US1604550A - Rotary final selector switch - Google Patents

Description

Qct. 26 1926.

' G. DEAKIN ROTARY FINAL SELECTOR SWITCH Filed Sept. 13, 1924 w. uw., M m. m. M j SQ m n u i W m www A 5.a 6 n u h i /IAETw 6 A U @mwm Vxmm wvli am kvm. y NSM *n \Nmvw00oNomf ,0000000000 u RW- J xwwm. Hf. Y Y n@ .Y www MQ Patented Ust. 26, 1926.

Slllr'll' rarer trice.

GEIALD DEAKIN, OF ANTXTERP, BELG'IVI, ASSGNOR TO TESTER/N ELECTRIC COM-V PANY, NCORPR-ATED, OF NEW YORK,

N. Y., A CORPORATION OF NEW YORK.

ROTARY FNAL .SELECTOR SWITCH.

Application lcd September 13, 1924, Serial No.

rllhis invention rela-tes to telephone eX- change systems and particularly to final selector or connector switches adapted to establish connections with a desired line.

In automatic and semi-automatic systems, it is necessary to provide service for both ordinary individual subscribers lines and private branch exchange lines. In accordance with well known practice, in extending l connections to an individual subscribers line, the final selector switch moves directly, in accordance with the designation of the line, on to the contacts of the line and there comes to rest. For calls to a private branch en change, the switch is set in accordance with the designation of the private branch exchange, on the contacts ot' the iirst line in the group ot equivalent private branch eX- cliange lines and remains there it this line 20 is idle. lt, however, it is busy, the switch operates to move its brushes over the lines in the group until an idle line is found, at which time the switch comes to rest. lnV such an operation it all the lines of the group are busy the switch is arranged to bring its brushes to rest on the last line oi the group of trunk lines whether this line is idle orv busy.

ln automatic telephone systems heretofore proposed, the testing arrangement of switches serving both main lines and private branch exchanges, or multigroup lines in the manner indicated, have been complicated and have included either a number of relays with various adjustments or a plurality ot test brushes necessitating' a plurality of test terminals for each line.

lt is the object ot the present invention to provide means for automatically enabling a switch to serve individual lines or private branch exchange lines in any level ot its bank. y

ln accordance with one `teature of 'the present invention, the switch may be posi` tioned on a specilic one ot twenty tern'iinals in any of its bank levels or may be used tor hunting over the remaining terminals of the bank tor an idle private branch exchange line.

ln carrying out this invention, the arm which carries the switch brushes automatically changes the circuitfor controlling the movement oi the brushes irom a selecting? 7321477, and in Great Britain October 5, 1923.

to a hunting movement when the arm reaches a position in which the brushes rest on terminal 20.

These and other 'features of the invention will be set forth in the following description and claims and will be readily understood by reference `to the accompanying drawing where: l

Fig. 1 is a diagrammatic sketch ot the se-` lector switch, terminals and arm, showing cut-over contacts operated by the switch arm;

ln Fig. 1 a single level of a switch embodying the invention has been diagrammatically illustrated as comprising thirty contacts, lthe tirst twentycontacts, 1 to 20, inclusive, being the normal contacts of the switch. The last ten contacts, 21 to 30, represent ten additional contacts added' to the level, these contacts together with the nor` mal last contact 2O ot the level being the terminals oit private branch exchange lines. rllhis switch may be ot Vthe type ldisclosed in the patent to ll. R. McBerty, No. 1,097,868, is-V sued May 26, 1914: comprising Vten bank levels. lhe shaft 31 ot the switch has secured thereto a pluralityof sets of brushes, only one of which is shown at 32, these brushes being movable over the contacts in the sepaw rate levels. The brush shaft also carries an insulated member 33, which is designed to engage the switch 152 and move spring 3st into contact with spring 35 when the brush 32 comes into contact with contact 20. The

Vclosure ot the springsBt and 35 changes the circuits of the final selector switch in. a manner later on described and adapts the switch to act as a hunting switch Jfor selecting an idle contact among the set of contacts 2O to 30 of any level. Y

It will, of course, be obvious that the springs 34 and 35 may be arranged to close in any position of the level so as to cause the brushes to hunt automatically over the remaining contacts. This may be the case where the level is provided with additional contacts in the manner illustrated or simply comprising the usual number of contacts in the level. ln this way all final selector switches may serve for the extension of calls to private branch exchanges resulting in a greatly increased eliciency ot the apparatus usen.

of m

Fig. 2 shows a selector switch circuit incorporating the features of the invention, and

Fig. 3 shows a group of three private branch eichange lines, one of which is the last line, connected to terminals of the switch of Fig. 2.

@alla to ord/nary direct Zin-cs.

lt is thought that the invention will be best understood from a detailed description of the circuits. lhen the fundamental circuit is closed by the usual registering and controlling or sending equipment (not shown) line relay operates in a circuit from battery through the lower left Contact of cam 101, lower lett contact of cam 102, conductor 103 over the fundamental circuit, through the winding of the stepping relay and contacts of relays in the sender, back over conductor 104, lower right contact ot cam 105 to ground. Relay 100 energizes and closes a circuit for operating test relay 106 which may be traced from battery, upper lett contact of cam 107, resistance 149, winding of relay 106, contacts et cam 108, right front contact and armature oit relay 100, upper right contact of cam 111 to ground. Relay 106 energizes and locks to ground through its liront contact and armature. A circuit is also closed when relay 100 energizes tor operating relay 114 from battery through the winding oi2 relay 111i,

through resistance 109, upper contacts of cam 115, lower left contact of cam 116, right trontcontact and armature of relay 100 through the right upper contact of cam 111 toground. Y

)relay 114; upon energizing, clos-esa circuit for moving` sequence switch 117 out et position 1, which may be traced from battery through the winding of sequence switch magnet 117, lower lett contact of cam 119 through the trent contact and armature oi relay 11d to ground. The circuit ot relay 11st is opened when lsequence switch 117 leaves posi-tion 1. in position 2 et sequence switch 117, relay 100 is held operated over the 'fundamental circuit over the lett contact ot cam 127, lett iront Contact ot relay 100 and closes a circuit tor the trip spindle magnet 122 which is closed from battery through the winding of magnet 122, upper right contact oi cam 116, right liront contact and armature oit relay 100, upper right contact ot cam 111 to ground. The trip spindle now rotates, closing the interrupter springs 124:, 125 and 126 once tor each step oi the interrupter, thereby closing` a circuit from ground through the said springs, lower right contact otcam 101, upper left Contact ot cam 127, left 'front contact and armature of relay 100, right contact oi cam 139, lower right contact ot cam 102 over conductor 103 to the sender. The interrupter springs 124,

125 and 126 are normally open when the switch is in the normal position but after the trip Spindle is moved trom its normal position, springs 12-1 and 125 are Closed and remain closed until the trip spindle returns to normal. During the movement oi the trip spindle, spring 126 is moved into contact with spring 125 and as the latter is in engagement with spring 1211-, ground is intermittently connected to the upper spring 126. This ground connection intermittently short circuits the stepping relay in the sender, in the well known manner, one impulse being given for each step taken by the trip spindle. `After the tens register of the sender has been satislied and the controlling relay of the sender is energized to open the fundamental circuit, relay 100 deenergizes and the circuit Jjor the trip spindle magnet 122 is opened whereby the trip spindle is stopped in a position corresponding` to the setting ot the sender register and in position to trip the correct set of brushes on the linal selector. lilith relay 100 deenergized, sequence switch 117 is advanced to position 3 by a circ*- it extending from battery through the winding ot sequence switch magnet 117, left upper contact oit cam 131, right baclr Contact and armature ot relay 100, upper right contact et spring 111 to ground. On leaving position 2, the circuit oi the test relay 106 is opened. In position 3, a circuit is closed tor relay 11-1 which may be traced 'trom battery through the winding oi relay 11-1, lower lett contact of cam 131, right back contact and armature of relay 100, upperl contact ot cam 133, springs 125 and 12e of interruptor 123 to ground.

lWhen the sender circuit is in position for units selection, the Jfundamental circuit is again closed. Relay 100 is operated thereby deenergizing relay 114e and closing a circuit tor sequence switch 117 from battery through the sequence switch magnet 117, lower right contact of camY to ground on the back Contact and armature of relay 11-1. Vaequence switch 117 thereupon moves into position Li in which position relay 100 is loclzed over the fundamental circuit as previously described. rl`he brush carriage magnet 135 is now energized in a circuit from battery through the power magnet 185, upper lett contact of cam 136, right front contact and armature of relay 100 to ground through the upper right contact oit cam 111. rlhe brush carriage magnet 105 thereupon operates to rotate the brush carriage, the selected set ot arushes determined by the setting of the trip spindle magnet, being tripped and thereafter wiping` over the contacts in the bank ot the switch corresponding to such set of brushes. lluring this operation, the interrupter contacts 137 and 138 are closed intermittently, thereby connecting ground through llO the lower right contact of cam 101, left upper contact of cam 127, left front Contact and armature of relay 100, upper right contact of cam 139, lower Vright contact o't cam 102, orer conductor 103. rllhis ground intermittently short circuits the stepping relay in the sender circuit in the well known manner and the selection being completed, the fundamental circuit is opened, relay 100 is deenergized and the circuit for the brush carriage magnet 135 is opened, causing brushes 162, 165 and 145 to come to rest upon contacts 163, 164 and 143, respectively, of the called line. Sequence switch 117 is now energized in a circuit which may be traced lroin battery, winding of sequence switch magnet 117, right upper contact or" cam 131, right back `Contact and armature ot relay 100 to ground through the upper right contact of cani 111. Sequence switch 117 moves :troni position 4 into position 6 by means of ground on master contact 113, after which, the circuit above traced is again closed, moving 'sequence switch 117 from position 6 into position 7. Contact 113 carries the switch into position 3. 1n passing through positions 5 to 7, relay 114 Ais again energized in a. circuit from battery through the winding of relay 114, resistance 109, upper contacts of cam 115, back contact and .armature of relay 142, upper right con tact oit' cam 143, conductor 144 Vto ground in the incoming selector circuit. In positions 7 to 7% ot sequence switch 117, relay 142 is connected across conductors 104 and 103.

This circuit may be traced from conductor 104, lower lett contact o1' cam 105 through the winding of relay 142, lower lett contact of cani 139, lower right contact of cam 102 to conductor 103. Relay 142 is energized from batteryand ground inthe incoming circuit and opens the Acircuit for relay 114, allowing it to deenergize. The deenergization of relay 114 closes a circuit for sequence switch 117, extending from battery, winding of magnet 117, lower right Contact of cam 119 to ground on the back contact and armature ot relay 114, thereby moving the switch into position 9.

In position 6 of sequence switch 117, the test. reay 106 is connected to the test brush 145 and as the called line is assumed to be idle. relay 106 is energized in a circuit from battery through the cut-oil relay 146 and service meter v147 of the called line in parallel, test terminal 143 brush 145, upper right and lower lett contacts oi` cam 107, winding oic relay 106, resistance V133 to ground through the upper lett Contact of cam 111. l/ilhen the sequence switch 117 moves between positions 6 and 7, resistance 149, which may be 7 00 ohms, isintroduced into the circuit ot relay 106, as the lower le'ft contact ot cam 107 is opened. 11s the called line is assumed to be idle, the battery vpotential ont'erininal 148 will be such that :the

which would otherwiseexist in position 7 tor relay 100, from battery through the winding of relay 100, lower contacts of cani 150 to ground on theback contact of relayA 106. Relay 106 also disconnects ground from switch 152, comprising contacts 34 and 35 of Fig. 1, thereby insuring that the switch be used at this time for individual lines only.

Sequence switch magnet 117 is energized in position 9 over a circuit extending 'from battery through the winding of magnet 117, upper left contact ot cani 119, back contact ol relay 142, lower right contact of cam 143 to ground on the front contact and armature ot relay 114. Relay 1.14 was `energized in a circuit from battery through the winding of relay 11.4, lower right and upper left contacts oi' cam 155 over conductor 144 to ground at theinconiing selector.

Sequence switch 117 moves from position 9 into position 11 under control of its master contact 113. 1n position 10, relay 100 is energized in a circuit `trom "battery through the winding ot relay 100, upper lel'tand lower right contacts of cani 143, to ground on the front contact 'and armature of relay 114. Relay 100 upfon energizing,` closes'a locking circuit for itself extending from battery, winding of relay 100, let-tupperV contact of cam 143. back contact and armature of relay 142, lower `left Contact oicam 116, right vfront contact and armature 01: relay 100to ground throughithe upper right contact of cam 111. In position 11 '01"' sequence switch 117' a circuit is also closed from battery through the winding of quence switch `magnet 117, upper left contacts of cam 119, lower left contact of cam 116, right vliront contact and armature of relay 100 to ground through the right upper contact of cani 111. Sequence switch 117 thereupon moves from position 11 into posi tion 12.

In position 12, relay 114 .is connected to interruptor 156 in a circuit extending from battery through the winding of relay 114, resistance 109, lett upper and right lower contacts of cam 115 toground througlifin-V terrupter 156. the circuit is closed at the interruptor and closes a circuit ttor sequence switch 117 L:trom battery through the winding ot switch inagnet 117` lowerleit 'contact ot spring 119 to ground ontlie front Contact and armature of relay 114. This circuit moves sequence switch 117 trom position 12 to position 13 in which position a circuit 'for energizing relay114is again closed `,from battery, wind- 12o Relay 114 energizes when` ing of relay 114, resistance 109, lower contacts of cam 155 to ground through interrupter 157. Sequence switch 117 is now moved from position 13 in a circuit from battery, winding ot sequence switch magnet 117, lower left contact of cam 119 to ground on the front contact and armature o1' relay 114. In positions 12 and 13 of sequence switch 117 a ringing circuit is completed from a source olf ringing current 15S, upper right contact of cam 154, winding of relay 142, upper right contact of cam 127, left front contact and armature of relay 100, upper contacts ot cam 139 to brush 162, contact 163 and thence through the bell magnets at the called subsoribers station, back over contact 164` brush 165 to ground through the upper right and lower left contacts ot cam 159.

This application of ringing` current results in the immediate ringing of the called subscribers bell. relay 142 beine` adjusted so as not to be energized by this ringing-f` current. llVhen sequence switch 117 reaches position 14 under the control ot interrupters 156 and 157, intermittent ringingl current is supplied to the called station from source 160 through the interrupter 161 lower right contact of cam 154 and thence over the circuit previously described.

The ringing current passing through relay 142 is not sutticient to energize it but upon the response of the called subscriber, direct current is superimposed upon the ringing current causing relay 142 to energize whereupon the circuit for relay 100 is opened at the back contact and armature of relay 142. A circuit is now closed from battery through the winding of sequence switch magnet 117, lett upper contact of cam 131, right back contact and armature of relay 100 to ground through the upper right Contact of cam 111. When sequence switch 117 moves into position 15, which is the talking position, the talking circuit is completed Yfrom conductor 103, right upper contact ot cam 102 brush 162. contact 163 through th-e subscribers station Contact 164,

brush 165, upper contacts of cam 159 overl conductor 104.

1t'Vlier the calling subscriber replaces the receiver upon the switch hook, relay 114 which was held energized over conductor 144, is deenergized and a circuit. is closed from battery through the winding of sequence switch magnet 117, lower right contact of cam 119 to ground through the back contact and armature ot relay 114. lThis Vcauses sequence switch 117 to move out of position 15 into position 16 and if the called subscriber has replaced his receiver upon the switchhoolr, relay 114 remains deenergizecl in this position and sequence switch 117 continues to rotate into position 17. Relay 100 is now energized in a circuit from battery through the lwinding thereof, lower Contact of cam 133' to ground through the springs 12o and 124 of interrupter 123. The circuit for the trip spindle magnet 122 is now closed from battery, winding of inagnet 122, upper right Contact ot cam 116, right front contact and armature of relay 100 to ground through the upper right contact ot cam 111. rllhe trip spindle returns to normal in this circuit. lVhen springs 124 and 125 of interrupter 123 are opened, relay 100 is deencrgized and the circuit 'for magnet 122 is opened. The trip spindle then comes to rest. When relay 100 deenergizes, the circuit for sequence switch 117 is closed from battery, magnet winding` thereof, upper lett contact ot cam 131, right back contact and armature of relay 100 to ground through'the upper right contact of cani 111 and sequence switch 117 is moved into position 18. The circuit of the brush carriage magnet 135 is now closed from bat tery through the winding thereof, lower lett contact of cam 136, right back contact and armature of relay 100 to ground through 'he upper right contact of cam 111. The brush carriage is rotated by magnet 135 and is returned to normal when the circuit ot relay 100 is closed from battery, winding ot relay 100, upper right contact of cam 101 to ground on spring 171. Relay 100, upon energizing, opens the circuit before traced for magnet 135 and stops the movement ot the frusli carriage. Sequence switch 117 is returned to normal over a circuit which may be traced from battery, winding of sequence switch magnet 117, le'lt upper contact of spring 119, lower left contact of cam 116 right front contact and armature ot relay 100 to ground through the upper right contact ot cam 111. llihen'the sequence switch reaches normal, relay 100 deenergizes. Relay 106 is at this time deenergized since its locking circuit opened at cam 107 when sequence switch 11 lett posi- V1 tion 16.

@alla 150 ord/nary direct [fi/nes. Line busy.

1t the called line should be busy when tery potential on the test terminal 143 is `insuiiicient to allow test relay 106 to energize. In position 9 ot the sequence switch 117, relays 100 and 142 are energized, the former in a circuit from battery through its winding, lower contacts of cam 150 to ground on the back Contact and armatur of relay 106. Relay 142 is Venergized in a circuit from battery through resistance 153, lower left contact of cam 154, winding ot relay 142, upper left and lower right contacts of cam 150 to ground on the back contact and armature of relay 106. rilhe circuittor n'ioving sequence switch 117 out of position 9, hereinbefore traced, is opened at the back contact and armature of relay 1112 so that the sequence switch remains in position 9. ln this position, relay 100 being energized, a busy tone is applied to the calling` line trom the source et busy tone current 175, lower right contact ot cam 127, lett tront contact and armature of relay 100, upper rightcontact oi cam 139, lower right contact of cam 102 over conductor 103 to the calling subscribei"s line back over conductor 1011, upper lett and lower right contacts ot cam 159, right front contact and armature ot relay 100 to busy potential 132 on the upper lett Contact ot cam 116. This busy tone current produces a tone informing the calling subscriber that the called line is busy.

When the calling subscriber replaces his receiver upon the switchhook, the preceding switches are released and relay 114 is deenergized. A circuit is thereupon closed from battery, winding of sequence switch magnet 117, lower right. contact ot cam 119 to ground on the bach contact and armature oi relay 1141. Sequence switch 117 moves into position 10 and then into positionll under control ot master contact 118, opening the circuit ot relay 100. In position 11 the brush carriage magnet 135 is energized in a circuit extending from battery through magnet 135, lower lett contact ot' cam 136, right back contact and armature ot relay 100 to ground on the upper right Contact of cam 111. The brush carriage thereupon returns to normal position. TWhen contact 171 closes, ground is connected through the right upper contact of cam 101 through the winding of relay 100 to battery, energizing relay 100 and opening the circuit of magnet 135, causing the brush carriage to come to rest. Sequence switch 117 is energized over a circuit from battery through the winding of sequence switch magnet 117, upper lett contact of cam119, lower lett Contact Ot cam 116, right iront contact of relay 100 to ground through the upper right contact ot cam 111. This causes sequence switch 117 to move into position 12 and as hereinbetore described into position 17 where the` trip spindle magnet 122 is energized and the trip spindle is rotated to its normal position. Sequence switch 117 is then moved to position 1.

@all to P. B. X. Line group.

The operation of the switch to extend a connection to the lines of a private branch exchange group will now be explained. With such a group of private branch eX- change lines, it is necessary to cause the brushes to hunt automatically over the group of lines to select an idle line. It the tirst line is busy, the brushes must pass on to the second, etc., and stop upon the last line of the group whether idle or busy as explained hereinbetore. All but thev last line of the group are arranged with the resistance of their sleeve circuit the same as for an individual line. The last line ot the group has its sleeve or cut-ofil relay shunted by a resistance such as shown at 17 6, Fig. 3.

Should the brushes of the switch be moved upon the iii-st contact set ot thegroup of private branch exchange linesv and. this line be idle, the test relay 106 is energized in` position 6 when brush 145 makes Contact with terminal 148 and this relay remains energized. lVhen the sequence switch passes from position 6 to position 7, the-resistance 14:9 is included in this circuit, but the relay is so adjusted that it does not deenergizeand the call proceeds in the regular manner as betere explained tor a call to an individual line.

It, however, this lirst line of the group is busy, the test relay 106 is not energized in position 6 as the potential onthe test terminal 148 .is not sutiicient for its energization. Relay 100 is therefore energized in position 6 of the sequence switch 117 in a circuit from battery, winding ot relay 100, lower left cone tact oiI cam 150, switch 152 which is closed by the arm o1 the selector to ground at the back contar-t oit'relay 106. Relay 100, upon energizing, closes the circuit ot the brush carriage magnet 135, through the upper lett contact ot cam 136, right t'ront contact and armature of relay 100 to ground onthe right upper contact ot cam 111. The brush carriage magnet thereupon rotates until the brushes engage the contacts of an idle line, at which time brush 145 will encounter a test terminal suchasl 146 with sufficient potential thereon to energize the test relay 106. This relay upon energizing. opens the circuit rter relay 100, betere traced, which, upondeenergizing, opens the circuit: for the brush carriage magnet- 135 and brings the brushes to restonthe terminals et such idle private branch exchange line. Should the brushes ot' a switch hunt over ally the lines. otI the group and lind them busy and reach the last line in the group, the test relay 106 will be energized in positionG, inwhich position Y this relayis energizedor deenergized owing Tn the to the potentialiot'thextest terminal. case of a last line this potential is increased by a connection from battery through resistance 176 in parallel with the cut-olii relay 141-6 and the service meter 147 which are connected to the test terminal of the last line oit the private branch exchange group. This connection is illustrated in F ig. 3. It the last line of the private branch exchange group is bus, test relay 106 is deenergized when the sequence switch moves between positions 6 and 7 as resistance 149 is included in the circuit ot the testrelay. at this time..

lVhen relay 106 deenergi'z'es, relay 100 will be energized in aeireuit extending from battery through the winding of relay 100, lower lett Contact of cam 150, switch 152 to ground at the back contact of relay 106.

rI`he energization of relay 100 causes the sequence switch 117 to stop in position 9, as

`before explained, at which time the busy tone is connected to the calling line to inform the calling subscriber that all the lines in the group are busy. The release of the connection will then taire place, as described.

Ir", however, the last line of the group is idle, the potential ot the test terminal 148 is higher and the relay 106 is so adjusted as not to deenergize when the resistance 149 is included in its circuit, when the seque-ir. e switch moves between positions 6 and 7. This energization ot the test relay controls relays 142 and 100, which are deenergized in position 9 and the call progresses in the manner explained above.

Having thus described my invention I claim z l.`In a telephone exchange system, a selector switch comprising a plurality ot line terminals, brushes for cooperation with said terminals, means for moving said brushes to select a desired one ot a plurality ot said terminals, and means operated once only when said brushes are positioned upon a particular one ot said terminals to cause said brushes to be moved in a hunting movement over succeeding terminals.

2. In a telephone exchange system, a selector switch comprising a plurality ott line terminals, a brush arm, brushes carried by said arm :tor cooperation with said terminals, means for moving said brushes to select a desired one of a plurality of said terminals, and a switch operated once only by said arm when said brushes are positioned upon a particular one of said terminals to cause said brushes to be moved in a hunting movement over succeeding terminals.

3. In atelephone exchange system, a selector switch comprising a plurality ot line terminals, the first ones of said terminals being individual to subscribers lines, and the last ones of said terminals being associated with private branch exchange trunks, brushes for cooperation with said terminals,

means for moving said brushes to sel-ect a desired one oisaid first terminals, and means operated once only when said brushes are positioned upon the lirst one ot said lastterminals to cause said brushes to be moved in a hunting movement over suc ceeding terminals.

4. In a telephone exchange system, selector switch comprising a plurality ot line terminals, the irst ones or' said terminals being individual to subscribers lines and the last ones of said terminals being associated with private branch exchange trunks, a brush arm, brushes carried by said arm :tor cooperation with said terminals, means for moving said brushes to select a desired one of said first terminals, a cam on said arm, and a switch operable once only by said cam when the brushes are engaged with any of said last terminals, to cause said brushes to be moved in a limiting movement over said last terminals.

5. `In a telephone exchange system, a selector switch comprising a plurality ot rows of line terminals, brushes 'for cooperation with said terminals, means for moving said brushes to select a desired one ol a plurality ot" said terminals, and means operated once only when said brushes are positioned upon a particular one oi' said terminals in any selected row ot terminals to cause said brushes to be moved in a hunting movement over the succeeding terminals of the selected row.

6. In a telephone exchange system, a selector switch comprising a plurality or rows ot line terminals, a set of brushes for cooperation with each row of terminals, means for selecting a particular set of brushes and for moving the selected set of brushes to select a desired one of the terminals ot the selected row, and means operated once only when said brushes are positioned upon a particular one of the tern'iinals ot' a selected row to cause said brushes to be moved in a hunting movement over the succeeding terminals of the row.

In witness whereof, I hereunto subscribe my name this 21 day of August A. D., i924.

GERALD DE AKDT.

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