity of the cord chosen.

The operators equipment is connected to the chosen cord circuit, as illustrated in Fig. 4, by means of a selecting switch which is common to a number of cord circuits. After being connected to the cord circuit she may communicate with the calling subscriber to obtain the information necessary for her to complete the call or for extending it on to other operators.

The finder switches of the A group are allotted for use by means of an allotter switch 201, which has .a plurality of positions one for each of the difierent switches it controls. In alike manner the finder switches of the B group are allotted :for use by means of the allotter switch 200. The .allotter switches 201, 200 and the control switches 1-00, 300and 220 are of the sequence switch type well-known in the art and corresponding in construction and operation to that shown in the patent to Reynolds and Baldwin, No. 1,127,808, issued Fehruary .9, 1915.

driven device similar in principle to the finder switch 190, except that it is only equipped with a single set of brushes. lhe

power magnet for operating the brush carriage of the switch 180 is indicated by the character 125.

Detailed operation of the system.

Initiation of a cell in the ./l group of Yin-cs when one 0; the A finders aouZaMe.-lt will he assumed that the subscriber of line :501, which occurs in the A group and in the third level o1 terminals in the finder switches, initiates a callat a time when some one of the it finder switches, normally serving this line as first choice, is idle. The subscriber, upon removing his receiver from the switchhook, completes a circuit from hattery through the winding of line relay 205, outermost hack contact of relay 112, over the loop of the calling line d returning by try of the middle contact of relay 112 to ground. The line relay 205 becomes energized and completes a path from battery through the winding of relay 112, right contact oi relay 205 :to the test terminal 1151 of the subscribers line in all the A and l3 finder switches serving said line. This potential applied to the test terminal serves as an identification ol' theca lling condition of the line.

F urthermore, the line relay 205, on operating, completes a circuit traceable from loat- 'tery :through the inalcehe'l ore-hreak contacts .at the outer arinatur s of register relays 214, 215, 216 and through corresponding contacts of all the remaining register relays not shown in this disclosure (the series cir cuit through the relays not shown being indicated schematically by the broken conductor), conductor 251, inner back contact of :relay 216, winding of said relay, winding .of :relay 212, conductor 252, key 253, conductor 25 1, left contact of relay 205, key 255, left contact of relay 223, winding of relay 209, left back contact of relay 208 to ground. Relay 216 energizes in this circuit and its contacts are so arranged that its inner arma-t .re makes engagement with he front contact before the make-before-hrealr contact at the outer armature is opened. By this arrangements circuit is immediately The cord selector switch 180 is a power closed which leads from battery, as above traced, through the make-heforohrealr contacts of relays 21%, 215, through the outer armature and contact of relay 216, winding of said relay, and thence through the windings of relays 212 and 209 to ground. Helays 212 and 209 also become energized in series with the relay 216.

Relay 216, upon energizing, opens the series circuit at its make-before-break contact such that if another line in any other level initiates a call the corresponding register relays 21%, 215, etc, cannot be operated. That is, as soon as one line in the group of 200 lines succeeds in initiating a call, all other lines in the same group are barred from initiating calls until a switch is started to find the first calling line and the proper set of brushes trippedand the corresponding register relay released to restore the closed condition of the series circuit. This, of course, requires only a slight interval 01" time.

Relay 216, upon energizing, also completes a circuit from battery through the makehe'tere-h-reak contacts of relays 211- and 215, outer arn'iature and front contact of relay 216, inner armature and front contact or" said relay,conductor 250, windings of relays 219 and 221 to ground. These relays operate and serve to supply locking circuits for the counting relays, as will appear hereinafter.

clay 209, which it will he renien'ihered also energized in series with the register relays 216 and 212, at its left back contact opens the energizing circuit of relay 208 whereby this latter relay is prevented from being energized so long as the relay 209 is operated. The relay 209 pertains to all the lines in the A group and is operated whenever one of these lines initiates a call. for the purpose of starting the allotted A finder, as will presently he explained. Similarly, the relay 20S applies to the 100 lines of the B group and serves for a like purpose. As was mentioned above, whenever a line is calling the register relays prevent another line either in the same group or in the other group from el'l'ectively initiating a call until :a set of brushes has been tripped serving the first calling line. Should, however, two lines which appear in the same level one in the first half and the other in the second half, simultaneously initiate calls, the tendency would he to start two line finder switches in operation, one in the A group and the other in the B group, inasmuch as the same pair of register relays apply to both lines. This is prevented by making the circuit of relay .209 on the one hand and the circuit 01" relay 208 on the other hand dependent respectively upon the other relay.

lVlien relay .209 is energized it also closes :a circuit from ground through the righthand contact of relay 212, conductor 257,

contact of 0 counting relay 258, winding of stepping relay 218, right contact of relay 209, outer left back contact of relay 207, right contact of relay 223, lower right contact 235 of allotter sequence switch 201, closed in position 1, the lower right contact 108 (1), through the two windings in series of relay 101, lower left contact 116 (1), resistance 117 to battery. It is assumed that position 1 of the allotter sequence switch 201 is the position in which this switch causes the allotment of the finder switch 190, shown in the drawing, and that tie allotter switch is standing in position 1 at the time the call under-discussion is initiated. Relay 101 becomes energized and closes a circuit from ground through its front contact, upper right contact 122 (1), winding of sequence switch magnet 100 to battery. Sequence switch 100 is driven out of position 1 and into position 2. 1n position 2 the relay 101 remains energized in the circuit traced and a circuit is also closed from ground through the front contact of said relay, lower right Contact 107 winding of the trip spindle magnet 102 to battery. The magnet 102 serves to cause the rotation of the brush tripping spindle to select the set of brushes having access to the level of terminals containing those of the calling subscribers line 501.

The stepping relay 218, which was also energized in the fundamental circuit above traced, establishes a circuit from ground through its contact, conductor 260, front cont-act of register relay 212, conductor 261, back contact of the No. 2 counting relay 262, winding of counting relay 263 to battery. Relay 263 operates and completes a circuit from battery through its winding and the winding of relay 262, contact of relay 263, to ground at the inner left contact of relay 219. Relay 262, however, remains shunted and fails to operate as long as the stepping relay 218 is energized. As the tripping spindle passes each brush tripping position, the interrupter springs 10 1 and 105 make engagement with each other, and springs 103 and 10-1 engage each other as long as the tripping spindle is away from its normal position. At each closure .of the springs 10 1 and 105 a circuit is completed from battery through the resistance 117, lower left contact 116 (2), windings of relay'lOl, upper left contact 108 (2), springs 105, 10a and 103 to ground. This circuit holds the relay 101 operated and shunts the stepping relay 218 in the fundamental circuit. At the first shunting of relay 218 it releases its armature and thereby opens the shunt around the winding of the No. 2 counting relay 262. Relay 262 operates and remains energized in series with relay 263.

The tripping spindle continuing to rotate causes the springs 105 and 10st to open,

whereupon the stepping relay 218 is again energized. Relay 218 now extends a circuit from ground through 1ts contact, conductor 260, thence over conductor 261, through the front contact of relay 262, back contact of No. 1 counting relay 26 1, winding of relay 265 to battery. Relay 265 operates and closes a series circuit through its winding and the winding of relay 26 1, contact of relay 265, outer left contactof relay 219 to ground. Relay 2641, however, being shunted by the stepping relay 208 refuses to operate at this time. This procedure continues, an additional pair of counting relays being energized and locked at each brush tripping position passed over by the tripping spindle until the proper set of brushes has been reached at which time the 0 and 0 counting relays 259 and 258 are operated. Relay 258, on operating, opens the fundamental circuit. As soon following the opening of the fundamental circuit at relay 258 as the tripping spindle is accurately positioned for the tripping of the corresponding set of brushes, and springs 1041 and 105 are opened, the relay 101 becomes deenergized. Relay 101 opens, at its front contact, the driving circuit of the trip spindlepower magnet 102 and at its back contact establishes a circuit traceable through the upper right contact 119 (2) and winding of sequence switch magnet 100 to battery. Sequence switch 100 moves out of position 2 and into position 3.

1n position 3 of sequence switch 100 the brush carriage of the finder switch 190 is rotated under the influence of the power magnet 121 to trip the selected set of brushes and to trail them over the terminals of the third level to seek and find the calling line. Since, under the assumption, the calling line 501 occurs in the A group its terminals appear in the first half of the third level of the bank, namely in the first ten sets of terminals. Therefore, the A finder 190, which is the one allotted for use has its set of brushes 148, 149 and 151 tripped and driven over the third level of terminals, and since the calling line appears in the'first half of the level, it will not be necessary for this switch to huntv beyond the tenth terminal. The circuit for the brush earriage power magnet 121 may be traced from battery through the winding of this: magnet, lower left contact 119, back contact of relay 101 to ground. hen the test brush 151 encounters the test terminal 151 of the calling line, it will discover the presence of a battery potential thereon resulting in the closure of a circuit as follows: battery through the winding of the cut-off relay 112 and through the Winding of the message register 175 in parallel and the contact of line relay 205, terminal 151, brush 151, conductor 186, left contact 131 (3 +5) right-hand winding of relay 101, lower left contact 128 (8+17) to ground. Relay 112 is operated in this circuit but the current flowing is insufficient to cause the actuation of the message register magnet175. T16 cut-off relay 112 disconnects the line relay 205 from the calling line and locks in a circuit through its innermost front contact, and thence, as traced, through the winding of relay 101 to ground.

Relay 205, upon deenergizing, immediately opens the circuit which caused the energization of relays 209, 212 and 216, whereby these relays cannot again become energized as a result of this same call.

When the brush 151 first encounters the terminal 151 'a circuit in parallel to the one traced through the right-hand winding of relay 101 is also closed and leads through the lower left contact 109 (8), brush 187, interrupter segment-.118 to ground. As soon asthe brushes 148, 1 19 and 151 are accurately centered upon the terminals of the calling line, brush 187 disengages the segment 118, the shunt is removed from around the winding of relay 101 and this relay becomes energized in the circuit traced. Relay 101, at its back contact, opens the circuit of the power magnet 121 causing the brush carriage to cease its rotation. Relay 101,"at its front contact, completes a circuit leading from upper rightcontact 122 (3), winding of sequence switch magnet 100 to battery. Sequence switch 100 leaves position 8 and moves into position 6. When the sequence switch 100 reaches position 4 the circuit of the cut-off relay 112 is modified so that it now leads by way of terminal 151, brush 151, conductor 188, outer left contact of relay 132, outer left contact 188 (4+11 resistance 18l-to ground.

Furthermore, as sequence switch 100 reaches position 5 a circuit is closed from battery through the lower left winding of repeating coil 150, winding of relay 1 15, upper contact 146 (5-1-11), brush 1 19, over the loop of the calling subscribers line 501 and returning by way of brush 148, contact let? (t-l-ll), upper left-hand winding of repeating coil-150 to ground. Relay 145 becomes energized and a circuit is closed from battery through the winding of relay 158, inner right contact of relay 182, conductor 189, front contact of relay 145, left back contact of relay 1 10, resistance 1414-, upper contact 129 (5+11), inner left back contact of re lay 182, lower right contact 128 (8+16) to ground. Relay 158 becomes operated in this circuit under the control of the supervisory relay 1 15, and at its left-hand contacts extends the talking conductors through to the brushes 159 and 1.60 of the cord selector switch 180. As soon as sequence switch 100 leaves position 5 it opens, at the left contact 131, the circuit of relay 101 and this latter relay becomes deenergized.

Upon the arrival of sequence switch 100 in position 6 a circuit condition is prepared for the operation of the cord selector switch 180 to extend the calling line over an idle cord circuit to the operators position. One of these cord circuits is shown in Fig. 4-. The power magnet 125 for rotating the brushes of the cord selector switch is operated in a circuit from battery through the winding of said magnet, lower right contact 119 (6), back contact of relay 101 to ground. The brushes 159, 160, 161 and 162 are rotated from one set of terminals to another until a set identifying an idle cord circuit is reached. When this occurs a testing circuit is completed from battery through the contacts of key 806 (this key is closed while the operator is at her position), outer left back contacts of relays 811, 810 and 809 in series, inner left back contact of relay 809, winding of said relay, right contacts of key 817 individual to the cord circuit, conductor 851, inner back contact of relay 882, left back contact of relay 881, conductor 18a, brush 162, inner right contact of relay 158, back contact of relay 15-2, right-hand winding of relay 180, lower contact 129 (6), inner left back contact of relay 182, lower right contact 128 .(8-l-16), to ground. Relay 180 operates in the circuit traced and modifies the circuit so that it now leat r through the lefthand winding and contact of said relay, right-hand winding of relay 101, lower lefthand contact 128 (8+17), to ground. The relay 101, however, is shunted by a parallel path through the lower right contact 109 6), brush 191, commutator segment 127, to ground until the brushes of the cord selector switch 180 are accurately centered upon the terminals of the selected cord. Vfhen these brushes are accurately centered the brush 191 disengages the segment 12? removing the shunt and permitting the relay 101 to energize in series with the left-hand winding of relay 180. Relay 101 completes a circuit from ground through its front contact, upper right contact 122 (6), winding of sequence switch 100 to battery. Sequence switch 100 leaves position 6 and moves into position 8.

In position 8 the circuit previously traced through the left-hand winding of relay 180 and the righthand winding of relay 101 is a red so that it new leads through the upper left contact 109 (8-l-11), and thence through the right-hand winding of relay 101 to ground at the lower left contact 128 (SH-1i). This shunt circuit around the winding of relay 180 pern'iits this latter relay to become deenergized so that only the relay 101 remains in series with the relay 809 individual to the cord circuit.

The relays 809, 810 and 811 are three of a plurality of relays, the others not being shown. These relays are individual respectively to the several cord circuits at the opcrators position served by the cord selector switch 180. They are arranged in serial relation with one another in such fashion that the testing circuit whenclosed through one of them, upon the selection of the corresponding cord, causes the energization of such relay whereby the remaining relays cannot be operated and consequently the corresponding cord circuits cannot be selected by the switch 130 or an equivalent switch. At the time the testing circuit is closed through the winding of relay 309, individual to the cord circuit shown in the figure, this relay becomes energized and attracts its armatures. Upon the energization of relay 309 the circuit is modified so that it now leads from battery through the closed contacts of key 308, thence through the outer left back contacts of all other relays in the series, such as relays 311, 310, etc, outer left armature and front contact of relay 309, winding of said relay, right contacts of key 317, conductor 351, and thence as traced through the winding of relay 101 to ground. Relay 309, at its outer back contact, opens the series circuit whereby none of the other relays individual to cord circuits can be operated, thus preventing the selection of another cord circuit until after relay 309 becomes deenergized to restore the closed condition of the series circuit. Relay 309 also completes a circuit from ground through the winding of the common relay 325, lamp 330, inner left front contact of relay 309, cuter left front contact of said relay, through the outer left back contacts of relays 310, 311, etc. in series, to battery through the contacts of key 306; Relay 325 operates and closes a circuit for the pilot lamp 326. Moreover, the lamp 330 is lighted, which lamp is individual to the cord circuit and notifies the operator which one of the cords has been chosen for the extension of a connection. The operator seeing the common pilot lamp 326 burning knows that a call is coming to her position and upon seeing the 'ndividual lamp 330 illuminated is apprised of the particular cord that she is to take for use in extending the waiting call.

The common relay 325, in addition to clos-. ing a circuit for the pilot lamp 320, also establishes a circuit from ground through its left contact through the resistance 3&3, thence to the right-hand armatures of all relays 311, 310, 309, etc, individual to the group of cord circuits selectable by the cord selector switch 330. The back contacts of these armatures are connected to the terminals of the operators cord finding switch 300. The back contact at the right-hand armature of relay 300 is shown as connected by way of conductor 352 with'the terminal 353 in the cord finding switch 360. In a similar manner the back contact of relay 310 would be connected to the corresponding terminal 353 of the next set of terminals, the back contact at, the right-hand armature of relay 311 connected to the corresponding terminal of a third. set in the switch 360, and so on. Immediately that the relay 325 is operated, assuming that the brushes of the switch 360 are standing on the set of terminals representing some cord circuit other than the one shown. in the figure, a circuit is closed from ground through the left contact of relay 325, resistance 3 13, right armature and back contact of relay 311, for example, thence through the contact in the switch 360 corresponding to relay 311, thence over the cooperating brush 35%, inner left back con tact of relay 302, windingof relay 303 to battery. Relay 303 operates and closes a circuit from battery through its front contact through the contact and winding of the stepping magnet 305 to ground. Stepping magnet 305 interrupts its own circuit and advances the brushes of the cord finder switch to the next set of terminals. If this next set of terminals represents a cord circuit other than the one in which the incoming call appears, then the relay 303 remains energized over a circuit through brush 35 1 and a grounded terminal 353, and the stepping magnet 305 advances the brushes another step forward. This continues until the brushes of the switch 360 are advanced to the terminals representing the cord circuit shown in the dmwing, at which time no ground potential will occur on the terminal 353 due to the fact that the right contact of relay 309 is opened. Hence, the relay 303 becomes deenergized and opens the circuit of the stepping magnet 305 permitting the switch 360 to discontinue its forward move ment.

The relay 303, on releasing its armature, closes a circuit from battery through its back contact, contact of relay 313, winding of relay 301, outer back contact of relay 302, to ground at the left contact of relay 325. Relay 301 isoperated 'in this circuit and closes the talking conductors 181 and 182 through to the operators talking set indicated diagrammatically by the character 3 10. The operator now, converses with the calling subscriber and ascertains the nature of his wants. Upon learning the connection desired she seizes the plug 334: of the cord circuit and inserts it in the proper ack'350. lrevious to completing the circuit over the jack 350, the operator may communicate with a distant operator for the purpose of requesting the assignment of a trunk prorided the system is one where this class of connections is involved. An order wire 3 11 of the well-known type is shown by means of which the operator may communicate with the distant operator.

It will be noted that while the operator is talking with the calling subscriber current is supplied through the right-hand Winding of the repeating coil 150 through the winding of the supervisory relay 152. .In case this relay energizes it opens the original oirguit for holding the relay 101 energized in series with the individual relay 309. However, a substitute circuit is provided to meet'this contingency and may be traced by way of onductor 18 1, in the manner previously described, then over brush 162, inner right contact of relay 158, conductor 192, right contact 131 (8), right-hand winding of relay 101, lower left contact 128 (3-I-17) to ground. This circuit being independent of the contact of relay 152 insures that relay 101 remains energized while the operator is communicating with the calling subscriber.

Upon'inserting the plug 33 1 in the jack 350, a circuit is closed from battery through the winding of relay 332, sleeve of plug 334:, sleeve of jack 350 to ground. As soon as relay 332 is operated it opens the circuit of relay 101 and relay 309. Relay 309 restores and reestablishes the series circuit including the other individual relays whereby one of the other cord circuits in this group may be selected by a switch similar to the cord selector switch 180. Relay 309 opens the circuit of the common relay 325 which becomes deenergized and the individual lamp 330 is darkened. A new circuit is closed for the relay 101 as follows: battery, through the winding of relay 331, inner front contact of relay 332, left back contact of relay 331, conductor 184, thence by way of brush 162, inner right contact of relay 158, back contact of relay 152, upper left contact 109 (8-1-11), right-hand winding of relay 101, lower left contact 128 (23-1-17) to ground. Relay 331 operates in this circuit but its re sistance is so high that the relay 101 becomes deenergized. A circuit in parallel with this one also leads through the make-beforebreak contact 114 and the winding of relay 113 to ground. Relay 113, however, being shunted does not operate. The left back contact of relay 331 is so designed that it maintains engagement with the armature until after said armature has made engagement with its front contact. Therefore, relay 331, upon energizing, completes a circuit from battery through its winding and left front contact, thence over conductor 184 as traced, to ground whereby the relay 331 is maintained energized independently of the relay 332.

Relay 332 also completes a circuit from ground through the contact 324 of the common sequence switch 300 which is closed in either positions 1, 3 or 5, provided the operator is at her position, conductor 355, left front contact of relay 332, lamp 328, conductor 183, left contact 136 (8-1-11), inner right contact of relay 132, winding of relay 158 to battery. This circuit through the lamp 328, although closed as soon as the operator plugs in, remains shunted by means of the circuit previously traced through the winding of relay 158, and thence to ground at the contact 128 until the sequence switch 100 advances beyond position 11. Consequently, the lamp 328, which is the calling subscribers supervisory lamp, remains dark.

The relay 331, upon operating, closes a circuit for the lamp 329 which illuminates and remains illuminated until the called subscribed answers. Relay 101, which becomes deenergized when included in series with the high resistance relay 331, completes a circuit from ground through its back contact, upper right contact 119 (8), winding of sequence switch magnet 100 to battery driving said sequence switch out of position 8 and into position 9. In positions 9 and 10 a circuit is closed from battery through the winding of sequence switch magnet 100, lower right contact 177, key 193 to ground. Sequence switch 100 thereupon moves out of position 9 through position 10 and into position 11, which is the talking position.

After the connection has been extended to the called line and ringing current applied in the usual manner, the called subscriber answers by removing his receiver from the switchhook. As soon as the called subscriber responds a circuit is closed from battery through the lower right winding of repeating coil 150, winding of supervisory relay 152, upper contact 153 (10-1-11), inner left front contact of relay 158, brush 160, conductor 182, ring of plug 334:, thence over the loop of the outgoing line through the subscribers substation or through equipment at an operators position, dependent upon the manner in which the connection is completed beyond, and returning over the tip of the plug 334, conductor 181, brush 159, outer left contact of relay 158, left-hand contact 156 (10-1-11), upper right-hand winding of repeating coil 150 to ground. Relay 152 operates and opens the circuit previously traced through the winding of relay 331, and thence through the right-hand winding of relay 101 to ground. There remains, however, the branch circuit including the winding of relay 331 and the winding of relay 113. The relay 113 does not receive sufficient current in series with the windingof relay 331 to operate even when the shunt is removed. Moreover the resistance of relay 113 is also sufficiently high t permit the deenergization of relay 331. Relay 331 becomes deenergized and opens the circuit of the called supervisory lamp 329 notifying the operator that the called subscriber has responded.

\Vhen conversation has been completed the calling and called subscribers replace their receivers on the switchhooks and the supervisory relays 1 15 and 152 become deenergized. The retraction of relay 145 opens one of the parallel circuits including the re lay 158 which has already been traced. Relay 140 now operates from battery through the winding of relay 1438, right inner contact of relay 132, conductor 189, left back contact of relay 115, normal contacts of relay 1&0 and right hand winding thereof, upper right contact 128 (9-1-11), to ground. Relay 1 10 also locks to the same ground through its right armature and front contact. Interrupted ground is connected to the left hand winding, left armature and front contact of relay 1 10 for purposes hereafter described. The release of relay 1 .5 leaves relay 158 included remaining in the remaining circuit which, as above explained, leads over the conductor 183 through the supervisory lamp 328, and thence to ground at sequence switch contact 32 1. The resistance of the right winding of relay 140 being large the shunt has thus been removed from lamp 328 and this lamp becomes illuminated, notifying the operator that the calling subscriber has replaced his receiver on the switchhook. The calling subscriber may regain the attention of the operator by operating the switchhook, which causes the resoperation of relay 145 and connects interrupted ground through the left hand winding of relay 140 and left front contact of relay 1 15, thence to conductor 183 to cause lamp 328 to flash as a recall signal to the operator. The relay 152, in retracting its armature, reestablishes the circuit including the winding of relay 331 and the right-hand winding of relay 101 in shunt of the high resistance winding of relay 113. The decrease in resistance in series with re lay 331 permits the flow of sutiicient current to cause the operation of this latter relay, which, in turn, causes the illumination of lamp 329, apprising the operator that the called subscriber has also retired from the connection. On seeing both lamps glowing the operator withdraws the plug 334; from the jack 350.

The removal of the plug from the jack first results in the deenergization of the sleeve relay 332. The deenergization of relay 332 severs the circuit of the lamp 328 and this lamp becomes extinguished. The opening of the circuit of lamp 328 at the same time causes the deenergization of relay 158. The relay 158. is at this time included in series with the right-hand winding of relay 140 but the resistance of relay 1 10 is too great to permit relay 158 to retain its armatures. Relay 158, upon deenergizing, closes a circuit from ground through its outer right back contact, upper right contact 177 (11), winding of sequence switch magnet 100 to battery, driving said sequence switch out of position 11 and into position 12. In position 12 of the sequence switch a circuit is closed from battery through the winding of relay 158, inne'r'right contact of relay 132, right contact 136 (12+16), resistance 137, interrupter 138 to ground. As soon as the interrupter 138 closes relay 158 operates and completes a circuit from ground through its outer right front contact, upper left contact 177 "(12+16), winding of sequence switch magnet 100 to battery. Sequence switch 100 moves out of position 12 and into position 13. As soon as the interrupter 138 again closes after sequence switch 100 arrives in position 13, the circuit of relay 158 is reestablished and the sequence switch 100 is driven into posit-ion 14.

During the interval that the sequence switch 100 is passing from position 12 into position 1 1, as determined by the interrupter 138,.the operation of the calling subscribers message register 175 occurs in case the call was such as to require registration. The relay 113 will not have been deenergized due to the reasons explained. While the sequence switch 100 is moving from position 11 to position 13 a circuit is established from the source of metering current 174-, left back contact of'relay 113, lower left contact 133 (11 }13 left back contact of relay 132, conductor 188, brush 151, terminal 151, inner left contact of relay 112, thence through the winding of the message register magnet 175 to the opposite pole of battery and ground. The accumulative effect of the two batteries is to operate the message register 175 making a charge against the calling line 501. 7

As soon after the sequence switch 100 reaches position 1 1 as the interrupter 138 closes, relay 158 becomes energized and tablishes the above traced circuit for driving sequence switch 100 out of position 14 through positions 15 and 16 and into position 17. In this latter position the brush carriage of the line finder switch 190 is returned to its normal position by means of a circuit from battery through the winding of the power magnet 121, lower left contact 1.19 (17) back contact of relay 101 to ground. lVhen the brush carriage is fully restored acircuit is established from ground through the lower left contact 128 (3+17), righthand winding of relay 101, lower left contact 109 (17), brush 187, home contact 17!, lower right contact 116 (17) to ba tery. Re-' lay 101 operates, opens the circuit of the power magnet 121 and closes, a circuit as follows: ground, through the front contact of said relay, upper right contact 122 (14+ 17), winding of sequence switch magnet 100 to battery. Sequence switch 100 moves out of position 17 and into position 18. Here a circuit is established from battery through the winding of the trip spindle power magnet 102, lower right contact 107 (18), upper right c0ntact 107 (18+1), closed contacts 10tand 103 toground, lhe trip'spindleis rotated toits 'norma'l'position'at which time the contact 103 enters a deep notch and breaks engagement With the contact 104:. This opens the circuit of the power magnet 102 "and the trip spindle ceases to rotate. lVhile the trip spindle was being restored a circuit was maintained for relay 101 as follows: grounchthrough the contacts 103 and 1041, upper right contact '108 (18), righthand winding of relay 101, left-hand winding ofs'jaid relay, lower left contact116 (18),

resistance 117 to battery. A's soon'as the trip spindle is'restored and contacts 103 and 1041 are opened relay 101 becomes I deenergized "and completes a circuit as follows: ground, through the back contact of relay 1.01, upper right contact ofrelay 119 (18), winding otsequence switch magnet 100 to battery. Sequence switch l00'thereupon restores to its nolanal' position, position '1.

Consider now that'the callbeing extended is one which should notbe accompanied by i an operation of the subscribers message register 17 5. To prevent the actuation of the call meterthe operator operates her key 336 slightly "prior to withdrawing theplug 334; from the jack 350. At this time the sequence switch 100 isin the talking position, position 11. The operation of key 336 completes a circuit from ground through the winding of common relay 335, right contacts 01 key 336, conductor 182, brush 160, inner left contact of relay 158, upper contact 153 (10+ 11), winding of relay 152, lower right-hand winding of repeating coil 150 to battery. Relay 152 operates and removes the shunt from around the Winding or" relay 113, whereby this relay is included directly in series with the windingof relay 331. However, as previouslyexplained, the resistance of relay 331 is too great to permit the operation oi relay 113. In addition to the first circuit a further circuit is closedfby the operation of the opera'tors key 336 and may be traced as, follows: battery, through the resistance 338, contact of relay 337, intermediate contacts of key 336, inner, front con-.

tact of relay 332, left back contact of relay 331, conductor 184;, and thence through the winding of relay 113. Relay 337 also has its circuit closed at the same time but this relay, being slow to operate, does not attract its armature until after the circuit through its back contact has had time to'perform its required function. Theparallel'circuits thus formed through the winding of relay 113 permit suflicient current tofiow for causing the energizationthereof. Relay 113, on operating, immediately locks in a circuit from ground'through its winding and right front cont-act, upperright contact 116 (8+16), resistance 117 to battery.

Later, when restoration is taking place and the sequence switch 100 moves from positions ll 'and 13 in a manner fully explained hereinbefore, the circuit for the operation of the meter 175 is maintained opened atthe left back contact of relay 113. Hence, the'release of the switches takes place without any effect upon the subscribers meter and the call is not charged against his line. I

Another condition to be assumed is one where the nature of the connection being extended is such that it is desirable to enter a double charge against the calling subscriber. In order to accomplish this the operator depresses the key 336 somewhat in advance-"to inserting the plug in the jack. At thistime it will be recalled the sequence switch "100 is standing in position 8. The operation of the key 336, under these circumstances, causes the closure of the circuit preyiously traced through the winding of relay 335 and the winding of he supervisory relay 152. Relay 152 in operating prepares a circuit from battery through the left hand winding or relay 115, rig it coutact'1 12 (8), front contact of relay 152, upper left contact 109 (8+11), right-hand winding'of relay 101, lower left contact 123 (3+17) to'ground. Relay 115 operates and locks in a circuit from ground through its right frontcontact and right-hand armature, upper right contact 116 (8+16), resistance 117 to battery.

After the conversation has been completed and the operator initiates release of the mechanism, the sequence switch 100, on passing from position 11% to position 13 closesthe regular circuit for causingt-he operation of the message register 175, which was previously traced. Considering this circuit again it may be followed from the source of metering battery 17st, left back contact of relay 113, lower left contact 133 (11%/ +13 the outer left contact of relay 132, conductor 188, brush 151, terminal 151, and thence through the winding of the message register 175 to battery. The closure of this circuit causes the operation or" register 175. Shortly thereafter the sequence switch 100 passes from position 15 to position 10. lVhile moving through these positions the metering circuit is closed a second time as follows: battery 17%, left back contact of relay 113, left contact o't relay 115, lower right-contact 133 (15 +10), and thence over the circuit previously traced through the windii'i'g of the message register magnet 17 5. i

It will now be explained how the line finder switches of the A and B groups are allotted for use. It will be recalled that the sequence switch 100 of the switch unit shown in Fig. 1 moved out of position 2 and into position 3 following the brush selection-operation of the finder switch 190. At this time a new finder switch of the A group should be allotted for use in connection with subsequent calls and this is done in the manner now about to be described. iVith the sequence switch 100 in position 3 a circuit is closed from ground through the contact 164 (8-1-18), conductor 266, the lower right contact (1) of the allotter switch 201, right contact of relay 207, and thence in parallel through the windings of the magnet of switch 201 and relay 223 to battery. The alletter 201 moves out of position 1 and into position 2 where it makes a test of the condition of the next switching unit of the A. group. If this unit is busy a contact similar to the contact 16 1 will be in some position from 3 to 18 and hence a circuit identical withthe one just traced is closedfor advancing the allotter 201 out of position 2 and into position 3. This testing operation continues until the allotter 201 reaches some position coresponding to an idle finder switch, at which time it comes to rest thereby allotting that finder switch for use. The relay 228, which operates in parallel'with the allotter 201, serves to hold open the circuit of relay 209, thereby preventing an incoming call from completing the fundamental circuit until the allotment is completed.

The allotter 200, which acts to allot the finder switches of the B group, operates in precisely the same manner and need not be further described.

Initiation of a call in the B group of Zines when one of the B finder switches is e'cZZe.Should, for example, the subscriber of line 508, which belongs in the B group of 100, initiate a call at a time when some one of the B finder switches is idle, the allotted B switch is set in operation to select the calling line in a manner analogous to that explained in connection with the previous call.

There is shown at the left of Fig. 2 a plurality of line relays, and the relation of these with respect to the A and B groups and also with respect to the levels of the finder switch bank will now be considered. The relays 208 and 203 in the vertical row at the right are those of two lines of the A. group which occur in the first level of the finder switches. The two relays below the horizontal line CD in this vertical row are.

the corresponding line relays of two lines in the B group of 100, which likewise occur in the first level of the switches. The relays 20 i and 20 1 in the next vertical row are the relays of two lines of the A group which occur in the second level of the switches, while the two relays immediately below are those corresponding to two lines in the B set or group and appearing'in the second level of the switches. Similarly, the relays 205 and 205 are the relays belonging to two lines in the A group which appear in the third level of the finder switches.

These, for example, may be the relays of lines 500. and 501 diagrammatically illus-. trcte'd' in Fig. 5. The relays below the broken line CD in the same vertical row are those belonging to two corresponding lines in the B group appearing in the third level of the switches, such as. for example, the lines 508 and 509.

When, therefore, the subscriber of line 508 initiates a call he causes the energization of the line relay 267. Relay 267, in addition to placing a selectable potential on the test terminals in the bank of A and B finder switches, completes a circuit from battery through the malre-before-break contacts of relays 214i, 215, 216, etc., thence through the winding of relay 216, as previously traced, winding of relay 212, conductor 252, key 253, left contact of relay 267, key 268, left contact of relay 222, winding of relay 208, left back contact of relay 209 to ground. Relay 216 operates and prepares a circuit for itself over its front contact and at the same time closes a circuit for the relays 210 and 221. Relay 208 operates and opens the operating circuit of relay 209 to prevent the actuation of this relay in case a subscriber in the A group initiates a call. Relay 208 also closes the fundamental circuit as follows: ground, through the right contact of relay 212, conductor 257, contact of relay 258, winding of stepping relay 218, right con tact of relay 208, outer left back contact of relay 206, right contact of relay 222, lower right contact 269 (1), conductor 270, thence to a contact similar to contact 108 of the allotted finder switch of the B group, and through the winding of a relay similar to relay 101. The allotted B finder switch is started inoperation, the proper set of brushes is selected and tripped, and the switch is advanced in its hunting movement to select the terminals of the calling subscribers line This procedure all 108 in the third level. takes place in the same manner as that explained in connection with the previous call.

When the operated B finder switch has completed its brush tripping operation and its'sequence switch 100 moves into position 3, the allotter switch 200 is advanced, and a new unit is allotted for operation to handle subsequent calls occurring in the B group; Moreover, the relays 208, 212 and 216 are decnergized when the line is found as a re sult of the operation of the cut-off relay and these relays, upon restoring, place the coinreon apparatus in'condition for the receipt ofsubsequent connections either in the same or other groups of lines.

Initiation of a call on at line in the A group when all'of the finders 0f the A group are busy.Shouldthe subscriber of line 501 of the A. group originate a call at a time when all finders of the A group, which normally serve these lines as first choice, are busy,

then a finder in the B group, if one be idle, is taken for use to serve the calling line. Assume that the subscriben501'iiiitiates'a call causing the energizationof line relay 205, of relays 216, 212 and also the ei ergization of relay 209. Since all of the finders of the A group are busy the contacts 163, 163, 163 etc. of the sequence switches, ii didua sp e el t t 'fiedsrs e i some position between 3 and 13. Consequently, a series circuit closed through all of these contacts from ground by way of conductor 271 the winding of relay to battery. The relay 20,7 operates and remains energized as 1011s s he Swee ners. busy condition of all switches ofthe A group prevails. Relay 207 heingnergized the funda mental circuit is closed as follows when the relay 209 operates in response to the initiation of a call under the conditions assnn ed: ground, throngh the riglit conta ct of relay 212, conductor 257, contact of relay 253, winding of relay 218,right contact of relay 209, outer left front contact of relay 207, right contactof relay 222, lower right contact 269 (1) conductor 270, and thence through the winding of a relay 20 1 of the allotted idle finder, switch. It will be seen that if all of the A finders are busy when a call occurs in the A group, the fundamental circuit instead of extending to an finder is directed as just traced over the front contact of relay 207, and thence to one of the B finder switches. The relay 207 which is initially energized over tie series circuit including contacts 163, 163 and 163", is not permitted to deenergize when one of the A finder switches becomes idle at a time when the fundamental circuit is being extended through to one of the B switches. This safe guard is provided by a circuit which leads from battery through the winding of relay 207, inner left contact of said. relay, left front contact of relay 209 to ground.

Thus, it is seen-how the fundamental controlling circuit, which controls the brush selecting operation of thefinder switches in accordance with the registration set up on the register relays as a result of the initiation of a call in either the A or B group of lines, is normally extended to the allotted tinder switch of the group which normally serves as first choice the calling line. However, if all of these switches are busy then the fundamental circuit is extended to the allotted finder switch of the other group normally serving the calling line as second choice, provided, of course, there is at the time such an idle switch in the second choice 7 group of switches.

lVhen the operator leaves, her position she opens the key 306 thus permitting relay 307 to. release. Relay 307 closes a circuit for driving sequence switch 300 into either position 2, 4 or 6, opening contact 32 4 The opening of contact 3241 opens an obvious circiiit' which maintains relay 22 5 energized as long asthe operator is at her position. The release of relay 225' closes acircuit for driving sequence switch 220 into one of its even positions. The sequence switch 220 in its even positions places a ground through contacts 227, 228, 229, 23l,'etc., on the contacts of the allotters200 and 201 with respect to all positions in which allotmentis made of finder units 'l aving access to the said operators position. Hence when an operatoris away from her position the allotters will not allot a switch having access tocor ds at such position.

hat is claimed is:

1. Ina telephone system, aplurality of lines divided ii to a plurality of groups, automatic switches arranged in a plurality of groups, each group of switches serving a different group of lines asfirst choice, means allowing each group of switches to serve other lines as second choice, means for operating a; switch in any of said groups to select and extend one of said lines, and

means var'ably operable in accordance with the operation of said'switch for coiiitrolling said switch directively.

2. Ina telephone system, a plurality of lines divided into a plurality of groups, automatic switches arranged in a; plurality of groups, each group of switches serving a different group of lines as first choice, means for allowing each group of switches to serve other lines as second choice, means responsive to a call on one of said lines for operating any one of said switches to select and extend such lines, and means variably operable in accordance with the movement of said switch for controlling said switch directively.

3. In a telephone system, a plurality of lines divided into a plurality of groups, au toniatic switches each having a terminal bank, said lines appearing in the terminals of said switches and divided into a plurality of sub-groups, said switches arranged in a plurality of groups, each group of switches serving a different group. of lines as first choice, means for allowing each group of switches to serve other lines as second choice means for directively operating a switch in any group to a variable extent in accordance with the sub-group of lines to be sc lected, and means for controlling the fur ther operation of said switch to select one Of said lines. 7

4 In a telephone system, a plurality of lines divided into a plurality of groups, automatic switches each having a terminal bank, said line's appearing in the terminals of said switches and divided into a plurality of levels, brushes for each level of lines at each switch, said switches arranged in a plurality of groups, each group of switches serving a ditlcrcnt group of lines as first choice, meanstor allowing each group of switches to serve other lines as second choice, means for directively moving a switch in any group to select the brushes having access to a given level of lines, said directive movement varying in accordance with the brushes to be selected, and means'for con trolling the operation of said brushes to select one of said lines.

5. In a telephone system, a plurality of lines divided into a plurality of groups, automatic switches arranged in a plurality of groups each group of switches serving a different group of lines as first choice, means for allowing each group of switches to serve other lines as second choice, means comprising a counting device for directively operating a switch in any of said groups to select a portion of said lines, and means for controlling said switch in a hunting movement to select and extend a particular one of said lines.

6. In a telephone system, a plurality of lines divided into two groups, a plurality of automatic switches arranged into two groups, each group of switches serving respectively one group of lines as first choice and the other group of lines as second choice, means comprising a counting device for operating a switch in either of said groups to select and extend one of said lines, and means for controlling the operation of said switch directively.

7. In a telephone system, a plurality of lines divided into a plurality of groups, automatic switches arranged in a plurality of groups each group of switches serving a different group of lines as first choice, means for allowing each group of switches to serve other lines as second choice, a counting device common to said switches, means for operating a switch in any group, the operation of said switch causing said device to function to determine one extent of movement of said switch, and means for determining another extent of movement of said switch independently of said counting device.

8. In a telephone system, a plurality of lines arranged in a plurality of groups, automatic switches arranged in a plurality of groups, each group of switches serving a different group of lines as first choice, means for allowing each group of switches to serve other lines as second choice, means for establishing a registration of the identity of: any one of said lines, a counting device common to said switches, means under control of said counting device for operating a switch in any group to select a portion of said lines, and means for operating said switch independently of said device to select a particular line in said selected portion of lines.

9. In a telephone system, a plurality of lines arranged in a plurality of groups, automatic switches arranged in a plurality of groups, each group of switches serving a different group of lines as first choice, means for allowing each group of switches to serve other lines as second choice, means responsive to the initiation of a. call on one of said lines for establishing a registration of the identity of said line, a counting device common to said switchespositioned in accord ance with the established registration, means under control of said device for operating a switch. in any group to select a portion of said lines, and means for operating said switch independently of said device to select a particular line in said selected portion of lines.

10. In a telephone system, a plurality of subscribers lines divided into two groups, automatic switches arranged in two difierent groups, each group ot-switches arranged to serve one of said groups of lines respectively as first choice, and the other group of lines as second choice, registers for taking a. registration of the identity of a calling subscribers line, a variably operable counting device, means for operating a switch to select and extend the calling line, and means under control of saidregistration and said counting device for determining the extent of movement of said switch. 7

11. In a telephone system, subscribers lines arranged in two groups a plurality of automatic switches arranged in two groups, each group of switches serving respectively one of said groups of lines as first choice and the other group of lines as second choice, registers for taking a registration of the identity of a calling subscribers line, means for operating a switch to select and extend the calling line, a. variably operable set of counting relays for determining the extent of operation of said switch, and means dependent on the setting said registers for determining the operation of said counting relays.

12. In a telephone system, a plurality of lines divided into a plurality of groups,

automatic switches arranged in a plurality of groups, each group of switches serving a difierent group or lines as first choice and serving another group of lines as second choice, line designation registering means, a variably operable counting device set in accordance with said registering means, means for operating normally a switch in the group serving a given line as first choice,

the operation of said switch causing said counting device to determine the extent of movement of said switch, means for operating a switch in another group when all switches serving such line as first choice are busy, and means for determining the extent of movement of sa id s-witches' independently of said counting device;

13. In a telephone system, a plurality of lines divided into groups, automatic switches arranged in a plurality of groups,- ea'cli group of switches servings dillerent group of lines as first choice, and serving another group of lines as second choice, means to r operat in g 1101'- ina-ll'y a switclr in the groupserving agiven line as first choice to select and extend such line,- means for operating a. switch in another groupwhen all switches serving such line as. first choice are busy, a register mechanism for taking -a registration 01 said lines, sets of counting. relays positioned in accordance with an establishec'l registration and means for controlling the operation of any of said" switches in: accordance with the operation of the counting relays.

lfl. In a telephone system,- aplurality of lines divided into two groiips, automatic switches arranged in two groups, each group of switches seiwiirg respectively one of said groups of lines asfirst choice-and the other group of lines as second choice, means for al'lotting an idle switchin either group for use, a variably operable counting-device for said switches, means for se'ttfin' said device in accordance: with a line designation, means for operating one" of said su' 'itehes, sa 'id switch While operating cooperating with said counting device to deteri'nin'e the extent of movement of said switch.

15'. In a telephone system, a plurality of lines divided into a plurality of groups, automatic switches arranged in a plurality of groups, each group o1 switches serving a diflierent group of lines as first choice, means for allowing each group of switches to serve other lines as second choice, means for operating a. switch in any group to select a porti'on of said lines, and means for reoperating said switch to seize a particular line in said selected portion.

16. In a telephone system, a plurality of lines divided intoa plurality of groups, autoinatic switches arranged in a plurality or groups, each group of switches servii'ig one group of lines as first choice, and another groupofi lines as second choice, means responsire to the initiation of a call on any line-for establishing a record of the designation thereof, Inea-ns under control of said established record for operating said switch to select the portion of said lines wherein the ca 'ing line is located, and means for reoperating said switch ii'idepei'idently of said record to seize said calling line.

In witness whereof, I hereunto subscribe my nametl'ris 3rd day of February A. 1)., 1922.

GERALD DEAKIN.

Images