US1507966A - Telephone system - Google Patents

Description

sept. 9 1924. 1,507,966

F. S. IRVINE TELEPHONE SYSTEM Filed Sept. l] 1920 5 Sheets-Sheet l -'T f" Il' I Q" sept. 9, 1924. 1,507,966

F. S. IRVINE TELEPHONE SYSTEM Filed Sept. l1 1920 I5 /f71/emor Fran/f 5. /H//ke Affi,

Sept. 9, 1924.

F. S. IRVINE TELEPHONE SYSTEM Filed Sept. ll 192C) A #yf //7 Ve l? for; Fran/r 5. /rV/he.

mallyV served by'such group o yswitches,

Patented Sept. `9, 1924.

y' UNITED ,srArEs PATENT OFFICE;

:FRANK s. IRVINE, OE LONG ISLAND, NEW Imax, AssIGNon fro LWESTERN ELECTRIC4 Y COMPANY, INCORPORATED, OE NEW YORK, N. Y., A OORPORATIONOF NEW YORK. 1

lTELEPHONE "s'Ys'rEm Application l111erlaeptember 11,1920." Serial No. 409,694.5- i

T 0 all whom itrmayooncem: l Y

Beit known that I, -pFRANK S. IRVINE, Va citizen of the United Statesresiding at Long Island, in the countyd'of Suffolk, State of- New York, have invented certainnew and useful Improvements in Telephone Systems, of which the-following is a full, clear,lconcise, and exactdescription. f

This invention relatesto telephone 'sys tems and especially lto systems-'employing containing Vthev calling line may be selected j and utilized to the exclusionof all remaining brush sets. The subdivisionof a group of lines into smaller brushy groups gpermits, as may be seen, the'use of a large capacity switch which requires a comparatively lshort maximum timeinterval a calling line.

In order to decrease as much as possible the operating period of the finder switches it is proposed to urther'divide the brush groups of lines into two subgroups. One of these subgroups 'of each brush group appears as rst choice in half of the total number of 'iinders, assignedvto handle the traffic in the major group of lines, and as second choice in the other half of thefinder of the group serving as first choice they calling subgroup may always vbe used provided sueh group'of finders contains van idle one. Should all finders in a group be busy and a call be originated-in a sub roup, northen a finder in the other 'group which serves the calling'line as second choice, may be started.` s i In case vboth groupsof finden switches'v are simultaneously busy, a call-inlti'ated inl "10, 1923. Reference `to such application-is' either subgroup of lines would, ot course,

in the selection ofi` fail to receive attention. It isI desirable that'a record be kept of the frequency with'v ives'the necessary information bywhich to Vwhich this condition occurs.' Thisy record i Y of yfinders tosuit the traiic requirements'. u

It is, therefore, the object of thisfinven tion to provide,in a system of the' character aboveV set rforth, lmeans for taking a record each'time a call is originated in anyfsubgroup of lines when all 'finders of each of the groups, which normally serve aditl'erent subgroup ofl-lines, are i simultaneously' busy.

SuchLother//features asare contemplated` in the present linvention will become .more apparent fromL the following 'detailedfde-v scription.VVV

Referring"l to the drawing which coni-p` stltutes a part of this disclosure,- Figs'.'f1,` 2'? d and 3, when taken in'order 'romleftfto,

right, illustrate va 'portion of a telephone system embodying; onel adaptation vof .thejy invention. 1

' Fig;y 1 shows two subscribers"telephone lines, one for-each of-'the'two subgroups of a oup of lines served-bythe same set of brushes in the finder switches. This'iigure also shows relays and circuits common to a.

subgroup of lines 'whereby Voriginating kcalls i are extended to' thevcommon starter circuit.

Fig.2 shows a starter circuit commo'nrto`v a pluralityofbrush roups of lines similar tothe one shown-in igl, the function of brushgroup's. Y K .y

- Fig. 3* illustrates'diagrammatically twol groups v of nder-'switches-o'r serving'thel` two subgroups'of lines of all brush groups.

In the "system" disclosed the *division 'of the subscribers lines int'obrush l groups and subgroups,"the method of connecting these lines yto the terminal-banks fof the iinder' switches, the functions of thecominon starter circuit,4v the mannerv inwhich preference 'i' is given to calling linefgroups, thecgrouping ofthe finder switches, the vway in which 4'these' switches, are `allotted' for use, and, in lfact', thev detailed-@operations involved; in vftheiezrte`nsion` of acalling {line' by-fa. finder' switch are substantially identical with those more fully described iithe ate-nt toY F. S. Irvine, No. 1,461,528ygrante {July vA and B subgroups.

, with the terminal bank by meansfof `a common trip rod. The structural arrangement of the finder switches', whereby the proper set of brushes is selected and tripped by the common trip rod, is illustrated and described in the patent to McQuarrie, No. 1,177,044, issued March 28, 1916.

Considering briefly the nature of the systemv in which this invention is incorporated,

it may be assumed that the subscribers linesv are arranged toappear in the lineA finder switches in major groups of 300 lines each, a major group of lines corresponding in number to the capacity of the finder switches. Each major group of lines is divided into ,fifteen smaller groups, each4 of which is served by a different set of brushesin the finder switches Further, a brush. group is subdivided into two groups of ten lines each,

which, for convenience, may be termed the lines of eachbrush group appear in the lower ten sets of terminals before thecorresponding brushesof half of the total number of finder switches serving a major group of lines. That is to say, the total number of finder switches serving a group of 300 lines are divided intotwo groups, `the A and B groups. vAll A subgroups of lines appear as the lower ten lines with respect to the corresponding brushes of all findersin the A group,while theB subgroups of lines appear asthe lower ten lines before the brushes of all finder switches in the B group. In addition the A subgroups of lines appear as the upper ten lines before the corresponding f brushes in the B group o f finders. And similarly the B subgroups of lines appear as the yupper ten lines before the corresponding brushes of the A finder switches. Referring tothe drawing,Fig.1shows one line, 100, inthe A subgroup of a particular brush group and a corresponding line 101 Vin the B subgroup of the same brush group. Above the horizontal broken line in Fig. 3 there are shown diagrammatically four line finder switches ofthe A group which-normally serve as first choice all A subgroups of lines. Below the horizontal broken line there are illustrated four line' finder switches of the B group which likewise serve as first f choice all B subgroups of lines. The line 100, for example, is seen to appear in terminals 300, 301, 302 and 303 in the lower ten sets of terlmnals served by the brushes 304:,

The A subgroup of switch of the A group. Similarly, it will be seen that this line appears in corresponding terminals in the lower ten sets of terminals served by .brushes 319, 320, 321, etc., of all Succeeding finder switches in the A' group. Furthermore, it will be noted that the line 100 is wired to terminals 343, 344, 34:5 and 346 inthe kupper ten sets of terminals before 'the brushes 330 of the first finder switch in the B group. It will be= understood, of course, that the line 100 is also lmultipled to corresponding sets of terminals in the upper ten sets of terminals servedl by brushes, such as 331, 332, 333, etc.,.of the` remaining line finder-switchesy inthe B group.

Line- 101, whichbelongs to the B subgroup of the same brush group, appears as a first choice line in terminals 347, 348, v349 and 350 in the lower set. of ten terminals served by the brushes 330 ofthe first finder switch of the B group, and similarly before the brushes 331,332, 333, etc., of the remaining B finders. Moreover, the line 101 appears in the terminals 308, 309, 310 and 311 in theVv upper ten sets of terminals of the first vline finder switch in the, A group, and similarly in the upper ten sets of-terminalsofthe remaining A e finder switches.v What has beensaid of lines 100 and 101 applies to all otherlinesofwthis brush group and to the lines of both subgroups in theremaining brush groups not illustratedherein. To

summarize briefiy it may be said that all.

lines in the A subgroups are served as first choice by the A grouprof finders, and as second. choice by the B group of finders, and that all lines in the B subgroups are normally served as first choice by the B group of finders and as second choice by the finders of the A group. Y l

The switch 200, shown in. Fig. 2, is an.'k

ordinary step-by-step switch comprising the two brush arms 201 and 202. The pur-V pose of this switch, as is fully explained lin my copending applicationabove referred to, is to change the order in which brush groups of lines may acquire access to the common, starter circuit 1n the event ofv simultaneous calls originatingv in different brush groups. Inasmuch as the present invention isy not particularly concerned with this featurefit has not been considered `necessary to illus-` respectively to the A andB groups ofV finder.y

switches. -Thefunction `of these switches changing `the preferred is to change the order in which the finderA switches are taken foruse. With the preference ,switchv 210 in yits first position las shown `in the drawing, first choice is given f to the first finder switch in the A group. If

this finder switch be idle when a call is originated in an A subgroup, it is set in operationto nd the calling line. If the first finder be busy, however, its relay 322 will be energized and the starter circuit is extended to the next finder in order shown in the A group, etc. At the initiation of each call the switch 210 advances one position whereby the first choice is given to the next switch in order, second choice to the following switch and so on throughout the series. Likewise t-he same holds true with regard to the preference switch 220l and the B gro-up of finder switches.

So long as the group of finders normally serving a particular subgroup of lines contains an idle switch, this switch will be taken for use to extend the calling line.

`When, however, all switches of the group, normally serving as first choice a particular subgroup of lines, are busy and a call originates in such subgroup, then one of the switches of the other group of finders which serve this subgroup of lines assecond choice will be employed. For instance, assume all of the A finder switches were engaged at the time a call is originated in the A subgroup of any particular brush group. In a case of this kind the common starter circuit is so designed that a finder switch in the B group will be started in operation, provided one is idle, to hunt for the calling .line in the A subgroup of lines. `If a call` originates in either of the A or B subgroups at the time that all finder switches of both the A and B groups are simultaneously busy, then, of course, the call must fail due to the fact that no switch is available for serving the same. f l

Considering now the'detailed operation of the system it will be assumed that the subscriber to line 100 in the A subgroup Wishes to obtain a telephone connection and that the first finder switch in the A group, normally serving this line as first choice, is idle. When the receiver is removed from the switchhook a circuit is established from battery through the winding of line relay 102, inner left-hand armature and contact of the cut-off relay 103, conductor 113, over the loop at substation 100, conductor 114, contact and right-hand armature of relay 103 to ground. The line relay 102 becomes energlzed and completes a circuit for -the grou relay 104, common to all lines in the A su group of this particular brush group, to ground at the left-hand armature and contact of relay 102. Relay 104 becomes energized and completes a circuit from ground through its contact and armature, armature and contact of relay 105, left-hand armature and back contact of relay 106, left-hand winding of relay 107, conductor 123, outer left-hand armature and contact of relay 207, outer left-hand armature and contact of relay 208, contact and armature of stepping magnet 209, to battery and ground. Assuming the preference switch 200 to be standing in its first position, thereby vassigning first preference to the brush group shown in F ig. 1, relay 107 locks up over the following circuit: ground, through the Arighthand normal contact of relay. 106, righthand winding and front Contact and inner right-hand armature of` relay 107, conductor 124, terminal 224, brush 201, left-hand armas ture and back contact of relay 203, back con# tact and inner right-hand armature of relay 206, Winding of relay 207, to lbattery-and ground. Relayl 107, therefore, remains en-v ergized and relay 207 attracts its armatures. Relay` 107 completes a circuit from gro-und through its inner left-hand armature and contact, conductor 122, winding of trip magf net 313, Fig. 3, -to battery and ground. The trip magnet 313 rotates the trip spindle 312 which is common to the corresponding set of brushes of all finders in bothV the A and B groups. The trip vspindle in itsvrotated position prepares for the tripping ofthe set of brushes on the particular finder switch that is started invoperation to indl the calling line. f v

Relay 207, which also 107, opens, at its outer left-hand armature and contact, the circuit for. the starter wire 123 to prevent the energization of another relay similar to relays 107 and" 117 in any otherbrush group of lines until the finder` switch serving this particularcall is started inoperation. Relay 207 also closes a circuit from ground through its inner right-hand armature and contact, winding `of. the stepping magnet 209, to battery and ground. The stepping magnet 209, which belongs to the switch 200, energizes preparatoryto advance the brushes 201 and 202 of the pref-- energizes with relay erence switch to their next position termiv nals. Relay 207 further completes a. circuit `from ground through its outer right-hand4 armature and contact, conductor 225,lefthand make-before-br-eak`v contact `of relay 215, brush 212, terminal 218, conductor 226,

through its winding and contact and inner left-hand armature to ground at the contact and armature of relay 314. Relay 318 closes a circuit from ground through its outer. lefthand armature and contact,l contact and right-hand armature of relay 322, conductor f- 227, right-hand make-before-break contact and winding of relay 215,-*V to battery 'and ground. Relay 215 becomes energized and locks up in a circuit frombatte'ry throughits Winding, make-before-break.contact and right-hand armature, Contact and outer right-hand armature of relay 207 to ground.

R-elay 215 completes a circuit from battery through the winding of the stepping magnet 213, brush 211, terminal 228, left-hand armature and make-before-break contact of relay 215, conductor 225, to ground at the contact and outer right-hand arn'rature of relay 207. Stepping magnet 213, which belongs to the switch 210, becomes energized ready to advance the brushes 211 and 212 forward one Ste Relay 318 also closes a circuit at its righthand armature and contact for'the updrive power magnet 316. Power magnet 316 causes the upward movement of the brush shaft 315 whereby brushes 304, 305, 306 and 307 are tripped into operative engage ment with the terminals of the bank. Shortly following the tripping operation the contact 342 is momentarily closed and a circuit established from ground over said contact, conductor 229, back contact and lefthand armature of relay 205, conductor 125. contact and outer left-hand armature of relay 107, winding of relay 106, to battery and ground. Relay 106 attracts its armatures and opens the holding circuit of relays 107 and 207.' Relay 106 locks up in a circuit from battery through its winding and front Contact and left-hand armature, contact and armature of relay 105V to ground at the armature and contact of relay 104. Relay 106, at its right-hand armature and contact, closes a circuit for the right-hand winding of relay 105. This winding is non-inductively woundfso that suflicient -flux is not produced to cause the operation of relay 105. The right-hand Winding of relay 105, however, is capable of maintainingthe armature of said relay attracted once it has been operated by the left-hand winding.

Relay 107, on deenergizing, opens the circuit of trip magnet 313. Relay 207 on releasing its armatures, again closes a con ductor 123 to permit other calling lines to obtain access to the common starter circuit. Relay 207, at its outer right-hand. armature and contact, opens the circuits of relay 215 and stepping magnet 213. Magnet 213 deenergizes and advances brushes 211 and 212 forward one step. Relay 207, at its inner right-hand armature and contact, opens the circuit -of stepping magnet 209 whereby the brushes 201 and 202 are moved yforward to the next set of terminals.

The brush shaft 315 continues its upward movement until brushes 304, 305, 306'and crgized and opens the holding circuit of relay 106. Relay 106 is made slow to release` and, therefore, does not retract its armatures immediately. During the time relay 106 is maintaining its armatures attracted, relay 105 is held operated over its right-hand winding.

Relay 314, which also becomes energized in series with relay '105, opens thecircuit of relay 318, which in turn deenergizes and opens the circuit of the updri've power magnet 316. The finder switch therefore comes to rest in engagement with the terminals of the calling subscribers line. In the manner fully explained in the patent to F. S. Irvine, No. 1,461,528, granted July 10, 1923, the cut-off relay 103 is energized over conductor 115, and line relay 102 releases its armatures to open thecircuit of relay 104. Relay 104 becomes deenergized and a short interval thereafter rela 106 also releases its armatures and opens t e circuit of the right-hand winding of relay 105. Relay 105 thereupon deenergizes. All apparatus associated with the A subgroup of this particular brush group is restored to normal to receive other calls.

lVhen the brush shaft 315 of'the finder switch moves away from its normal position, the off normal contact 326 isclosed and relay 322 becomes energized. This relay indicates the busy condition of the finder switch and serves to extend the starter wire by Way of conductor 226, inner left-hand armature and front contact of relay 322, .to

the inner yleft-hand armature of the relay 323 individual to the next finder switch in the series. After the call has been extended and the conversation completed, the finder switch is released by means of the downdrive power magnet 317 .in thewell-known manner.

Assume next that the subscriber to line 101 in the B subgroup wishes to extend a telephone connection. The removal ofthe receiver from the switchhook completes a circuit for the line relay 108 over the inner lefthand armature and contact of relay 109, conductor 119, through the loop of the substation, conductor 118, to ground at the right-hand armature of relay 109. Relay 108, to ground at right-hand armature of relay 109. Relay 108, in a manner similar to that already described closes a circuit for relay 110. Relay 110 completes a circuit from ground. through its contact and armature, armature and contact of relay 111, left-hand armature and back contact of relay 112, left-hand Winding of relay 117, conductor 123, left-hand armatures and contacts of relays 207 and 208, to battery and ground through the contact and armature of stepping magnet 209. Relay 117 becomes energized and locks up over its righthand Winding through the first position terminal-of brush 202 of the preference switch 200, left-hand armature and back contact of relay 204, back contact and inner right-hand armature of relay 205, winding of relay 208, to battery and ground. Relay 117 closes a circuit from ground through its contact and inner left-hand armature, conductor 122, winding of trip magnet 313, to battery and ground. Relay 208 opens the starter circuit 123 to prevent other calls from reaching the group circuit and also closes a circuit at its inner right-hand armature and contact for the energization of the stepping magnet 209. Relay 208, at its outer right-hand armature and contact, closes a circuit by way of conductor 230, left-hand make-before-break contact of relay 216, brush 222, terminal 223, conductor 231, to the armature of relay 334, and thence, as described, to the winding of a relay corresponding to relay 318. The lirst finder switch of the B group is thereby started in operation to position its brushes 330 on the terminals 347, 348, 349 and 350 of the subscribers line 101 in the B subgroup; As already explained in the call above traced in detail, relay 216 becomes energized, locks up and prepares a circuit for the stepping magnet 214 of the preference switch 220. v

As soon as the brush set 330 has been tripped by the position trip rod 312, relay 112 becomes energized and locks up in the manner explained in connection with relay 106.

When the calling line has been found by the brushes 330, relay 111 becomes energized and `opens the circuit of relay l112. Shortly after this occurs the cut-olf relay 109 is operated and relay 110 becomes deenergized. At the end of the necessary interval the slow to release relay 112 retracts its armatures and opens the circuit of the right-hand winding of relay 111.

When the first finder switch of the B group is taken for use, the relay 334 becomes energized in a circuit including the off normal contact 338 to indicate the busy condition of this switch The deenergization of relay 208, which occurs at the time relay 117 is released, opens the circuit of magnet 209 causing thereby the advance of the switch 200 to the next position. Relay 208, on deenergizing, also opens the circuit of the stepping magnet 214 and the switch 220 moves forward to change the order of preference in which the B finders are taken for use.

Assume now that a call is initiated on a line such as line 100 in the A subgroup at the time all of the A finder switches are busy. Since all of the A finders are already in use, relays 322, 323, 324, 325, etc., individual to these finders respectively are energized. Consequently, the following circuit is established for vthe energization of relay 203; ground, through the outer left-hand armatures and contacts of relays 325, 324, 323 and 322 in series, conductor 232, left-hand winding of relay 203, to battery and ground. When, therefore, relay 107 becomes energized over its left-hand winding in response to the initiation of a call on line 100, the following circuit is established: ground, through the right-hand normal contact of relay 106, right-hand winding and front contact and inner right-hand armature of relay 107, conductor 124, terminal 224, brush201, left-hand armature and front contact of relay 203, winding of relay 205, to battery and ground. Relay 205 becomes energized and closes a cir-l cuit from battery through the winding of relay 208, inner right-hand armature and front contact of relay 205, back contact and outer right-hand armature of relay 204 to ground. Relay 208 attracts its armatures and causes the operation of one of the B finder switches as has already been explained. From this point on the operation of the selected B finder to extend the calling line'100 in the A group progresses in the manner explained in detail in connection with the operation of one of these inders to extend a irst choice line, such as line 101 in the B subgroup. Switch 220 is advanced one position as above described to change the order of preference in which the B finders are to be used.

Assume next that all of the nders of the B group are engaged at the time a call is initiated on a line, such as line 101, in the B subgroup normally served as first choice by the' B finder switches. In View of the fact that all of the B finders are busy, relays 334, 335, 336 and 337 are energized and a series circuit is established over their outer lefthand armatures and contacts, conductor 233, left-hand winding of lrelay 204, to battery and ground. Relay 204 is energized in this circuit. When relay 117 attracts its armatures in response to the initiation of a call on line 101 in the B Subgroup, a circuit is established for holding this relay as follows: ground, through the right-hand normal contact of relay 112, right-hand winding and front contact and inner right-hand armature of relay 117, conductor 126, brush 202, lefthand armature and front contact of relay 204, winding of relay 206, to battery and ground. Relay 206 completes a circuit from battery through the winding of relay 207, inner right-hand armature and front contact of relay 206, lto ground at the back contact and outer right-hand armature of relay 203. It is assumed, of course, that some finder in the A group is idle and that consequently relay 203 is deenergized. Relay 207 operates as already explained to initiate the hunting movement of one of the finders' of the A group to serve the calling line.

It has been seen how the A and B nders are normally taken for use to serve their lirst choice lines when any of the finders are .idle at the time calls originate on such lines, and, furthermore, how either of these groups of finders may be taken to serve their second choice lines whenever all finders in the normally assigned group are simultaneously busy. 'Ihe last condition that may arise is one in which a call is initiated in either the A or B subgroups at a time when all the finders of both the A and B groups .are busy. rlhis means a complete failure of the call to receive attention. In order that a record may be taken of the frequency with which Ithis condition arises, a. register is installed which counts the number of times that calls fail to secure service on this account. Since all of the finders are busy the relays 322, 323, 324, etc. and relays 334, 335, 336. etc. are energized and both relays 203 and 204 are operated as above described. If then relay 107 becomes energized in response to the initiation of a call in the A subgroup, relay 205 is operated as ex lained. Relay 205 docs not succeed in comp eting the circuit hereinbefore traced for relay 208 since this circuit is now opened at the back contact and outer right-hand armature of relay 204. Relay 205, however, does close a circuit from battery through the winding of register 217, outer right-hand armature and contact of relay 205, front contact and outer right-hand armature of relay 204, to ground. The register 217 operates to register one count on i the counting mechanism.

In a similar manner should a call originate in the B subgroup, relay 117 energizes and closes a circuit for relay 206. Similarly, relay 206 fails to complete the energizing circuit of relay 207 in view of the fact that this circuit is already opened at the outer right-hand armature and back contact of relay 203. Relay 206, however, completes a circuit for the register 217, `traceable over the outer right-hand armature and contact of relay 206, to ground at the front contact and outer right-hand armature of relay 203. Register 207 accordingly takes another step to record the initiation of another call which failed to secure service due to all finders being simultaneously busy.

lVhat isclaimed is:

1. In a telephone system, subscribers lines arranged in a plurality of groups, a plurality of groups of automatic switches, each group of switches arranged to normally serve a different one of said groups of lines, a register, and means responsive to the initiation of a call in any of said groups of lines when all the switches of all of said groups of switches are busy for operating said register.

2. In a telephone system, subscribers lines arranged in a plurality of groups, a plurality of groups of line linder switches, each group of switches arranged to normally serve a different one of said groups of lines, a register, means responsive to the linitiation of a call in any of said groups of lines when all the finder switches of all of said groups of switches are busy for operating said register.

3. In a telephone system, subscribers lines arranged in a plurality of groups, a. plurality of groups of automatic switches, each switch arranged to serve all of said groups of lines, each group of switches arranged to serve as first choice a different one of said groups of lines, a register, and means responsive to the initiation of a call in any of said groups of lines when all the switches of all of said groups of switches are busy for operating said register.

4. In a telephone system, subscribers lines arranged in a plurality of groups, a plurality of groups of automatic switches, each switch arranged to serve all of said groups of lines, each group of switches arranged to serve as first choice a different one of' said groups ot' lines, means responsive to a call in any group of lines to operate an automatic switch in the group normally serving such group of lines as first choice, means for operating a switch in another group when` all of the switches normally serving as first choice the group of lines containing the calling line are busy, a register, and means responsive to the initiation of a call in any of said groups of lines .when all the switches of all of said groups of switches are busy for operating said register.

5. In a. telephone system, subscribers lines arranged in a plurality of groups, a plurality of groups of line finder switches, each finder arranged to serve all of said groups of lines, each group of finders arranged to serve as first choice a different one of said groups of lines, means responsive to the initiation of a call in any group for operating a finder switch of the group normally serving as first choice the groupcontainingy the calling line, means for operating a finder switch in another group when all of the finders of the group normally serving as first choice the group of lines containing the calling line are busy, a relay for each group of finder switches, means for operating said relays when all of the finde-r switches of the corresponding groups are busy, a register, and means responsive to the initiation of a call in anyv group of lines when all of said rela-ys are operated for actuating said register.

6. In a telephone system, subscribers lines arranged in two groups, a plurality of finder switches, each switch ,arranged to serve all of said lines, said switches being divided into two groups, each grou serving as first choice a different one of said groups of lines, means responsive to the initiation of a call in either of said groups of lines Jfor operating a finder switch normally serving as first choice that group of lines, means for o erating a finder in the other group when al the finders normally serving as first choice the group of lines containing the calling line are busy, a register, and means responsive tothe initiation of a call in either group of lines when all of the iinders of both groups of finders are busy for operating said register.

7 In a telephone system, telephone lines arranged in a plurality of groups, a plurality of groups of automatic switches, each switch arranged to serve all of said groups of lines, each group of switches arranged to serve as first choice a diii'erent one of said groups of lines and a device for counting all calls initiated in any group of lines at a time when all switches of all groups of switches are busy.

8. In a telephone system, subscribers lin arranged in a plurality of groups, a plurality of groups of automatic switches, each switch arranged to serve all of said groups of lines,each group of switches serving as first choice a different one of said groups of lines, a measuring device, and means responsive to the initiation of a call in any group of lines and dependent on the simultaneous busy condition of all switches in one of said groups of switches for operating said measuring device.

9. In a telephone system, subscribers lines arranged in a plurality of groups, a plurality of groups of automatic switches, each group of switches arranged to serve as first choice a different one of said groups of lines, all switches arranged to serve all lines,

means responsive to a call in any group of lines to operate an automatic switch in the group normally serving such group of lines as first choice, means for operating a switch in another group when all of the switches normally serving the calling group are busy, a register, and means responsive to the initiation of a call in any group of lines and dependent on the simultaneous busy condition of all switches in one of said groups of switches for operating said register.

10. In a telephone system, subscribers lines arranged in a plurality of groups, a plurality of groups of automatic switches, each switch having a plurality of brushes for making connection with said lines, each group of switches arranged to serve normally a different one of said groups of lines, means for selecting the brushes of said switches, a register, and means responsive tothe initiation of a call in any of said groups of lines when all the switches of al1 groupso-f switches are busy for operating said register.

11. A telephone system comprising subscribers lines arranged in groups, automatic finder switches of the panel type for extending said lines, a register, and means whereby a plurality of said switches jointly voperate said re ister.

In witness w erect, I hereunto subscribe my name this 9th day of September, A. D.

FRANK S. IRVINE.

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