US1990438A

US1990438A - Telephone system

Info

Publication number: US1990438A
Application number: US687872A
Authority: US
Inventors: Moody Dwight Lyman; Newby Neal Dow
Original assignee: American Telephone and Telegraph Co Inc
Current assignee: AT&T Corp
Priority date: 1933-09-01
Filing date: 1933-09-01
Publication date: 1935-02-05
Anticipated expiration: 1952-02-05

Description

Feb. 5, 1935. b Y E AL 7 1,990,438

TELEPHONE SYSTEM Filed Sept. 1, 1933 5 Sheets-Shget 1 FIG 5 MARGIAML na. 3 E

Off/M725 T 0. L. MOODY MEMO/*5 N. 0. NEWBK ATTORNEY Feb. 5, 1935. D. L. MOODY ET AL 1,990,438-

TELEPHONE SYSTEM Filed Sept. 1, 1933 5 Sheets-Sheet 2 I I i H 0. L. M000) INVENTORS N NEWBV ATTORNEY Feb. s, 1935.

D. L. MOODY ET AL TELEPHONE SYSTEM Filed Sept. 1, 1933 5 Sheets-Sheet 3 INVEN7URS 0. .L. MOODY N. 0. NE W8) ATTORNEY Feb. 5, 1935. D. L. MOODY El AL 1,990,438

' TELEPHONE SYSTEM Filed Sept. 1, 1953 5 Sheets-Sheet 4 MMRG/NAL FIG. 4

' 0. LMOODV INVENTORS. N a NEWB}, B)

6 ATTORNEY Feb. 5, 19 35. D. L.YMOODY ET AL 1,990,438

TELEPHONE SYSTEM Filed Sept. 1, 1933 5 Sheets Shee t 5 INVENTORS D. L. MOODY N. 0. NE WE) (v 3% ATTORNEY Patented Feb. 5, 1935 TELEPHONE SYSTEM Application September 1, 1933, Serial No. 687,872

12 Claims. (o1. 179-27) This invention relates to telephone exchange systems and more particularly to trunking circuits for extending connections from calling lines in ofiices employing dial switching apparatus to operators positions.

The objects of the invention are to simplify trunks for trunking calls to an operators position and to distribute incoming calls to operators positions insuch a manner that the work of operators is lessened and the speed with which connections are established is materially increased.

Heretofore it has been the practice, for example, in trunking calls from a dial switching ofiice to a toll operators position to provide a group of trunks terminating in a terminal bank of a selector switch in the dial switching ofiice and terminating at the toll switchboard in jacks to which the toll operator has access, each trimk being provided at the toll switchboard with a calling lamp. To establish a call for toll service the calling subscriber dials a number, thus setting the selector to select the group of trunks extending to the toll switchboard. The selector then hunts and seizes an idle trunk, the trunk seized being indicated to the toll operator by the lighting of the calling lamp of such trunk. The toll operator to answer the call then plugs an idle cord circuit of her position into the jack of the calling trunk.

In accordance with the presentv invention, however, it is proposed to terminate all trunks extending from the banks of selector switches of an originating oilice having access thereto in the banks of a plurality of trunk finders located at the toll switchboard. Each trunkfinder is connected to multiple answering jacks appearing before the positions of operators at the toll switchboard who are assigned to handle calls from the local ofiice. Each trunk is provided at its incoming end with a line relay which operates when the trunk is seized at the local office to prepare a start circuit for an idle one of the trunk finders. Each trunk finder is normally rendered busy to incoming trunks until such time as a toll operator has connected an idle cord circuit with the jack associated therewith. When an operator becomes free to answer a call, she will plug an idle cord circuit into the jack associated with an idle trunk finder thereby rendering it capable of being started so that if a trunk has been Seized or is thereafter seized at the local ofiice such trunk finder will be started to hunt for the calling trunk and tocomplete a connection from a local cities to the cord circuit which has been In the event that more than one of the trunk 5 finders are idle and have operators cord circuits connected therewith, the seizure of a trunk will cause that one of the idle trunk finders to be started in which the calling trunk terminates in a lower level inorder that the huntingtime may be reduced to a minimum.

For a clearer understanding of the invention reference may be had to the accompanying drawings taken in connection with the following detailed description. Referring to the drawings:

Figure 11 shows schematically a calling subscribers line and brushes of a line finderhaving access thereto, and a first selector switch for extending a connection from the calling line to the local oflice end of a toll trunk shown in the right portion of the figure;

Fig. 2 shows the distant end of the trunk of Fig. 1, a trunk finder having access thereto and one end of a trunk local-tothe toll switchboard terminating in the brushes-ofthe trunk finder;

Fig. 3 shows the other end of the local trunk terminating in jacksappearing before the toll operators position; I r

Fig. .4 shows a cord circuit of a toll operators position having access to the trunk jacks of Fig. 3 together with control relays and keys of the operators position;

Fig. 5 shows the telephone set of the operators position; and

Fig. 6 is a. diagram showing how the figures of the drawings should be arranged fora complete disclosure, of the invention.

The line finder schematically indicated'at 101v may be of the well-known step-by-steptype similar to that shown, for example, in Patent No. 1,711,682 granted May 7, 1929 to H. Hovland and similar in most respects to the trunk finder shown more in detail in Fig. 2. Thefirst selector 102 is of the well-known Strowger type having a step-by-step vertical movement directed by the calling dial of a calling line to select a desiredtrunk group and a step-by-step rotary hunting movement to select an idle trunk in the selected group of trunks.

It will be assumed that the calling subscriber at substation 100 desires a toll connection and to initiate the call removes his receiver from the switchhook. In response to the initiation of thecall, the line finder 101 is started to find the.call-. ing line terminals whereupon a circuit is established from battery, left winding of relay 103 of selector switch 102, inner upper back contact of relay 104, brush 105 of line finder 101, thence over the calling line loop returning over brush 106 of line finder 101, upper back contact of relay 104, right winding of relay 103, upper normal contacts of the eleventh rotary step springs 107 to ground through the right winding of dial tone coil 108. Relay 103 operates over this circuit and a dial tone is also transmitted to the calling substation indicating to the calling subscriber that his line has been connected to the first selector switch 102 and that he may therefore commence dialing. Relay 103 upon operating closes an operating circuit for slow-to-release relay 109 extending from battery, winding of relay 109, front contact of relay 103 to ground at the lower back contact of relay 104,

In response to the operation of the subscribers dial relay 103 follows the dial impulses and upon its first deenergization closes a stepping circuit extending from ground at the lower back contact of relay 104, back contact of relay 103, right front contact of relay 109, winding of slow-to-re lease relay 110 to battery through the winding of the vertical stepping magnet 111. Relay 110 and magnet 111 operate, magnet 111 stepping the switch shaft one step vertically whereupon the vertical off-normal springs 112 close and the circuit of relay 113 is established from battery, winding of relay 113, lower contacts of off-normal springs 112, alternate contacts of relay 110 to ground at the left contacts of relay 109. Upon the next energization of relay 103 the circuit through the winding of relay 110 and winding of magnet 111 is opened and magnet 111 releases, but relay 110 being slow to release maintainsthe circuit of relay 113. It being assumed that the calling subscriber dials zero, the magnet 111 is intermittently operated through the successive deenergizations and energizations of relay 103 to step the selector switch shaft to'position the shaft brushes opposite the tenth bank level, When the dial returns to normal, relay 103 remains steadily energized thereby holding the circuit traced through the windings of relay 110 and magnet 111 open for a sufficient time to permit relay 110 to release, relay 113 being, now held operated in a circuit extending from battery through its winding, the lower contacts of offnormal springs 112, the back contacts of rotary magnet 114, the outer contacts of relay 113 to ground at the lower back contact of relay 104- preparatory to initiating the rotary hunting movement of the selector switch.

With relay 113 operated and relay 110 released, a circuit is established for the rotary magnet 114 extending. from battery through the winding of magnet 114, inner contacts of relay 113, normal contacts of relay .110 to ground at the left contacts of relay 109. Magnet 114 operates stepping the brushes one step in a rotary direction into engagement with the first set of terminals of the tenth bank level and opening the circuit of relay 113 which now releases in turn opening the circuit. of magnet 114. It will be assumed that the trunk which is connected to the first terminal set ofthe tenth bank level is busy and that ground is therefore connected to the test terminal 115 .thereof. When, therefore, the brushes of the selector switch engage the first terminal set a circuit is established from ground, front contacts of a relay of the trunk corresponding to relay 116, terminal 115, sleeve brush 117, iiiner lower back contact of relay 104, back contact of rotary magnet 114, lower contacts of off-normal springs 112, winding of relay 113 to battery. A branch of this circuit extends from brush 117 over the inner lower back contact and winding of relay 104, lower normal contacts of springs 107 to ground at the left contacts of relay 109, but relay 104 being shunted by ground encountered by brush 117 does not operate.

Relay 113 operates and'closes a holding circuit for itself from battery through its winding, thence as just traced over the back contact of magnet 114, the outer contacts of relay 113 to ground at the lower back contact of relay 104 and closes a circuit for operating the rotary magnet 114 which may be traced from battery, winding ofmagnet 114, inner contacts of relay 113, normal contacts of relay 110 to ground at the left contacts of relay 109. Magnet 114 energizes stepping the brushes of the selector switch to the next set of terminals in its tenth bank level and opening the circuit of relay 113 which thereupon releases opening the circuit of magnet 114. If the sleeve brush 117 now engages the test terminal of a trunk which also tests busy, relay 113 will reoperate and cause "magnet 114 to step the brushes another step. This action will continue until the test brush 117 encounters a sleeve terminal which is ungrounded when relay 104 no longer being shunted will operate in a circuit extending from battery, winding of relay 113,

lower contacts of off-normal springs 112, back contact of magnet 114, winding of relay 104, lower normal contacts of springs 107 to ground at the left contacts of relay 109. Due to the resistance of the winding of relay 104,. relay 113 does not operate in this circuit. Relay 104 upon operating disconnects the windings of relay 103 from the calling line whereupon relay 103 releases in turn releasing relay 109. It will be assumed that trunk 150 is idle and that the selector 102 seizes this trunk.

With relay 104 operated a circuit is now established from battery, lower winding of trunk relay 118, lower left winding of repeating coil 119, lower back contact of relay 120, ring terminal 121 and brush 122, inner upper frontcontact of relay 104, line finder brush 105, over the calling line loop, line finder brush 106, upper front contact of relay 104, tip brush 123 and terminal 124, upper back contact of relay 120, upper left winding of repeating coil 119 to ground through the upper winding of relay 118. Relay 118 operates closing an obvious circuit for relay 125. Relay 125 upon operating closes an obvious operating circuit for slow-to-release relay 116, a circuit extending from ground at its outer right front contact over the back contact of relay 126, resistance 127 to battery through the winding of relay 128 and in parallel therewith to battery through the winding of relay 129 and connects ground to sleeve terminal 130 for marking the trunk busy to other selector switches. Ground on terminal 130 is extended over sleeve wiper 117, lower front contact of relay 104, lower normal contacts of spring 107, winding of relay 104, back contact of magnet 114, lower contacts of off-normal springs 112 to battery through the winding of relay 113 for holding relay 104 operated and is extended to conductor 133 for holding the line finder, replacing ground which is removed at the left contacts of relay 109 after relay 109 releases. Relays 116. 128 and 129 operate, relay 116 con necting holding ground to the sleeve terminal 130 and to the windings of relays 128 and 129. Relay 128 performs no useful function at this time and relay 129 establishes a ringing tone circuitextending from the source of ringing cur rent 131, inner upper front contact of relay 129, left back contact of relay 132, lower back contact of relay 120, thence as traced over the subscribers line loop returning over the upper back contact of relay 120, upper left winding of repeating coil 119 to ground through the upper winding of relay 118. This ringing tone persists until the calling line has been extended to a toll operators cord circuit.

Relay 129 also establishes a circuit from battery, left winding of relay 134, left front contact of relay 125, lower contact of relay 129, lower right Winding of repeating coil 119, trunk conductor, 135, outer back contact of cut-off relay 201, winding of relay 202, inner back contact of relay 201, trunk conductor 136, upper right winding of repeating coil 119, upper contact of relay 129, inner right front contact of relay 125 to ground through the right winding of relay 134. Relay 202 operates in this circuit, but due to the resistance of its winding insufiicient current flows to cause theoperation of relay 134. Relay 202 upon operating connects the winding of cut-ofi relay 201 to the multiples of sleeve terminal 203 of the toll trunk appearing in the banks of all trunk finders such as finder 200 having access thereto and closes a circuit for operating the group relay 204. Relay 204 upon operating connects ground to the group segment 205 of vertical commutator 206 cf the trunk finder 200 corresponding to the bank level of the trunk finder in which the calling toll trunk appears and in multiple to group terminals of other trunk finders corresponding to the bank levels of such finders in which the trunk appears and prepares a start circuit for starting one of the trunk finders. No trunk finder will be started, however, unless a toll operator has plugged a cord circuit into the jack of the local trunk which is individual to a trunk finder.

It will first be assume that all toll operators of the team of operators are busy and that therefore all local trunks such as that shown in Fig. 3 are either busy on previously established toll connections, or if not in use on toll connections have no cord circuits of idle operators connected thereto. If a local trunk, for example, the trunk shown in Fig. 3 is idle. but has not been taken for use by a toll operator, relays 300 and 301 thereof will both be decnergized and therefore a circuit will exist from ground over the lower back contacts of these relays, conductor 302, normal contacts of the vertical off-normal springs 207 of trunk finder 200 in which the trunk terminates. upper back contact of relay 208 to battery through the lower winding of relay 209. Relay 209 will therefore be operated extending the start circuit from the left contacts of all group relays such as relay 204 to the next trunk finder of the group. If, as assumed, all other local trunks are either busy or are normally marked busy because no toll operator is free and no toll cord circuits have been connected therewith the relays corresponding to relay 209 of all trunk finders in which such local trunks terminate will also be operated in the manner just described and therefore the operation of a group relay 204 in response to an initiated toll call will be ineifective to start any trunk finder.

It will now be assumed that the operator whose cord circuit is shown in 4 is free to accept a toll call and connects the plug 400 of her cord circuit with the jack 303 of the local trunk. A

402 and lamp 401.

circuit is thereupon established from ground, back contact of polarized relay 304, lower low resistancewinding of sleeve relay 305, sleeves of jack 303 and plug 400, right normal contacts of relay 403 to battery in parallel through resistance Relay 305 operates and lamp 401 lights. Relay 305 closes. an obvious operating circuit for relay 301 and opens one point in the circuit of

trunk lamps

306, and 306, etc. Belay 301 upon operating closes an obvious circuit for relay 307 which upon operating bridges the condenser 308 between the inner terminals of the left windings of repeating coil 309 to prepare the talking circuit over the local trunk, short-circuits the lower high resistance of polarized relay 304 and closes the circuit of lamp 310 at the service observing operators position which may be traced from ground through lamp 310, outer left contacts of relay 307 to battery at the inner back contact of relay 300. front contact relay 301 prepares a circuit for trunk lamps 306, 300, etc., and its lower back contact removes ground from conductor 302. It will also be assumed that at this time there is no call waiting on any of the groups of toll trunks to which the trunk finder 200 has first choice access and that relay 204 is not therefore operated. When. therefore. ground is removed from conductor 302 relay 209 releases.

When thereafter, as previously described, relay 204 operates in response to the seizure of the toll trunk 150 by the operation of selector switch 102, a start circuit is established for the trunk finder 200 which may be traced from ground at the left contacts of relay 204, inner upper back contact of relay 209, winding of relay 208 to battery. Relay 208 upon operating connects ground to conductor 302, opens at its upper back contact one point in the circuit of release magnet 210 and closes the circuit of the stepping relay 211 which may be traced from ground at the lower front contact of relay 208, back contacts of the vertical stepping magnet 212 and rotary stepping magnet 213 upper winding of relay 211 to battery at the upper back contact of relay 209. Relay 211 operates closing a circuit from battery, upper back contact of relay 209. winding of vertical stepping magnet 212, lower back contact of relay 214, front contact of relay 211 to ground at the lower front contact of relay208. Magnet 212 operatesstepping the brush shaft of the trunk finder 200 one step vertically and opening at its back contact the circuit of relay 211 which thereupon deenergizes in turn opening the circuit of magnet 212 which also deenergizes. Mag- 5 net 212 upon deenergizing reestablishes the circuit of relay 211 which reoperates to reoperate magnet 212 to step the brush shaft a second step vertically.

This group hunting movement of the trunk finder continues until the vertical commutator brush 215 engages a segment of the vertical commutator 206 which has been grounded through the operation of a group relay 204, one of which is provided for each subgroup of twenty toll trunks appearing in the banks of the trunk finder. Since relay 204 is operated indicating that a call is waiting in the subgroup of trunks appearing in the second bank level of the lower brush bank of the trunk finder 200, when the commutator brush 215 engages segment 205 after the brush shaft has been stepped two steps v-er-- tically by magnet 212, acircuit is established from ground, right contacts of relay 204, segment 205,

brush 215, upper winding of relay 214, back At its inner lower contact of magnet'213, upperwinding of relay 211 to battery at the upper back contact of relay 209. Relay 211 is held operated over this circuit to prevent further operation of vertical magnet 212. Relay 214 upon operating opens a second point in the circuit of release magnet,

' brush shaft one step in a rotary hunting movement and opens the initial operating circuit traced through the upper winding of relay 214 and the upper winding of relay 211 whereupon relay 211 releases opening the circuit of magnet 213, but relay 214 remains operated over its locking circuit. Relay 211 upon releasing opens the circuit of rotary magnet 213 which releases again closing the previously traced circuit through the upper windings of relays 214 and 211, relay 211 upon reoperating again closing the circuit of magnet 213 to step the brush shaft a second step in a rotary direction. This action continues until one of the test brushes 216 or 21"! engages a sleeve terminal of a calling trunk, or in the case assumed, until brush 216 engages sleeve terminal 203 of the toll trunk 150. A circuit is thereupon established from battery, winding of cutoff relay 201, right front contact of relay 202, terminal 203, brush 216, lower winding of relay 218, lower back contact of relay 209, lower winding of relay 211 to ground at the inner lower front contact of relay 208. Relay 211 is held operated over this circuit to prevent further rotary stepping and relay 218 energizes sufficiently to close its inner upper front contact whereupon a circuit is closed from battery, upper winding and inner upper front contact of relay 218, front contact of magnet 213, front contact of relay 211 to ground at the lower front contact of relay 208. Relay 218 now fully operates opening at its inner lower back contact the initial operating circuit of relay 219, opening another point in the circuit of release magnet 210, closing a circuit for operating relay 209 extending from battery, lower winding of relay 209, intermediate upper front contact of relay 213 to ground at the lower alternate contacts of vertical off-normal springs 207, extending conductor 136 of the toll trunk 150 over terminal 220, brush 221, upper back contact of relay 219, upper front contact of relay 218 to conductor 222 of local trunk 3550 and extending conductor of the toll trunk over terminal 223, brush 224, lower back contact of relay 219, lower front contact of relay 218 to conductor 225 of local trunk 350.

Relay 201 which operated at the time brush 216 encountered terminal 203 disconnects the winding of relay 202 from the trunk conductors 135 and 136 whereupon relay 202 releases in turn opening the circuit of group relay 204. If no other toll trunk of the same subgroup is calling at this time relay 204 releases in turn releasing slow-to-release relay 208. Relay 209 upon operating extends a circuit from battery, through the winding and front contact of relay 201, terminal 203, brush 216, inner lower front contact of relay 218, inner lower normal contacts of relay 219, lower front contact of relay 209 to ground at the inner lower front contact of relay 208 until relay 208 releases and thereafter over conductor 302 to ground at the front contact of relay 300 of local trunk 350 as will be presently described. Relay 209 also extends ground from conductor 302 over its inner lower front contact through the inner upper front contact and winding of relay 218 to battery for holding relay 218 operated and at its upper back contact removes battery from the upper winding of relay 211, the lower winding of relay 214 and the winding of vertical magnet 212 thus releasing relay 214, and releases relay 211 by short-circuiting its lower winding over the lower front contact of relay 209. Relay 209 also at its inner upper transfer contacts transfers the start conductor extending from the front contacts of group relays such as 204, from the winding of relay 208 to the out start conductor 226 which extends in the usual manner to the next trunk finder of the groupof finders which have access to the toll trunks.

Upon the extension of trunk conductor 136 to trunk conductor 222 and trunk conductor 135 to trunk conductor 225 following the operation of relay 218, a circuit is established from battery, left Winding of relay 134, left front contact of relay 125, lower front contact of relay 129, lower right winding of repeating coil 119, conductor 135, terminal 223, brush 224, lower back contact of relay 219, lower front contact of relay 218, conductor 22.5, lower normal contacts of relay 311, lower left winding of repeating coil 309, inner left contact of relay 307, upper low resistance winding of polarized relay 304, upper left winding of repeating coil 309, upper normal contacts of relay 311, conductor 222, upper front contact of relay 218, upper back contact of relay 219, brush 221, terminal 220, conductor 136, upper right winding of repeating coil 119, upper front contact of relay 129, inner right front contact of relay 125 to ground through the right winding of relay 134.

Relays

134 and 304 both operate, relay 134 performing a function to be hereinafter described and relay 304 closing an obvious circuit for relay 300 which operates and looks over its upper front contact, the inner upper front contact of relay 301 strap 315 to ground at the upper front contact of relay 305. Relay 304 also disconnects ground at its back contact from the lower winding of relay 305 whereby the resistance of the sleeve of the cord circuit now extending to ground only through the upper high resistance winding of relay 305 is increased to such an extent that the cord lamp 301 becomes extinguished as a signal that a calling line has become extended to the operator's cord circuit.

Relay 300 upon operating opens at its inner lower back contact the previously traced circuit for lamp 310 which now becomes extinguished, and at its lower front contact connects ground over the lower front contact of relay 301 to conductor 302 to afford a holding ground for cut-off relay 201 and relay 218. This ground becomes connected before relay 208, which is slow to release, has time to release following the seizure of trunk 150 by the trunk finder.

Relay 134 upon operating closes a circuit from ground at its front contact through the right normal contacts and winding of relay 132 to battery. Relay 132 upon operating looks over its right alternate contacts to ground at the front contact of relay 116, discontinues the application of ringing tone from the source 131 to the calling line as a signal that the trunk has been extended to the operators cord circuit and at its left front contact connects condenser 137 between the inner right windings of repeating coil 119 to improve the talking circuit over trunk conductors 135 and 136 and bridges the alternating current relay 126 between the right winding of repeating coil 119. The talking circuit now extends inductively from the calling line to the left windings of repeating coil 309 of trunk 350 and this talking circuit is extended to the operators headset 501 as will be presently described.

Had the calling toll trunk terminated in the sec- 0nd level of the upper brush bank of trunk finder 200 rather than in the lower brush bank, as previously described, then when test brush 217 engaged the test terminal of the trunk battery thereon through the winding of the cut-off relay of the trunk would have been extended over brush 217, the lower winding of relay 219, the lower back contact of relay 218, the inner lower normal contacts of relay 219, lower winding of relay 211 to ground at the inner lower front contact of relay 208 causing relay 211 to be held operated as described and causing relay 219 to close its inner upper front contact. A circuit is thereupon established from battery, upper winding and inner up per front contact of relay 219, upper alternate contacts of relay 214, front contact of magnet 213, front contact of relay 211 to ground at the lower front contact of relay 208. Relay 219 now fully operates closing a circuit from battery through the upper winding of relay 218, intermediate upper front contact of relay 219, front contact of magnet 213, front contact of relay 211 to ground at the lower front contact of relay 208. Relay 218 operates performing the functions previously described except that with relay 219 operated the conductor 222 of trunk 350 is extended over the upper front contacts of relays 218 and 219 to brush 227 rather than to crush 221 and conductor 225 is extended over the lower front contacts of relays 218 and 219 to brush 228 rather than to brush 223. From this point the circuits function as previously described.

It will be recalled that upon the extension of the calling line by trunk finder 200 to trunk 350, relay 304 operated and extinguished the lamp 301 of the toll cord circuit. The operator seeing the lamp extinguished throws her talking key 404 to the right or talking position. A circuit is thereby closed from battery through the left windings of relays 405 and 403 in parallel, upper right alternate contacts of key 404 to ground at the normal contacts of relay 407. It is to be noted in this connection that all apparatus below the dot and dash line in Fig. 4 and all apparatus of Fig. 5 is positional apparatus common to all cord circuits of the operators position, one such cord circuit being disclosed in the upper portion of Fig. 4. Relay 403 upon operating transfers the circuit previously traced over the sleeve of plug 400 from battery through lamp 401 and resistance 402 in parallel to battery through the windings of marginal relay 409 and relay 410 in series. Relay 410 now operates in series with relay 305, but relay 409 does not. Relay 410 in turn closes an obvious circuit for operating relay 411. Lamp 401 and parallel resistance 402' are now connected into a circuit extending over the inner right front contact of relay 403 through high resistance 412 to ground at the left front contact of relay 411. Due to the high resistance 412, lamp 401 remains extinguished, At its inner left contacts relay 403 similarly transfers the sleeve conductor of plug 408 from connection with lamp'413 and resistance 414 to the windings of

relays

415 and 416 and transfers the circuit of lamp 413 in parallel with resistance 414 to the inner left contact of relay 417 through high resistanoe 418. With relays 405 and 403 operated a circuit is closed for operating

relays

407 and 419 which may be traced from battery, through the windings of these relays in parallel, outer left contacts of relays 403 and 405 to ground at the lower right alternate contacts of key 404. With relay 407 operated the initial operating circuit of relays 405 and 403 is opened and a holding circuit for them is closed through their right windings in parallel, the inner right front contact of relay 405 to ground at the alternate contacts of relay 407.

Relay 405 upon operating at its outer right and inner left contacts opens the talking conductors normally extending from the tip of plug 400 to the tip of plug 408 and from the ring of plug 400 to the ring of plug 408 and with relay 411 operated establishes a talking circuit which may be traced from the upper right winding of repeating coil 309, tips of jack 303 and plug 400, inner lower right normal contacts of ringing key 420, outer right alternate contacts of relay 405 upper rightnormal contacts of key 421, right front contact of relay 411, conductor 422, left windings of repeating coil 500, conductor 423, inner upper left normal and upper right normal contacts of key 424, lower inner right normal contacts of key 421, inner left alternate contacts of relay 405, rings of plug 400 and 'jack 303 to the lower right winding of repeating coil 309. With her headset 501 plugged up, the talking circuit just traced is inductively connected over the right winding of repeating coil 500. A talking circuit now extends inductively from the operators headset to the calling line and the operator is enabled to talk with the calling subscriber to receive information for completing the connection. The operator then proceeds to complete the connection in the well-known manner.

Should it be necessary for the operator to recall the calling subscriber, she may do so by operating the ringing key 420 to the right thereby establishing a circuit from battery, resistance 502, winding of relay 503, winding of relay 504, conductor 505, inner lower right alternate contacts of key 420, tips of plug 400 and jack 303, winding of ringback relay 311 to ground. Relays 503 and 504 and 311 operate, relay 503 closing a circuit from battery, winding of slow-'to-release relay 507, contact of relay 503, conductor 506, lower right contacts of key 420 to ground at the lower right alternate contacts of key 404. Relay 504 upon operating completes a circuit in multiple with the contacts of relay 507 for short-circuiting resistance 508 in the operators receiver circuit.

Relay 507 upon operating following the operation of relays 503 and 504 opens one short-circuiting path, but relay 504 being operated retains the other short circuiting path. When the key 420 is restored, relays 503, 504 and 507 release, relay 504 opening one short circuit around resistance 508 before relay 507 has time to release to restore the other short-circuiting path. Thus, during the releasing time of slow-to-release relay 507 the resistance 508 is included in the operators receiver circuit for a sufficient time to discharge the receiver before it is restored to normal efiiciency and thus to reduce the clicks incident to the operation of the ringing key 420.

Relay 311 upon operating transfers the talking

conductors

222 and 225 of trunk350 from the upper winding of relay 304 to the retard coil 312 thereby holding relay 134 of trunk 150 from releasing and causes relay 304 to'release. Relay 304 upon releasing connects the lower lowrre- 'sistance winding of sleeve relay 305 in parallel with the upper high resistance winding of relay 305 to the sleeve conductor of the cord circuit thereby decreasing the resistance to such an extent that marginal relay 409 at the operators position operates to connect low resistance 427 in parallel with high resistance 412 into the circuit of lamp 401. Lamp 401 now lights and remains lighted while ringing is in progress. Relay 311 also establishes a ringing circuit from the ringingsource 313 over its lower front contacts, conductor 225 thence as traced to conductor 135, the lowerright winding of repeating coil 119, lower front contact of relay 129, left front contact of relay 132, windings of alternatingcurrent relay 126, upper front contact ofrelay 1 29,-upper right winding of repeating coil 119, conductor 135 thence as traced to conductor 222, upper front contacts *of'relay 311 to ground.

Relay l26responds to the ringing current and opens at its back contact the circuit of slow-torelease relay 128 which, after an interval, releases and establishes a circuit extending from ground, windingof ringback relay 120, back contact of relay 128 to battery at the outer right front contact of relay 132. Relay l-20;operates, opening the operating circuit of relay 118 which releases in turn releasing relay 125. Relay 1% upon releasing opens one circuit for relay'1-1'6,;but since relay 134 is still held operated over the circuit extending through retard coil 312 of trunk 350, relay 116 is maintained operated ina circuit from battery through its winding, inner right front contact of relay 132 to ground at the front contact of -relay-134 and thus maintains relays 132 and 129 operated. Relay at its inner upper front contact connects holding ground to sleeve terminal 130 and to -the windings of relays 129 and-132 and atits outer front contacts establishes a ringing circuit-from ringing -gener ator 138 over the calling line loop to ground. After the calling subscriber responds, theoperator restores the ringing key 420'whereupon relays 503, 504, 507,311 and 126 release and relay 128 reoperates to-release relay 120. The source of ringing current l33-is now disconnected from the calling line. Relays 118,- 125 and. 304 now reoper ate restoring the connected trunk circuitsto the condition in which they were prior to the ringback operation. With relay 304 reoperated relay 409 releases and lamp 401 is again extinguished. p

Whenthe toll connection has been completely established and it is no longer necessary for the operator to listen in on the established connection, she restores the talking keyl04 whereupon relays 403, 405, 419 and 407 release and the talking circuit is established over the'talking conductors of the cord circuit from the tip-of plug 400 tothe tip ofplug 408 and from-the ring unplug 400 to the ring of plug 408. With relay-403 released the cord circuit lamps 401 and 413 are then reconnectedto the sleeve conductors of the cord circuit. V

I The toll connection fromthe calling line to the toll operators position may be arranged as desired for release under the-joint control of the calling subscriber and toll operator, or for release solely under the control of the operator. The release under j'o'int control will first be des'cribd, the straps 3 14 and 315 being connected as shown in Fig. 3. If upon the termination of conversation over the toll connection the operator withdraws plug 400 from jack 303 before the calling subscriber restores his receiver to the switchhook, relay 305releases, but since with the calling subscribers receiver on the switchhook relay 304 is maintained operated over the talking circuit extending to the trunk 150, relay 300 is maintained operated over the front contact of relay 304 and relay 301 is held operated in a circuit from battery, winding of relay 301, strap 315, inner upper front contact of relay 301, upper front contact of relay 300 to ground at the front contact of relay 304. Relay 301 in turn maintains relay 307 operated. Consequently, the

trunk lamps

306, 306, etc. become lighted in acircuit from battery, inner lower front contact of relay 301, back contact of relay 305, strap 314,

lamps

306, 306, etc. to ground as a signal that the calling subscribers line is still connected to the trunk 350. The toll operator who disconnectedorancther operator who has access to the trunks over other multiple jacks thereof such 'asjack 303' will answer the call by plugging up a toll cord circuit.

If the calling subscriber restores his receiver to the switchhook before the toll operator disconnects, relay118 will release in turn releasing relay 125 whereupon the direction of current iiowing over the trunk conductors 135 and 136 through the upper winding of polarized relay 304 will be reversed thereby releasing relay 304. The release of relay 304 will then cause the cord lamp 401 to light-asa disconnect signal. When thereby decreasing the current fiowin'gthrough the windingof marginal relay 134 of trunk to such an extent that relayfl'34 releases. Since relay-300 is slow to release, it remains operated for a short interval-after relay 301 releases and therefore groundis momentarily removed from conductor 302. Relay 218 now. releases, but relay 209 being held in the locking circuit extending through its lower winding, the upper back contact of relay'208 to ground at the lower alternate contacts of vertical off-normal springs 207 remains operated until the trunk finder 200 returns to normal. Relay-219 if operated is also held operated over its upper winding, its inner upper front contact, the upper normal contacts of relay 214 to ground at the off-normal springs 207 until the trunk finder returns to normal. With relay- 218 released a circuit is established from battery, winding of relea'semagnet 210, upper contacts-of off-normal springs 207, inner upper back contact of relay 214, upper back contact-of re1ay218, upper back contact of'relay 208 to ground at the lower alternate contacts of off-normal springs 207. Magnet-210 upon operating causes the restoration of the trunk'finder brush shaft to normal position whereupon the alternate contacts of off-normal springs 207 open to release-magnet 2'10 and to release'relay 209 if there is'no other call-awaiting completion in the group of trunks to which the line finder has access. --If there-is such'a call awaiting completion, a grouprelay such as 204 will be operated andwill maintain relay 209 lockedover its upper front contacts-and-w-inding. This is for the purpose of preventing the start circuit extended over the upper front contacts of relay 209 and out start conductor 226 to the start relay of the next trunk finder from being opened until such next trunk finder has been started.

With relay 134 of trunk 150 released, since relay 125 is at this time released, no circuit is effective for holding relay 116 operated and it now releases in turn releasing relays 129, 128 and 132 and removing holding ground from sleeve terminal 130. Ground is now removed from conductor 133 to initiate the release of line finder 101 and the holding ground for relay 104 is removed and relay 104 releases. A restoring circuit for selector switch 102 is now effective which may be traced from battery, winding of release magnet 139, upper contacts of cit-normal springs 112, back contacts of

relays

109 and 103 to ground at the lower back contact of relay 104. Magnet 139 causes the release of the brush shaft of selector switch 102 to normal in which position the contacts of elf-normal springs 112 open the circuit of magnet 139. At the trunk 350 as soon as relay 300 releases ground is reapplied over the lower back contacts of relays 300 and 301, conductor 302, normal contacts of off-normal spring 207, upper back contact of relay 208 to battery through the lower winding of relay 209 for holding relay 209 operated until a toll operator becomes free and plugs a toll cord circuit into a multiple jack of trunk 350. All apparatus used in the establishment of the toll connection has now been restored to normal condition.

When it is desired to place the release of an established toll connection entirely under the control of the toll operator, strap 314 of Fig. 3 is omitted and strap 315 is connected between the inner upper front contact of relay 301 and grounded conductor 316. When under these conditions the toll operator disconnects plug 400 from trunk jack 303 before the calling subscriber restores his receiver to the switchhook, the release of relay 305 in turn releases relay 301 since relay 301 is not now looked under the control of relays 300 and 304. The release of relay 301 new releases relay 307 and at its lower front contact disconnects ground from conductor 302 to initiate the release of the connection as previously described. When the connection between trunk 150 and trunk 350 is released, relay 304 releases in turn releasing relay 300 and with relays 300 and 301 both released, ground is reconnected to conductor 302 as previously described.

If the subscriber restores his receiver before the operator disconnects, relay 304 will release, but since relay 301 is held operated by relay 305 as long as the plug 400 is in jack 303, relay 300 will be held operated in a circuit from battery through its winding and upper front contact, the inner upper front contact of relay 301, strap 315 to grounded conductor 316. Since both relays 300 and 301 are operated, ground is maintained on conductor 302 and the release of the connection is not initiated. The release of relay 304 will cause the lighting of cord lamp 401 in the manner described as a disconnect signal. When in re sponse to the disconnect signal the operator withdraws plug 400 from jack 303, relay 305 will release in turn releasing relays 301, 300 and 307. Since relay 300 is slow to release, ground will momentarily be removed from conductor 302 by the release of relay 301 initiating the release of the connection. As soon as relay 300 completely releases, ground is then reapplied to conductor 302 until such-time as an operator becomes free and connects a cord circuit to a multiple jack of the trunk 350.

In order that the trunks, such as 350, of a group of trunks appearing before operators positions of a team of operators may, when idle, be taken for use in a definite order when operators become free, idle trunk lamps 317, 317, etc. are provided adjacent the

multiplejacks

303, 303, etc. of each trunk. The circuit of these lamps is extended over chain contacts controlled by the relay 301 of each trunk. Thus, for example, if the first trunks of the group are busy and consequently their relays corre-. sponding to relay 301 are operated and the trunk 350 is idle and relay 301 is not operated, the circuit of lamps 317, 317', etc. will be closed therethrough from ground over the upper backcontact of relay 301 and front contacts of relays corresponding to relay 301 of preceding trunks to battery and lamps 317, 317 etc. will light as an indication that that trunk 350 is available for use.

Similarly, when trunk 350 is taken for use and all preceding trunks are busy, the operation of relay 301 will extinguishlamps 317, 317', etc. and ex tend the chain circuit from battery over the upper front contact of relay 301 and the back contact of a relay corresponding to relay 301 of the succeeding trunk which is'available for use to light the idle indicating lamps thereof corresponding to lamps 317, 317 etc.

What is claimed is:

1. In a telephone exchange system a manual switchboard, operators positions atsaid switchboard, answering jacks on said switchboard, trunk finders associated respectively with said jacks, cord circuits at said operators positions for connection with said jacks, trunk circuits extending from an originating ofiice and terminating inthe banks of said trunk finders, means at the originating office for selecting an idle one of said trunk circuits, and means operable upon the seizure of one of said trunk circuits for starting an idle one of said trunk finders with which an operator has previously connected an idle cord circuit to hunt for said calling trunk circuit and to extend a connection from the originating office to the connected cord circuit.

2. In a telephone exchange system, a manual switchboard, operators positions at said switchboard, ans-wering jacks on said switchboard," trunk finders associated respectively with'said jacks, cord circuits at said operators positions for connection with said jacks, trunk circuits extend ing from an originating ofiice and terminating in the banks of said trunk finders, selector switches at the originating ofiice for selecting an idle one of said trunk circuits, and means operable upon the seizure of one of said trunk circuits for starting an idle one of said trunk finders with which an operator has previously connected an idle cord circuit, to hunt'for said calling trunk circuit and to extend a connection from the originating ofiice to the connected cord circuit.

3. In a telephone exchange system, a manual switchboard, operators positions at said switchboard, answering jacks on said switchboard, trunk finders associated respectively with said jacks, each trunk finder when not in use beingnormally rendered inoperable, cord circuits at said operators positions for connection with said jacks, the connection of a cord circuit with the jack associated with a trunk finder rendering said trunk finder operable, trunk circuits extending from an originating ofiice and terminating in the banks of said trunk finders, means at the originating office for selecting an idle one of said trunk cir-.

cults, and means operable upon the seizure of one of said trunk circuits for starting one of said trunk finders which has beenrendered operable by the previous association of a cord circuit therewith to hunt for said calling trunk circuit and to extend a connection from the originating office to the associated cord circuit.

4. In a telephone exchange system, a manual switchboard, operators positions at said switchboard, answering jacks on said switchboard, trunk finders associated respectively with said jacks, each trunk finder when not in use being normally rendered inoperable, cord circuits at said operators positions for connection with said jacks, the connection of a cord circuit with the jack associated with a trunk finder rendering said trunk finder operable, trunk circuits extending from an originating office and terminating in the banks of said trunk finders, means at the originating office for selecting an idle one of said trunk circuits, means operable upon the seizure of one of said trunk circuits for starting one of said trunk finders which has been rendered operable by the previous association of a cord circuit therewith to hunt for said calling trunk circuit and to extend a connection from the originating ofiice to the associated cord circuit, and means for rendering an operatedtrunk finder busy.

5. In a telephone exchange system, a manual switchboard, operators positions at said switchboard, answering jacks on said switchboard, trunk finders associated respectively with said jacks, each trunk finder when not in use being normally rendered inoperable, cord circuits at said operators positions for connection with said jacks, the connection of cord circuits with jacks associated with trunk finders rendering said trunk finders operable, trunk circuits extending :from an originating office and terminating in the banks of said trunk finders, .means at the originating office for selecting an idle one of said trunk circuits, and means operable upon the seizure of one of said trunk circuits'for starting that one of said trunk finders which have been rendered operable which has access to said calling trunk circuits with the shortest hunting movement to hunt for said calling trunk circuit-and to extend a connection from the originating ofiice to the associated cord circuit.

6. In a trunk telephone exchange system, a manual switchboard, operators positions at said switchboard, answering jacks on said switchboard, trunk finders associated respectively with said jacks, each trunk finder when not in use being normally rendered inoperable and having a multigroup terminal bank, cord circuits at said operators positions for connection with said jacks, the connection of cord circuits with the jacks associated with trunk finders rendering said trunk finders operable, trunk circuits extending from an originating ofiice and multiplied in the banks of said trunk finders, each trunk circuit being multipled to different bank groups of said trunk finders, means at said originating ofiice for selecting an idle one of said trunk circuits and means operable upon the seizure of one of said trunk circuits for starting that one of said trunk finders which has been rendered operable, which has access .to said calling trunk circuit with the shortest group hunting movement to hunt for said calling trunk circuit and to extend a connection from the originating office to the associated cord circuit.

'7. In a telephone exchange system; a manual switchboard, operators positions at said switchboard, answering jacks on said switchboard, trunk finders associated respectively with said jacks, cord circuits at said operators positions for connection with said jacksa relay in each trunk finder normally operated if said trunk finder is idleand no cord circuit is connected with the answering jack associated therewith for rendering said trunk finder unavailable for use, means responsive to the connection of cord circuits with the jacks of idle trunk finders for releasing the relays thereof to render said trunk finders available, trunk circuits extending from an originating office and terminating in the banks ofsaid trunk finders, and means at the originatingofiice for selecting an idle one of said trunk circuits for starting that one of said available trunk finders which has access to said trunk circuit with the shortest hunting movement to hunt forsaid trunk circuit and to extend a connection from the originating oflice to the associated cord cir cuit.

8. In a telephone exchange system, a manual switchboard, operators positions at said switchboard, answering jacks on said switchboard, trunk finders associated respectively with said jacks, cord circuits at said operators position for connection with said jacks, a relay in each trunk finder normally operated if said trunk finder is idle and no cord circuit is connected with the answering jack associated therewith for rendering said trunk finder unavailable for use, means responsive to the connection of cord circuits with the jacks of idle trunk finders for releasing the relays thereof to render said trunk finders available, trunk circuits extending from an originating office and terminatingin the banks of said trunk finders, means at the originating office for selecting an idle one of said trunk circuits for starting that one of said available trunk finders which has access to said trunk circuits with the shortest hunting movement to hunt for said trunk circuit and to extend a connection from the originating ofiice to the associated cord circuit, and means for reoperating the relay of the started trunk finder to render the next available trunk finder operable on the next call incoming over another trunk circuit.

9. In a telephone exchange system, a manual switchboard, operators positions at said switchboard, answering jacks on said switchboard, trunk finders associated respectively with said jacks, cord circuits at said operators positions for connection with said jacks, a relay in each trunk finder normally operated if said trunk finder is idle and no cord circuit is connected with the answering jack associated therewith for rendering said trunk finder unavailable for use, means responsive to the connection of a cord circuitwith the jack of an idle trunk finder for releasing the relay thereof to render said trunk finder available, trunk circuits extending from an originating office and terminating in the banks of said trunk finders, means at the originating office for selecting an idle one of saidtrunk circuits for starting the available trunk'finder to hunt for said trunk circuit and to extend a connection from the originating oiiice to the associated cord circuit, and means operable upon the disconnection of the cord circuit from the jack associated with said operated trunk finder for releasing said trunk finder and for operating said relay to again render said trunk finder unavailable for use.

10. In a telephone exchange system, a manual switchboard, operators positions at said switchboard, answering jacks on said switchboard, trunk finders associated respectively with said jacks, cord circuits at said operators positions for connection with said jacks, a relay in each trunk finder normally operated if said trunk finder is idle and no cord circuit is connected with the answering jack associated therewith for rendering said trunk finder unavailable for use, means responsive to the connection of a cord circuit with the jack of an idle trunk finder for releasing the relay thereof to render said trunk finder available, trunk circuits extending from an originating ofiice and terminating in the banks of said trunk finders, means at the originating ofiice for selecting an idle one of said trunk circuits for starting the available trunk finder to hunt for said trunk circuit and to extend a connection from the originating office to the associated cord circuit, and means jointly controlled from the originating ofice and by the disconnection of the cord circuit from the jack associated with said operated trunk finder for releasing said trunk finder and for operating said relay to again render said trunk finder unavailable for use.

11. In a telephone exchange system, a manual switchboard, operators positions at said switchboard, a local trunk circuit terminating at one end in answering jacks on said switchboard and at the other end in a trunk finder, a relay in said trunk finder, a quick-releasing relay and a slow releasing relay associated with said local trunk circuit, a circuit for said first relay normally closed over the back contacts of said trunk circuit relays for holding said first relay operated when said trunk finder is idle and no cord circuit is connected to said local trunk circuit for rendering said trunk finder unavailable for use, means responsive to the connection of a cord circuit with the local trunk circuit for operating one of said trunk circuit relays to release said first relay to render said trunk finder available, trunk circuits extending from an originating ofiice and terminating in the bank of said trunk finder, means at the originating mice for selecting an idle one of said latter trunk circuits for starting said trunk finder when available for use to hunt for said latter trunk circuit and to extend a connection from the originating ofice to the cord circuit associated with the local trunk circuit, means responsive to the extension of said connection for operating the other of said local trunk circuit relays, means responsive to the disconnection of the cord circuit from the local trunk circuit and disconnection at the originating office for releasing said trunk circuit relays, and means controlled by the release of said quick-releasing relay before the release of said slow-releasing relay for releasing said trunk finder, said relays when both released reoperating said trunk finder relay to again render said trunk finder unavailable for use.

12. In a telephone exchange system, a manual switchboard, operators positions at said switchboard, a local trunk circuit terminating at one end in answering jacks on said switchboard and at the other end in a trunk finder, a relay in said trunk finder, a pair of relays associated with said local trunk circuit, a circuit for said first relay normally closed over the back contacts of said trunk circuit relays for holding said first relay operated when said trunk finder is idle and no cord circuit is connected to said local trunk circuit for rendering said trunk finder unavailable for use, means responsive to the connection of a cord circuit with the local trunk circuit for operating one of said trunk circuit relays to release said first relay to render said trunk finder available, trunk circuits extending from an originating oifice and terminating in the bank of said trunk finder, means at the originating ofiice for selecting an idle one of said latter trunk circuits for starting said trunk finder when available for use to hunt for said latter trunk and to extend a connection from the originating ofiice to the cord circuit associated with the local trunk circuit, means responsive to the extension of said connection for operating the other of said trunk circuit relays, and means responsive solely to the disconnection of the cord circuit from the local trunk circuit for releasing one of said local trunk circuit relays to release said trunk finder, said other trunk circuit relay then releasing to reoperate said trunk finder relay to again render said trunk finder unavailable for use.

DWIGHT LYMAN MOODY. NEAL D. NEWBY.