US1291960A - Number-indicating system. - Google Patents

Description

A. E. LUNDELL.

NUMBER INDICATING SYSTEM.

Patented Jan. 21,1919.

4 SHEETS-SHEETI when E. Luhde/Z APPLICATION FILED SEPT 22, 1916- A. E. LUNDELL.

NUMBER INDICATING SYSTEM.

APPLICATION FILED SEPT. 22. I916.

1,291,960. Patented Jan. 21, 1919.

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A. E. LUNDELL.

NUMBER INDICATING SYSTEM.

APPLICATION FILED SEPT. 22, mm.

A. E. LUNDELL.

NUMBER |ND|CAT|NG SYSTEM. APPLICATION FILED SEPT. 22. 1916. 1,291,960, PLtGIltGd Jilll. 21, 1919. 4 SHEETS-SHEET 4.

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ALBEN e. LUNDELL, on NEW YORK, N. Y., ASSIGNOR T0 WESTERN ELECTRIC COMPANY,

INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

NUMBER-INDICATING SYSTEM.

Specification of Letters Patent. Patentgd J an 21, 1919 Application filed September 22, 1916. Serial No. 121,564.

To all whom it may concern:

Be it known that I, ALBEN E. LUNDELL, a citizen of the United States, residing at New York, in the county of Bronx and State of New York, have invented certain new and useful Improvements in Number-Indicating Systems, of which the following is a full,

clear, concise, and exact .description.

This invention relates to telephone exchange systems, and more particularly to systems of the type employing machine switching.

It is an object of this invention to provide an improved means for informing a final connecting operator of the number of the wanted line by means of an automatically operated indicating device.

A further object is to provide an arrangement by which a relay may be used to control the deenergization of a power magnet, means being present to prevent a harmful spark at the relay contact.

A feature of the invention is the utilization of both sides of a trunk for impulse sending, impulses of various lengths being sent simultaneously, the impulses over one side of the trunk also being used to operate a step-by-step switch.

An additional feature is the provision of a combination of fast and slow relays actuated by the impulses sent over the line,

circuits being completed at contacts of these relays to certain ones of a combinationof relays over wipers controlled by a step-bystep switch.

A further feature of the invention has to do with the control of a selective switch, and consists'in closing the operating circuit of the power magnet through a normally closed contact of the switch. After the switch leaves its normal position, a comparatively high-resistance holding circuit is maintained at a relay contact. A condenser is bridged across the windings of the magnet in order to reduce sparking at the relay contact when the holding circuit is broken. This condenser would normally make the magnet too sluggish in releasing for reliable operation of the switch, but since only sufficient current is flowing in the circuit to hold the magnet energized, it will be quick to release in spite of the condenser.

The invention has been shown applied to atelephone exchange system of the wellknown semi-automatic type, but is obviously capable of arrangement for use in other systems.

his thought that the invention will best be understood from the following detailed description, reference being had to the accompanying drawings.

In the drawings, Figure 1 represents the substation apparatus of a calling subscriber and an A operators connecting cord circuit, together with a selector switch for extending the calling line to a trunk leading to a B operators position. In Fig. 2, portions of a connecting circuit at the B operators position are shown, together with the substation line and apparatus of a called subscriber. In the lower portion of Fig. 2 is indicated a step-by-step switch to control the call indicating device. Fig. 3 shows the relay combination controlling the lighting of the number indicating lamps. Fig. 4 shows diagrarmnatically the A operators sending device and the circuits of a cord finder switch for associating such sender with a cord circuit. The previously mentioned switch controlling means have been shown applied only to the switch indicated in Fig. 1. Fig. 5 is a diagrammatic representation of the code of impulses by means of which the indicating device is operated to set up various number combinations.

When the subscriber at substation 10 desires a connection, he removes his receiver from the hook, causing thereby the display of line signal 12 by the operation of line relay 13 in the well-known manner. An operator, one of whose cord circuits is indicated at 0, upon observing the lighting of the line signal 12, inserts a plug 1 1 into a jack 15 associated with signal 12. A circuit is then completed from groundedrbattery, winding of cut-oft relay 16, sleeve contact of jack 15, sleeve of plug 14, winding of relay 17 to ground. Relays 16 and 17 are energized in this circuit. Relay 17 completes a circuit from ground, armature and front contact of relay .17, listening-key sequence switch contact 18, winding of power magnet 19 of the listening-key sequence switch, to grounded battery. The listening-key sequence switch moves from position 1 to position 7 under the control of normal spring 20.

In position 7 of the listening-key sequence switch, the operators head set 21 is connected to the talking strands of. the connecting cord over listening-key sequence switch contacts 22 and 23. The operator may now converse with the calling subscriber and ascertain the number of the wanted line. The operator then'depresses listening-out key 24, whereupon a circuit is completed from ground, contacts of key 24, listening-key sequence switch contact 25, winding of power magnet .19, to grounded battery. The listening-key sequence switch moves from position 7 into position 11.

It is to be noted that if the operator plugs in another cord, the operation of. the listening-key sequence switch indicated at 19 will complete a circuit from ground through contact 26 of such second listening-key sequence switch, and contact 27 of the first listeningkey sequence switch to power magnet 19, for moving this switch from position 7 into position 11, and the operators set is thus automatically disconnected from the first cord.

When the listening-key sequence switch arrived in position 7, a circuit was completed from ground, listening-key sequence switch contact 28, connecting cord sequence switch contact 29, winding of the power magnet30 of the connecting cord sequence switch, to grounded battery. The connecting cord sequence switch thereupon moves from position 1 into position 2.

In position 2 of the connecting cord sequence switch, a circuit is completed from ground, connecting :cord sequence switch contact 31, cord finder sequence switch contacts 32-and 33, winding of relay 34, to grounded battery. Relay 34 is energized and completes a circuit from ground, left-hand armature and front contact of relay 34, cord finder sequence switch contact 35, winding of the power magnet 36 of the cord finder sequence switch, to grounded battery. The cord finder sequence switch then moves from position 1 into position 2 under the control of its normal spring 7 In position 2 of the cord finder sequence switch, acircuit is completed from grounded battery, winding of power magnet 38, cord finder sequence switch contact 39, commutator segment 40 and brush 41, conductor 42, cordfinder sequence switch contact 43, to ground at the left-hand armature and front contact of relay 34. Upon the energization of the updrive magnet 38, a brush set 44 is moved upward by the action of constantly rotating roller 45. After brush 41 moves out of engagement with segment 40, a holding circuit for up-drive magnet 38 is completed through cord finder sequence switch contacts 39 and '46,- resistance 47, to ground at the left-hand armature and front contact of relay 34.-

When the brush set 44 arrives on the terminals of a cord in a condition to be seized, a circuit' will be completed for test relay 48 from grounded battery, cord finder sequence switch contact 49, brush 50, terminal 51, connecting cord sequence switch contact 52, to ground. Relay 34 has been maintained energized over a circuit from grounded battery,

winding of relay 34, cord finder sequence switch contacts 33 and 53, to ground at the armature and back contact of relay 48. lVhen a brush 54 is passing over conducting segments of a commutator 55, an alternative circuit is completed for relay 34 through its right-hand armature and front contact, conducting segments of commutator and brush 54, cord finder. sequence switch contact 43,to ground at the left-hand armature and front contact of relay 34. When relay. 48 energizes, the first of the above traced. circuits is broken at its right-hand armature, and when brush 54 engages an insulating segment of commutator 55, which occurs when. the brush set 44 is centered on the terminal set of the desired cord, relay 34 is deenergized and opens at its left-hand armature the holding circuit of u'p-drive magnet 38. This holding circuit was carrying comparatively little current due to the presence of resistance 47 and therefore may be broken without causing a harmful spark. To further minimize the spark at the lefthand armature of relay 34, a condenser 56 is connected in parallel with the windings of magnet 38.

The left-hand armature of relay 34 complates a circuit from grounded battery, winding of power magnet 36, cord finder sequence switch contact 57, left-hand armature and back contact of relay 34 to ground, whereupon the cord finder sequence switch moves from position 2 into position 3.

lVhen relay 48 energized, it completed a locking circuit for itself from grounded .battery, winding of relay 48, cord finder sequence switch contact 58, left-hand armature and front contact of relay 48, brush 59, terminal 60, relay 61, connecting cord sequence switch contact 62 to ground. Relay 61 is energized in this circuit and completes a circuit from ground through its armature and front contact, connecting cord sequence switch contact 63, winding of power magnet 30 to grounded battery. The connecting cord sequence switch then moves from position 2 into position 3.

After the operator learned the number of the wanted line, she depressed keys in a key set (not shown) to control the selection of'a trunk leading to a B operator at whose position connection to. the wanted line may be made. She also depressed keys in akey set S, which keys control a'numbelindicating device at the B operators position to in form her of the number of the wanted-line. The manner in which the key set (not shown) operates to controlthe selection of a trunkleading to a B operator is preferably similar to the arrangement shown in Patent quence switch,

contact completes a' circuit 1.3 and into position 1. In

'77, connecting cord sequence 7 8 to ground -ord sequence In position 3 of the connecting cord sea circuit known as the fundamental circuitis completed from grounded battery, winding of relay 6%, connecting cord sequence switch contact 65, conductor 66, terminal 67, brush 68, cord finder sequence switch 69, armature and back contact of relay 0,.the winding of stepplng relay 70,

' finder sequence switch contact 71, brush 72,

terminal 73, conductor 74, connecting cord sequence switch contact 75 to ground. Relay 64L at its right-hand armature and front from ground through connecting cord sequence switch contact 76, the winding of power magnet to grounded battery, for moving the connecting cord sequence switch out of'position osition 4, a circuit is completed for up-c rive magnet 77 from grounded battery, winding of magnet switch contact at the armature and front contact of relay 64.. In response to the energization of magnet 77, brush set 79 is then moved upward under the control of the constantly rotating roller 80, in the well-known manner.

A brush 81 passes over conducting segments of a commutator 82 to shunt out the circuit of the stepping relay 7 0 over a. path from connecting cord sequence switch contact 83,, conductor 84, conducting segments of commutator 82, and brush 81 to ground, it being understood that relay 64 locks itself to conductor 66 through its left-hand armature and front contact and connecting switch contact 85. The intermittent shunting out of the stepping relay 70 causes the successive actuation of the counting relays in the well-known manner.

flll hen relay 0, known as the upper zero counting relay, has been energized and brush 81 encounters an insulating segment, the circuit of relay 64 is opened and it is deenergized, opening at its right-hand armature the, circuit of up-drive magnet 77. The brushset 79 therefore is brought to rest in a predetermined position which is at the bottom of a certain group of terminals of the contact bank.

,Theright-hand armature of relay 6% at:

its back contact completes a circuit from ground through connecting cord sequence switch contact 86 and the winding of power magnet 80 to grounded battery, for moving the connecting cord sequence swit h out of position sand into position 5. The energization of the relay 0 completed a circuit from the ground, cord finder sequence switch contact 87,. the winding of power magnet 36 of position 3 and int position 5.

In'position 5 of the connecting cord sequence switch, the fundamental circuit is the steppin shunted out lay the cord again established through relay 64 and this relay again attracts its armatures, thereby moving the connecting cord sequence switch out of position 5 and into position 6, in amanner similar to that previously described.

In position 6 of the connecting cord sequence switch, power magnet 77 is again energized, causing the brush set 79 to be advanced over the desired group of terminals, relay being intermittently y the action of a brush 88 over a path from connecting cord sequence switch contact 89, conductor 90 conducting segments of a connnutator91, and brush 88. to ground. When the upper zero counting reis again energized and brush 88 encounters an insulating segment of commutator 91, the circuit of relay 6% is broken. Re lay 64 is de'e'nergized, opening at its righthand armature the driving circuit of magnet -7 7, and the brush set isbrought to rest at the bottom of a group of trunks leading to the desired operators position. Relay or, at its right-hand armature and back contact, completes a circuit from ground through connecting cord sequence switch contact 86 and the winding of power magnet 30 ;to grounded battery, for moving the connect- .ing cord sequence switch out'of position 6 through its right-hand armature andfront contact, cord finder sequence switch contact 87 and the winding of power magnet 36 to grounded battery, for moving the cord finder sequence switch out of position. 5 andinto 1 position 7 After the brush set 7 9. was positioned on the terminals of a trunk leading to a desired B operators position ;over the trunk terminating at O, and the connectingcord sequence switch arrived in position 11, a circuit was completed from. ground, the, winding of relay 92, cord finder sequence switch contact 93, brush 7 2, terminal- 73, conductor 74, connecting cord sequence switch contact 94, brush .95, terminal 96, trunk conductor 97, lower contact 98 of a key K, upper left-hand winding of a repeatingcoil 9.9, and the winding of relay 100 to grounded battery. The energization of relay 92 completes acircuit from grounded battery, windmg of relay 101, armature and front contact of relay .92 to ground, Relay 101 is energize d and locks itself to ground through its left-hand armature and cord finder sequence switch contact 102. i i The energization of relay 100 completes a circuit from grounded battery through a signal lamp 103, conductor 104, armature and-front contact of relay 100, armature and back contact of relay 105, 're'sistancej106, to ground. Lamp103 is lighted and indicates to the-B- operator at Othat 'a call-is being extended over a trunk terminatingin aplug1'07jassociated with the signal 103. She then depresses key K and maintains it depressed until the lighting of the number indicating lamp informs her that ail-the impulses, have been sentfrom sender S. The operation of key K removes the-battery connection from trunk conductor 97 and results in the deenergization ofrelay 92, whereupon a circuit is completed from ground, armature and back contact of relay 92, righthand armature and front contact ofrelay 101, finder sequence switch contact 108, the windingcof power magnet 36 to grounded battery, for moving the cord finder sequence switch out of position 7 and into position 19. The cord finder sequence switch varies from the usual structure in that. it has twenty positions instead of the usual eighteen. w a

The/relay combination shown in Fig. 3 andthe key setfindicate'd at S are arranged for indicating numbe'rs of two digits only, although it, is obvious that the system is capable of expansion to indicate any desired number of digits "at the B operators position. Assuming now that the number of the Wanted line is 13, the operator at 0 will depress key 1 in the tens column and key 3 in the units column. The operation of the number indicating device will then be as follows. When the sender sequence switch passes through position '8, an impulse will be sent from grounded battery, resistance 109, conductor 110, closed'contactoffthe tens 'kefy No. 1,"conductor 111, cord finder "sequence switch contacts 112 and '71, brush 72, terminal 73, conductor 74, connecting cord sequence switch contact 94, brush 95, terminal '96, trunkconductor 97, contact 113, and the windings ofrelays 114 and .115 to ground. Sincefthis circuit is closed only while "the cord finder sequence swit h is passing through position 8, this impulse is of short duration, and relay 114'b'eing slow to, pull up will not be actuated. Relay 115, however, actuated in fitliis circuit.

At the same time,'ani'm'pulse will be sent over the {lower side of the trunk "from ground, conductor 116, clo'sedjcontact of tens key No. '1, conductor117, connecting cord f quenc'eswitchcontacts '11'8and 69, brush 68, 'tfminal nductor '66, connecting cord sequence; switch. contact. 11 brush 1%, ",t er- 'rnina1'121, trunk con'dutor 122, contact 123 1 finder sequence switch contact '143, "relays 1'24 and 125 to grounded battery.

of key K Winding of relays 124 and 125 to grounded battery. This impulse is of. longer duration, since the circuit is closed from position 8 to position 10.0f the -cordQfinder sequence switch, and relay 124, although slow to pull up, is energized in series with quick-acting relay 125.

When relay 125 is energized, a. circuit is completed from grounded battery, stepping magnet 126 of a rotary step-byf-ste'p switch, wiper 127 and its first contact, armature and front contact of relay. 125 to ground. The stepping magnet. 126 then moyes the wipers 127, 128, 129, 130 and 131 into engagement with their second contacts. In this position of the controlling switch wipers, a circuit is completed for relay 132 from grounded battery, winding of relay 132, conductor 133, wiper-129, to ground at the armature and front contact of relay 115.. Relay 132 locks itself to conductor 134, which is grounded at contact 135 of key K. A circuit is also completed for relays 136 and 137 from grounded battery, windings of relays 1'36 and 137, conductor 138, wiperr1'30 and its second contact, to ground at the armature and front contact of relay 124 which was energized by the long impulse over the lower side of the line. The actuationof relay 137 completes a lockingcircuit for relays :136 and 137 to grounded conductor 134. Offnormal contact 149 is closed, but the switch does not interrupt its own circuit and continues stepping, since this branch circuit is held open at the armature of a relay 139.

which was energized through contact 135 of key K when such key was first depressed. Since relay 114 was not energized by the first pair of impulses coming in over the trunk, the relay controlled by the wiper128' in its second position will not be energized. When the cord finder sequence switch leaves position 10, relay 125 is deener'giz 'ed, completing a circuit from groundedbattery, winding of stepping magnet 126, wiper 127 and its second contact, to ground at thefarmature and back contact of relay 125. The

controlling switch then moves its wipers to 'position 3.

lVhen the cord finder sequence switch arrives in position 12, another pair of impulses f'sequence switch contact 142, "to ground through relays 114 and 115, relay 115- only being energized, The, impulses over the lower side of the "line will also be o'f "short duratiomthe circuit being from .ground,1cord through Thegoperation of relay 125 causes the controlling switch wipers to be moved from their third into their fourth positions in a manner similar to that previously described, whereupon a circuit is completed for relay 144 from grounded battery, conductor 145, wiper 129 and its fourth contact, to ground at the armature and front contact of relay 115 Since both these impulses were short, no "circuits will be completed over wipers 128 and 130, relays 114 and 124 not having been actuated. When the cord finder sequenceswitch leaves position 12, relay 125 is denergized and .the controllingswitch moves-its wipers from the fourth to the fifth position, in themanner similar to that previously described. When the cord finder sequence switch arfves in position 16,another pairof impulses will be sent over the trunk line, the impulse over the upper side of the line being of short duration,;since circuit iscompleted only in position 16 of the cord finder sequence switch,- such circuit being from grounded battery, resistance 109, conductor 146, closed contacts of unitskey No.. 3, conductor 147, cord finder sequence switch contact 148, to groundthrough relays 114 and 115', relay-115 only being actuated. The impulse overthe lower side of the line will also be of-short durationandmay be traced from ground, cord finder sequence switch contact 143 to grounded battery through relays 124 and 1 25 1 The actuation of relay 125 moves the controlling switch wipers from position 5 to position 6, at which time a circuit is completed for relay 150 from grounded battery, conductor 151,.wiper 129' and its sixth contact, to ground .at the armature and front contact of relay 115. Belay 150 locks up to grounded conductor 134. When the cord finder, sequence switch contact leaves position 16. relay 125 is denergized and the con trolling switch moves its wipers into their seventh position. Relay 152 was energized when conductor 134 was first grounded over a path from grounded battery, winding of relay .152, armature and back contact of relay 153 to conductor 134. Similarly, relay 154 was energized over a circuit from grounded battery, winding of relay 154, armature and back contact of relay 156 to conductor- 134. When wiper 131 arrives in its seventh position, circuits are completed for lamp-1 of the tens group and lamp 3 of the units group to indicate to the B operator that line No. 13 is desired. The circuit of lamp .1 of the tens group may 'be traced from grounded battery, through lamp 1', inner right-hand armature and front contact of relay 137, inner righthand armature and 'back contact of relay 153, outer right-hand arma=- ture and front contact ofv relay 132, andright-hand, armature and front contact of' relay 144,- c'onductors:15'(, 158, wiper 1 31 to 5 ground, The circuit of units lamp 3 may be traced from grounded battery, through lamp 3, outer right-hand armature and back contact of relay 159, outer right-hand armature and back contact of relay 156, inner righthand armature and frontcontact of relay 150, right-hand armature and back contact of relay 160, conductor 158 to ground as described. v

Itis to be noted that at this time no other lamps in the tens group can be lighted, since the circuits of lamps 3, 5, 4 and 2 ar'e'maintained-opcn by the energized condition of relay 152; The energized condition of relay132 maintains open the circuit of lamps S and 9. The energized condition, of relay 137 holdsopen the circuits of lamps 6 and 7, while theenergized condition of relay 144 holds open the circuitof lamp 0.

In the units group, the circuits of all lamps, excepting lamp 3, are maintained opened as follows: The energized condition of relay 154 holds open thecircuits of lamps 6,7, 2and 1; the energized condition of relay 150 holds Open the circuits of lamps 4 and 9;' the denergized condition of relay 159 holds open thecircuits of lamps 5 and '0; while the deenergized condition of relay 160 holds open the circuit of lamp 8 at this time. )The setting up of-any desired number may be traced in the above manner by determining the character of the impulses sent and noting which relays are actuated in the successive positions of Wipers 128, 129 and 130. In Fig. 5 is' shown'a table indicating the character of the impulses required to set up any desired number.

When the operator at O observes the lighting of the number indicating lamps, she releases key K and inserts plug 107 into a jack 161 in which the wanted line terminates.

When key K is released, relay 139 is deenergized. and a circuit is completed from grounded battery, winding of stepping magnet 126, its armature and back contact, offnormal contact' 149, armature and back contact of relay 139 to ground. Magnet 126 interrupts its own circuit to step the switch around to normal, at which time contact 149 is opened and the wipers are brought to rest on their first contacts. The opening of key contacts 135 also opens the locking circuit of such relays of the controlling combination as have been energized.

When the cord finder sequenceswitch'arrived inposition 19 a circuit was completed. from ground," cord finder sequence switch contact 162,- brush 163,terminal 164, conductor 165, connecting cord sequence switch con-. tact 166, and the winding of power magnet 30 to grounded battery, for movin the c0n+:' necting cord sequence switch out o osition lliand into position 16, at which time the'.

talking'conductors 167 and 168 are extended.

to thetru-nk conductors through connecting cord sequence switch contacts 169 and 170.

When the connecting cord sequence switch leaves position 11, the locking circuit of relay 48 is broken at connecting cordsequence switchcontact 62, and this relay deenergizes, completing a circuit at its right-hand armature and back contactfrom-ground, through cord finder sequence switch contact 171,- ;and winding of power magnet 36, for'moving-the cordfinder sequence switch from position 19 to position 20-. i I

In position 20 o-fthe cord finder sequence switch, a circuit .is completed for clown-drive magnet 172 from grounded battery, winding of magnet172, finder sequence switch contact 173 to ground. The brush set 44 is then returned to-normal under the control of a constantly rotating: roller 17 1. VVhen brush i1 engages commutator segment 40, a circuit is completed-from ground, finder sequence switch contact 175, brush 41, segment 40, cord finder sequence switch contact 176, winding of power 'magnet. 36 to grounded battery, for moving the cord finder sequence switch'out of position 20 and into position 1.

-VVhen: theoperator at, O inserted plug 107 intojack 161,.assuming that the line was idle,-a circuit was completed for relay 105 from grounded battery-,lamp 103, relay 105, sleeveof plug 107 sleeve contact of jack 161, and windingof cut ofi" relay 177 to ground. Relays 105 and-177 are'energized, relay 1-77 removing the control ofhis line signal from the called subscriber inthe well-known manner. [Relay 105 at. itsupper armature and front contact connects the upper talking conductor the connecting cord to the tip conductor of plug-107, I At its lower armature and frontcontact, relay 105 completes a,lo ckinghcircuit for-itself from grounded battery, shunting resistance 178, lower armatureof; relay :105, armature and front contact of relay 100, winding of relay 105. sleeve of plug 107, sleeve contact of jack 161, and winding of cut-off relay 177 to ground. The comparatively low resistance 178 shunts out lamp 103. Relay 100 is held energized at this time over a path from grounded battery, winding or relay 100, upper left-hand winding of repeating coil 99, contact 98 of key K, trunkconductor 97, terminal 96, brush 95, connecting-cord sequence switch contact 169, conductor 167 and the upper right-hand winding of repeating coil 179 to ground.

v The insertion ofplug 107 into jack 161 completed aci-rcuit for a supervisory relay 180 gover the called subscribers line in the usual mannera The operation of relay 180 completed a circuit for a supervisory relay 181 over a circuit'from grounded battery, lower right-hand winding of repeating coil 17 9, winding of supervisoryrelay 181, conductor168, connecting cord sequence switch contact 17 0,- brush 120, terminal 121, contact menace 182 of key K, lower left-hand winding of repeating coil 99, impedance coil 183, to ground at the armature and front contactof relay 180. The-connection is now complete and the subscribers-may converse. At the conclusion of the conversation, after both parties have replzicedtheir-re- Ceivers, the relay 180 will be deenergi'zed', due to the hanging up of the receiver by the called party. -This deenergization of relay 180 results in the deenergiz'ation ofsuipeu'v visory relay 181. The hanging up of-the calling partys receiver results in the deenergization of supervisory relay 184. The lighting of the wellknown supervisory lamps (not shown) at the ,operators position indicated at O inform that operator that connection is no longer desired, and she removes plug 14 from jack 15, whereupon relay 17 is deenergized. The denergization of relay l7'completes a circuitfrom ground, armature and back contact of relay 17, listening-key sequence switch contact 185, and the winding of power magnet 19 to, grounded battery, for moving the listeningkey sequence switch out of position 11 into position 1. v

In position 1 of the listening-key sequence switch, a circuit is completed from ground, armature and back contact of relay 17, listening key sequenceswitch contact 186, connecting cord sequence switch contact 187, winding of power magnet30 to grounded battery, for moving the connecting cord sequence switch out of position 16' and into position 18. a 'In position18 of the connecting cord sequence switch, a circuit is completed from grounded battery. winding ofapower magnet 188, connecting cord sequence switch contact 189 to ground. The brush set 79 is returned to normal position under the con; trol of a. constantly rotating roller 190. When brush 88 engages segment 191,a circuit is completed from ground, brush 88, segment 191, conductor 19,2, connecting .cord sequence switch contact 193, the winding of power magnet30 to grounded battery, forv moving the connecting cord sequence switch out ofposition l8 and into position 1. As soon as brushs'et 79 moved off the terminals of the trunk over which the connection was established, the circuit ofrelay 100 is broken and the shunt circuit about lamp 103 is removed, The resultant lighting of lamp 103 informs the operator at O that connection is no longer desired and sheremoves. plug 107 from jack 161. The apparatus has now all been restored to normal and is ready for reoperation. V q q Referring now to that point of the operation at which the operator at O inserted plug 107 into jack 161, it will be noted that if the called line is busy, the operator will receive a click in her telephone set indicated tors position,

at 19 1, due to the presence of potential on the sleeve conductor of jack 161. This potential "will be supplied from grounded battery, either through lamp 103 or through resistance 178, and when the tip of plug 107 engages the sleeve conductor of jack 161, a circuit will be completed from grounded battery, tip of plug 107, upper armature and back contact of relay 105, primary winding of coil 195 to ground, thus causing a click in the operators head set to notify her that the desired line is busy.

What is claimed is:

' 1. In a inulti-ofiice telephone exchange system, calling and called lines, a final connecting operators position, a trunk line, means including said trunk line for extending a calling line to said position, means for automatically indicating the number of a called line at said station, a combination of fast and slow-acting relays at said station to control said indicating means, and means for sending impulses of varying lengths over said trunk to control said relay combination.

2. In a multi-oi'lice telephone exchange system, calling and called lines, a final con necting operators position, a trunk line, means including said trunk line for extending a calling line to said position, means for automatically indicating the number of a called line at said position, a combination of fast and slow-acting relays at said position to control said indicating means, and means for sending impulses of varying lengths over both sides of said trunk simultaneously to control said relay combination.

3. In a multi-oflice telephone exchange system, calling and called lines, an A operaa B operators position, a trunk line. means including said trunk line for extending a calling line from said A operators position to said B operators position, means for visually displaying the number of a called line at said B operators position, a step-by-step switch operated over one side of said line, a combination of fast and slow-acting relays operated over said trunk conductors simultaneously, a second combination of relays operated over wipers of said switch and controlled by the relays of said first combination. said second combination of relays controlling said number displaying means, and means for sending impulses over both sides of said trunk simultaneously.

4. In a system employing electrical switching devices, an automatic switch, a power magnet therefor, a relay, an energizing cir- Gopies of this patent may be obtained for five cents each. by addressing the cuit for said magnet, a holding circuit for said magnet extending from contacts of said relay, and means to minimize sparking when said holding circuit is broken at said relay contacts.

5. Inasystem employing electrical switching devices, an automatic switch, a pOWer magnet therefor, an energizing circuit for said magnet, means connected'into the circuit of the operating magnet after the switch moves from normal to allow said magnet to release quickly, and means to minimize sparking when the circuit of said magnet is broken.

6. In a system employing electrical switching devices','an automatic switch. a power magnet therefor, a relay, normally closed contacts controlled by said switch, an energizing circuit for said magnet extending through said normally closed contacts, a holding circuit for said magnet extending through contacts of said relay, and means to minimizesparking when said holding circuit is broken at said relay contacts.

7. In a system employing electrical switching devices, an automatic switch, a power magnet therefor, normally closed contacts controlledby said switch, an energizing circuit for said magnet extending through said normally closed contacts, a high resistance circuit bridged across said normally closed contacts, a holding circuit for said magnet extending through said bridging circuit upon the actuation of contacts by movement of said switch, and means to minimize sparking when said holding circuit is broken.

8. In a system employing electrical switching devices, an automatic switch. a power magnet therefor, a relay, normally closed contacts controlled by said switch, an energizing circuit for said magnet extending through said normally closed contacts and contacts of said relay, a high resistance circuit bridged across said normally closed contacts, a holding circuit for said magnet extending through said bridging circuit and contacts of said relay, and a condenser shunted across the windings of said power magnet to minimize sparking when said holding circuit is broken at said relay contacts.

In witness whereof, I hereunto subscribe my name this 19th day of September, A. D. 1916.

ALBEN E. LUNDELL.

Commissioner of Patent:

Washington, D. 0."

said normally closed'

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