US1212809A - Telephone-exchange system. - Google Patents

Description

Patented Jm16,1917.

F. N. REEVES & A. E. LulwELL. TELEPHONE EXCHANGE SYSTEM. .f PPLICTION FILE SEPT- lrl. 1.95 1,212,809.

3 SHEETS-SHEET l.

un umm uu uuuuu ,s )muuuuuu g F. N. REEVES a. A. E. LuNnEL'L.

TELEPHoNE EXCHANGE sY-sTEM. E APPLICATION FILEDk SEPT. l l, 19l5. V

.Patented J an. 16, 1917.

`a SHEETS-#SHEET 2.

E s L Ef l 66 'MMM/ffy I F. N. REEVES & A. LUNDELL.

TELEPHUNE'EXCHANGE SYSTEM. APPLICATION FILED SEPT. l I. I9I5.

Patented Jan. 16, 1917.

UNITED STATES PATENT OFFICE.

FRANK N. REEVES, GF NEWARK, NEW JERSEY, AND ALBEN E. LUNDELL, OF NEW YORK, N. Y., ASSIGNORS, BY MESNE ASSIGNMENTS, TO WESTERN ELECTRIC COMPANY, INCORPORATED, A CORPORATION OF NEW YORK.

TELEPHONE-EXCHANGE SYSTEM.

Specification of Letters Iatent.

Patented Jan. 16, 1917.

To aZZ 'whom t may concern:

Be it known that we, FRANK N. Rnnvns and ALBEN E. LUNDELL, citizens of the.

This invention is preferably practised inA connection with systems in which the establishment of a connection is controlled by what is lgnown as the revertive impulse system of control: that is, in which the selecting 4`operations are controlled and accomanied' by impulses established in the seecting or fundamental circuit by the movement of a part, of the selector, which'impulses affect the sending or controlling apparatus until the proper. number of 1in-V pulses have been sent and the proper selection has been accomplished, when the controlling apparatus will in turn so affect the selector under control that' it will stop when 't e l proper selectiontis made. Thus in systems of this character the impulses, instead of passing from the sending or controlling apparatus to the selector under control, pass from the selector under control to the controlling apparatus.

According to an outstanding feature of this invention, a plurality of selector switches controllable from a sending station are controlled in their selective operation single relay associated with one of the selector switches. Y

' The invention will stood by reference drawings, wherein# Figures I1, 2 and 3 taken together are illus- -`trative of a system of circuits Vof a semiautomatic telephone exchange-system embodying the inventiong' Fig. 1 representing a calling telephone line and apart of an operator s connecting circuit equipment, Fig.

-2 the circuits of a trunk selector, and Fig'. 3 the circuitsoia final selector and a called telephone line.

be more fully underto the accompanying by aA The following description of the system illustrated in these drawings is written under the assumption that any form of selector mechanism and apparatus for the control thereof may be employed. In View of the fact that such equipment is not in itself a feature of the invention, for the sake of simplicity most of the details thereof are omitted, andthe various parts are not shown in their mechanical relation to each other.

The invention has been found useful in connection with automatic switches of the panel t pe as disclosed, for example, in patent to eynolds No. 1,058,903.

Assuming that a subscriber at station 100 is calling for subscriber at station 300: the operator first answers the call by inserting the plug 101 into the spring jack 102, then sets up on a well-known controlling or impulse receiving mechanism 103, the number representing the station wanted. Having set up the number, whatever it maybe, on the sender 103, a selector 104 is adjusted to extend the connectionto the proper district or oice in which the desired line terminates, whereupon the sender 103 is brought into circuit over the talking wires 105, 106 of theselected trunk by Way of the bottom contacts of sequence switch springs 107 and 108. The sequence switch springs shown in Fig. 1 are controlled by a well-known sequence switch (not shown), associated with selector 104, this sequence switch being moved into position 11 upon the adjustment ofselector 104. The sequence switch springs shown in Figs. 2- and 3 form a part of sequence switches 215 and 303 associated `with selector 200 and connector 302, respectively. Contact 109 of the sender is closed during the sending of impulses, and is opened for a-short period after the sending of 4a series of impulses. After the setting Iof selector 104, contact' 109 is closed to start the selecting control operation for a selector 200. A fundamental or selecting circuit is closed from the minus pole of battery, through the winding of a line relay 202, lefthand bottom contact of a sequence switch spring 203, left-hand top contact of sequence switch spring 204, resistance 205,

conductor 105, termmal 110 and wiper 1,11

of selector 104, bottom contact of sequence' switch spring 107, contact 109, winding of magnet 112, bottom contact of sequence switch spring switch spring 108, wiper 113 and terminal 114 of selector 104, conductor 106, top contacts of sequence switch spring 206 and resistance 207 to the lus pole of battery. Line relay 202 acts to cibse at its left-hand front contact a locking circuit by way of the lefthand top contact of sequence switch spring 203, so that this relay remains energized when its original path through sequence switch spr-ing 203 bottom opens. By reason of the c osing of the right-hand front contact o f relay 202 a circuit is closed from the plus polsini battery, bottom contact oi sequence switch spring 209, right-hand armature and'front contact of relay 202, the lefthand top contact of sequence switch spring 210 and thel winding of a trunk relay 211,

to the minus pole of battery. Relay 211 Acloses a circuit from the plus pole ofbattery lthrough its right-hand armature and front contact, the left-hand contacts of sequence switch spring 214, and the winding of the power magnet of sequence switch 215 to` the minus pole of battery, causing the sequence switch to advance from normal to position 2. Rela 211 also closes a locking circuit for'itself rom the minus pole of battery through its winding, left-hand front contact and armature, resistance' 217, test conductor 115` terminal 116 and wiper 117 of selector 104, resistance 118 and sequence switch spring 119, to plus battery.

In position 2 of the sequence switch 215 a circuit is closed from the plus pole of battery, through the bottom contact of sequence 209, the right-hand armature and front contact of line relay 202, the bottom contact of sequence switch spring 210 and the winding of magnet 220, to the minus pole of battery. Magnet 220 causes'the brushes of selector' 200 and commutator brushes 224, 225, 234, 250 to travel in a vertical direction. The selector brushes .are adapted to engage contacts of a terminal bank and the commutator brushes, commutator plates 223, 226, 235 and 261 respectively. Plates 223 and 261 are vcomposed of a conducting segment, and the other commutator plates of conducting and nonconducting segments. The sender stepping relay 112 is intermittently shunted, plus battery being connected to the right-hand top contact of sequence switch spring 203 through left-hand top contact of sequence switch spring 222, conducting segment 223, commutator brushes 224 and 225, and infterrupter segment 226. The number of nonconductive segments traversed by the commutator brush 225 on plate.226before the fundamental circuit is opened at109, is determined in this instance by the setting of the thousands register.

Upon the opening of the fundamental circuit at 109 and the sendingoutlof fthel last lrnpulse over plate 22S-line relay 202 reacts,

Under the control of magnet 220 the tripped -selector brushes and the commutator brushes opens the circuit of the lifting magnet 220 and. closes a circuit from plus battery through sequence switch spring 209 bottom, its right-hand armature and back contact, the left-hand armature and back contact of relay 230, the right-hand bottom and lefthand top contact of sequence switch spring 214 and the winding of the power magnet of sequence switch 215 to the minus pole of battery, to move the incoming sequence switch 215 out of position 2 into position .3, in which position a trip magnet 231 is operated by the closure of a circuit from the minus pole of battery through the winding of this magnet and the right-hand contacts of a sequence switch spring 232 to the plus pole of battery. Magnet 231 trips the desired set of brushes of selector 200. Theelevating magnet 220 becomes denergized when relay 202 reacts, and sequence switch 215 moves into position 3 and the selector and commutator brushes are arrested in their upward travel. After the sending out of the thousands impulses, contact 109 is again closed and the fundamental circuit established for again energizing relay 202, which then locks up in the above described manner. Upon the energization of relay 202 a circuit is closed from the plus pole of battery., through the bottom contact of sequence switch spring 209, the right-hand armature and front Contact of relay 202, the left-hand contacts of the sequence switch spring 233 and the winding of power magnet 215 to the minus pole of the battery, for moving the sequence switch from position 3 into position 4. In this position of the sequence switch a circuit `is closed from the minus polepf battery through the winding of the elevating magnet 220, bottom contact of sequence switch spring 210, the front contact and right-hand armature of relay 202 and the `bottom contact of sequence switch spring 209 to the plus pole of battery.

are'moved in a verticalfdirection for selecting the desired' group of trunks. The

stepping magnet 112 of the sender is again lCO intermittently shunted during. the upward' 115 travel ofthe brushes, plus battery being connected through the upper left-hand contact of sequence switch spring 222, conducting segment 223, commutator brushes- 224 and j 234, commutator segment 235 and therighthand bottom contact of sequence switch spring 203. After the selector has been ad- Justed, contact 109 is again opened, causing the denergization of line relay 202, whereu on a circuit is closed from the plus pole o battery, through the bottom contact of sequence switch'spring 209, right-hand armature and back Contact 0f line relay 202, theI left-hand armature and back contact of y ruayeaa the right-land bottom dien-1 from the minus pole of battery, through the lettfhand winding of test relay 230 and the lelthand top and right-hand bottom con tacts of sequence switch spring 232 to the ductors 301, z'. e., over trunks its fourth position,

` to final selector switches 302,

'minus pole of battery.

hand top contact of sequence switch Ispring 214:, and the winding of the power magnet of sequence switch 215 to the minus pole of battery 216, for moving the sequence switch out of position 4 into position 5. When relay 202 reacts and sequence switch 215 leaves the circuit of magnets 220 and 231 is opened and the selector brushes are arrested on the desired group of trunk terminals. A circuit is now closed plus pole of battery. Relay 230- becomes energized and, by attracting its left-hand armature, closes a circuit from the plus pole of battery through the bottom contact of sequence switch springA 209, right-hand ar mature and back contact of line relay 202, left-hand armature and front contact of relay 230, the let`t-hand contacts of sequence switch spring 233, and the winding of the power magnet of sequence switch 215 to the minus poley of battery, forl moving the sequence switch out of position 5 into posi tion 6.

In position 6 yof thesequence switch, a

circuit is closed from the minus pole of battery, througxh the winding of elevating magnet 220, t e bottom contact of sequence switch spring 210, lthe left-hand front contact and armature-of' relay 230, the righthand back contact and armature of relay`202 and the bottom contact of sequence switch spring 209 to the plus pole of battery. Magnet 220 causes over. the terminals of the selected group of trunks. Aslongas brush 236 of selector 200 travels over the terminals of busy trunk con on which full potential exists and which lead the associated Sequence switches of which are in aii-onormal position, the test relay 230 finds a circuit from plus battery, through sequence plus battery switch spring 304, the right-hand back con# ance 237 (or from .plus battery, through the topvcontacts of sequenceA switch spring-222 of other selectors), the right-hand armature and front contact of relay 230, the bottom contact of sequence switch `spring 238 and the right-hand winding of relay 230 to the As soon, however, 200 reaches the terminal of an idle trunk conductor 301, no such circuit is found for relay .230, and this relay becomes denergized, openingv at its left-hand armature the 'energizing circuit of magnet 220, and closing a circuit from the minus pole of battery through the winding of the power as selector magnet of sequence switch 215, the left-hand bottom contacts of setop and right-hand quence switch,

the selector brushes to hunt x quence switch spring 214, the back contact and left-hand armature of relay 230, the righthand back contact and armature of relay 202, andthe bottom contact of sequence switch spring 209, to the plus pole of battery, for moving sequence switch 21.5 into position 7. In this position of the the fundamental circuit will again be closed for causing the energization of relay 202, which closes at its righthand armature and front contact a circuit tt rough the lefthand contacts of sequence switch spring 233 for sequence switch 215 and moves the same into position 8. ln position 7 of the sequence switch, the test terminal of the selectedtrunk is rendered busy by a plus battery connection through the top contacts 'of sequence switch spring 222, resistance 237 and selector brush 236.

ln position 8 of the sequence switch, line relay 202 remained energized by a'locling circuit closed through its left-hand front contact andarmaturc and the left-hand top contact of sequence switch spring 203. This relay further closes a circuit from theininus pole of battery through the winding of line relay 306, lefthand bottom and right-hand top contact of sequence switch spring 307, trunk conductor 308, brush 2&0 of selector 200, the right-hand top contact of sequence switch spring 210, the right-hand front contact and armature of relay 202 and sequence switch spring 209 to the plus polel of bat tery. Relay 306 becomes energized and closes a circuit from plus battery through its left-hand armature and front contact, the

right-hand top and left-hand'rbottom con- 'the right-hand top contact of sequence 311, and the power magnet switch spring y of sequence switch 303 to the minus pole of battery, for moving this sequence switch out of its normal position into position 2. `In position 2 of the sequence switch 303, relay 306 is maintained energized by a locking circuit closed from the minus pole of battery, through its winding, top contact of sequence switch spring 312, front contact and armature of relay 306 and the top contacts of sequence switch spring 307 to plus battery at sequence switch spring 209. In this position of the sequence switch, a circuit is closed from the minus pole of battery through the winding of magnet 3 13, bottom contact of sequence switch spring 312, the right-hand armature and front contact of relay 306, the top `contacts of sequence switch spring 307, and then in parallel with the circuit of relay 306 to the plus pole of battery at sequence switch springV the right-hand pulses from connector 302, the fundamental circuit .is opened at contact 109. Relay 202 becomes denergized and closes aclrcuit through sequence switch spring 214 for driving lsequence switch 215 out of position 8 into position 9. Relay 202 opens the circuit of relay 306, which in turn closes a circuit from plus battery, through its left-hand armature and back contact, left-handtop and righthand bottom contact of sequence switch spring 310, and the power magnet of sequence switch 303 to minus battery for moving this sequence switch out of position 2 into position 3. The energizlng circuit or magnet 313 is now opened at the front contact of rela-y 306 and sequence switch spring 312, and a magnet (not shown) causes now the tripping of the desired set of brushes of connector 302. Upon the next closure of the fundamental circuit at contact 109, relay `202 becomes again' energized and closes a circuit over the left-hand contacts of sequeiice switch`spring 233 for moving sequence switch 215 out of position 9 into 10. The original energizing path of relay 306 is again established, and this relay again closes the circuit over the right-hand contacts of sequence switch spring 310 for driv ing sequence switch 303 into. position 4. In this position ofthe sequence switch, the energizing circuit for magnet 313 is again established over sequence switch sprin 312, and the connector is -moved to select t e desired tens After'the sending of impulses the fundamental circuit is again opened at 109 whereupon relays 202 and 306 react, the latter closing a circuit overthe left-hand top and right-hand 'bottom contact of sequence switch spring 310, for driving se,-

' quence switch 303 out of position 4 into 5,

finto positions 12 andr4 elevating magnet 3131s again iquence switch 312being'closed. Durand the former over vsequence switch spring 214 for moving sequence switch 215into po- 'sition 11. In position 5 of sequence switch 303 the' circuit of magnet 313 yis again opened at the :troutv contact of relay 306 and sequence switch spring 312. Upon Ythe next closure of the fundamental circuit, rela s..

202 and 306 become energized, causing t e driving of sequenceswitches 215` and 303 respectively, The

` energized, se-

ingfthe upward travelofftle selector brushes,

the stepping magnet.1 12"`ofthe sender is inling of relay ducting segment 315, commutator brushes i 314 and 316,y interrupter segment 317, the

fai

right-hand top contact of sequence switch spring 320, the right-hand top contact of sequence switch spring 321, trunk conductor 322, and the left-hand contacts of sequence switch spring 204, in the same manner as was described with the adjustment of se` lector 200. After the last series of impulses have been, sent back to the sender, Contact 109 is again opened and relays 202 and 306 become denergized, causing the stepping of sequence switches 215 and 303 into positlons 13 and 7, respectively,.and the opening of the circuit of magnet 313. Upon the sending out of the last series of impulses, the sequence switch controllin springs 107, 108 and 119 are Vmoved out o? position 1l into position 14, whereupon 'a circuit is closed 'from ground at repeating coil 120, through 107, 111, 110, 105, 204, -203 and 202 to grounded battery.

Relay '202 upon energization closes the driving `circuit through vsequence switch spring 233 for moving sequence switch 215 out of position 13 into position 15, whereupon the circuit of relay 202 is opened lat 204. Relay 306 is again energized by a circuit closed from the minus pole ofba'ttery, through its winding, left-hand bottom and right-hand top contact ofsequence switch spring 307, conductor 308, brush 240, contact 241 of relay 242, the right-hand contacts of sequence switch spring 204, conductor 105, terminal 110, wiper 111 and the top contact of sequence switch s ring 107, to ground at repeating coil 120. IRelay306 upon energization, closes a circuit through the righthand contacts of sequence switch spring 310 for driving sequencev switch 303 out of position 7 into position 8, in which position a circuit is closed from ground, through `the high resistance winding of a marginal test relay 323, the bottom contacts of sequence switch spring 324, the low resistance wind- 323, sequence vswitch lsprin 325, test wiper 326 of connector 302,A an the vwinding of a. cut-off relay 330,' associated with the called line to Supposing that the calle therefore that full battery lgrounded battery. line is idle, and potential exists von the multiple test terminals thereof, the

above traced circuit causes the energization I of test relay 323, which in turn closes a locking circuit for itself from ground, through f "the rightfhand armature and back contact of relay 331, and its upper.' armature, front contact -and low resistance winding. Relay 323 closes a circuit fromA plus battery through the left-hand armature and back contact of relay 331, the lower armature and front contact of relay 323, the right-hand bottom-conloo tact of sequence switch spring 311 and the winding of the power magnet of sequence switch 303, to minus battery, and the sequence switch is moved out of position 8 and `through position 14 into position 16, in

sequence 'switch spring 222, conducting seg ment 223, commutator brushes 224 and 250, conducting segment 251, the top contact of sequence swtchfspring 238 and the right-A hand winding of the test relay 230 to the minus pole of battery, and another vcircuit yfrom plus battery through the bottom? and left-hand top contacts of sequence switch spring 232 and the left-hand winding of re-V lay 230 to the'minus pole of the battery. This relay becomes energized and when sequence switch 215 is moved to position 15, a circuit is closed from the plus of battery through the top contacts of sequence switch spring 222, the right-hand .armature and front contact of 'relay`230, the right-hand bottom contact of sequence switch spring 252 and `the power magnet of sequence switch 215 for moving this sequence switch into position 16, whereupon relay 230 becomes denergized.

A circuit is now closed `from the minus pole of battery, through the top contact of sequence switch spring 209, the right-hand armature and lbaclr contact of relay 202, left-hand armature'and back 'contact of relay 230, the right-hand 'contacts of sequence' switch spring 214,"windin'gs of relays 243 and 242, contact 244 of relay 245, sequence switch spring ,246 and trunk conductor 105 to ground atrepeating coil 120. Only relay 242 becomes energized, a shunt existing around the winding of relay 243 from the armature and back contact of relay 247, the back contact and armature of thei'elay 243, the winding of this relay, and back to the armature and back contact of relay 247. Ringing current is applied to the called line, a circuit being closed from' ground through an alternating ringing current source 254, the winding of relay 247, sequence switch Vspring 255, the lower front contact and armature .of relay 242, the calling subscribers loop, and back to ground through the upper armature and contact of relay 242. As soon as the subscriber at the called. station 4removes his receiver from the switchhook, re-

lay 247 becomes energized, and .by opening the shunt around the winding of relay 243,

causes the energization of this relay, which` the ringing current from the called line. As a further result of the response ofthe called subscriber, supervisory relays 256 and 121 become energized, and the former, by attracting its armature, connects relay 245 parallel with relay 243, which will be maintained energized during conversation by a circuit extendin from groundthrough the armature and ront contacti'of relay 245, the front contact, armature and winding of relay 243, the right-hand contacts of sequence switch spring 214, the back Contact and leftf hand armature of relay 230, the right-hand back contact and armature of relay 202, and the top contact of sequence switch spring 209, to the minus pole of battery.

When sequence switch 303 moved through position 15 into position 16,'a circuit was closed from ground through sequence switch spring 334, the winding of relay 331, sequence switch spring 325, connector wiper 326 rand the winding of relay 330 to the minus pole of battery.. Relay 331 became energized and, byY attracting its ri lit-hand armature, closes a locking circuit or itself and opens the circuit of relay 323. The

called line is held by this circuit closed through relay 331.

' Upon the restoration of the receiver at the `called station 300, relays 121, 256, 245 become denergized. Relay 121 actuates a well-known supervisory signal (not shown), whereupon the operator causes the restoration of selector 104, and the sequence switch associated therewith. The locking circuit of relay l211 is opened thereupon, and this relay, by releasing its right-hand armature, closes a circuit from' theA plus pole of battery through its right-hand armature and back contacts, the left-hand top contact of sequence switch spring 252, and the winding of the power magnet of sequence switch 215 to the minus pole of battery for driving this` sequence switch out of position 16 through position 17 into position 18. In this position of the sequence switch a circuit isclosedA from the minus pole of battery through the winding of down magnet 257 and the bottom contacts of sequence switch spring 260 to the plus pole of battery. Under the control of magnet 257, selector 200 is restored to normal, whereupon a circuit is closed from the plus pole of battery through the left-hand top contact of sequence switch spring 222,.,conducting segment 223, com-` mutator brushes 224 and 234, conducting segment 261, the left-hand bottom contact of sequence switch spring 252, and the winding of the power magnet of sequence switch 215 to the minus poleof battery for driving sequence switch 215 out of. position 18 into` its normal position. Uponthe release of selector 2400 the locking circuit of relay 305 is "opened and this relay closes a circuit from plus battery through its left-hand armature 303 to the minus tom contact of sequence switch of sequenceswitch 303 to the minus pole o fbjattery, and thisA "ito its normal position.

andr'back contact, the left-hand top contact spring 311, and the windpower magnet of sequence switch pole of battery for drivin the sequence switch out' of position 16 an through position 17 into position 18.

A circuit is closed from' the minus pole of battery throu h the winding of magnet 335, and the right-liand top and left-hand bottom contacts of sequence switch springm318 to plus battery. "Under ,the control of'niag'net 335 connector 302" isJ restored to normal. When connector'i302 reaches its normal position, a circuit is closed fromplus battery through the left-hand bottoni contact of seof sequence switch ing of the quence switch spring 318, conducting seg-l ment 315, commutator brushes v314 and 336, conducting segment 337, the left-hand botspring 311, and the power magnet sequence switch is movedout of position 18 upon' becomes de nergized. All the apparatus employed ingthe buildingr upof the connection is restored to normal, the operator having removed her plug 101 upon the Y receipt of a well-known clearing-'oufsgnal (not shown) 'controlled by relays -121 and 122, thelatter being denergized upon 'the restoration of the receiver at the callingstation. If the called subscribers line is found busy,relay 323 will notbecoine energized, due tothe lack of full battery potential on the test terminal of this line. Relay 306 becomes energized by a circuit from the minus pole of battery, through its winding, the lefthand top contact y of sequence switch spring 321 (sequence switch 303 being in position 8), the right-hand bottomv contact of sequence switch spriig 320', the loweil back contact and armature of relay 323, and the left'hand, back contact and armature ofrelay 331 to plus battery. Upon the energization of relay 306 a circuit is closed from plus battery through the left-hand armature and front contact of -this relay, the right-hand contacts of sequence switch spring 310, and the power magnet of sequence switch 303`to the minus poleoff battery for moving the sequence switchout of position 8 and into position 14, inwhich .position a circuit is closed from the minusV pole of battery through the winding of the magnet 335, sequence switch spring 340, the lower armature and back contact of relay 323, and the oplei of thll pltent my be obtained for ave cents each, by addressing the operating with said d shunting saidY stepping left-handpback'contact and armature of relay 331 to plus battery. Under the control of magnet 335 the switch is released to normal. Upon the release of this switch, plus batis connected through brush 336, segment 337, and the left-hand bottom Contact of sequence switch spring 311 to the power magnet of sequence switch 303, and this'se- Vquence switch is moved into position 17, in

whereupon selector yrality of automatic power-driven switches for interconnecting said lines, driving circuits for said switches, and a sender for controlling the operation of said switches by means of revertive impulses, of a single relay to coperate with said sender for directly controlling the driving circuit of each switch in succession. Y

2. In a telephone exchange system, the combination with a plurality of lines, a plu` rality of automatic for connecting said es, driving ma ets for said switches, circuits' for energizing said magnetsfand a sender for controlling the operation of said switches by means of revertive impulses, of a single relay co- 'sender and controlling at a front contact the magnet energizing circuit of each switch in succession.

3. In a .telephone exchange system, the combination with a plurality of lines, a plurality of automaticswitches for interconnecting the same, and a fundamental circuit comprising a stepping relay and a control relay `for jointly supervising the operation of each of sociated with each switch for intermittently relay but maintaining energized said control relay during the advance; of its aociated switch. In witness whereof, we hereunto sub.- scribe our names this 8th day of September A. D., 1915. Y

FRANK N. REEVES.

ALBEN E. LUNDELL.

"GQIIIMMSOMI' o! Patents.

walhlngtonfh. 0,

ower-drivn switches said switches, of a commutator as!

Images