US1829798A - Community dial switching telephone system - Google Patents

Description

Nov. 3, 1931. w. HATTON ET AL 1,829,798

COMMUNITY DIAL SWITCHING TELEPHONE SYSTEM Filed March 8, 1930 4 Sheets-Sheet 1 Q u |||||nn |n||||||| Q \Q\ g Q IIHI' INVENTORS w. HATTON C.DE VR/ENDT L EJROUSSEAU Nov. 3, 1931. w. HATTON ET AL 1,829,798

COMMUNITY DIAL SWITCHING TELEPHONE SYSTEM Filed March 8, 1930 4 Sheets$heet 2 ti 5 m 2% a E VMHATTONv C. DE VR/ENDT EJROUSSEAU A TTORNE Y Nov. 3, 1931. w. HATTON' ET AL COMMUNITY DIAL SWITCHING TELEPHONE SYSTEM 4 Sheets-Sheet 4 Filed March 8, 1930 /NVENTORS \MHATTON C.DE VR/ENDT E.d. ROUSSEAU BY ATTOR /MEY Patented tam PATENT OFFICE WILLIAM HATTON, CHARLES DE VRIENDT, AND ERNEST JEAN BOUSSEAU, OF PARIS, FRANCE, ASSIGNORS T0 WESTERN ELECTRIC COMPANY, INCORPORATED, 013' NEW YORK, N. Y., A CORPORATION OF NEW YORK COMMUNITY DIAL SWITCHING TELEPHONE SYSTEM Application filed March 8, 1930, Serial No. 434,215, and in Great Britain November I, 1929.

This invention relates to dial switching telephone exchange systems and more particularly to systems comprising small oflices known as satellite or community offices. The object of the invention is to so arrange the apparatus of such community offices that subscribers whose lines terminate therein may by dialing directory numbers having a uniform number of digits either have access to subscribers lines which terminate in other oflices of the exchange system or have access to subscribers? lines which terminate locally with equal facility and in the case of local calls without the assistance of apparatus not local to the community office in which the call originates.

In accordance with this invention two embodiments of which have been disclosed herein by way of example, a subscriber whose line terminates in the community office of the exchange area upon initiating a call at once obtains connection over an idle trunk outgoing from the ofiice. This trunk may extend to a tandem district ofiice or to a central ofiice of the exchange area. A typical exchange system of which the community oflice may form a part is disclosed in our copending application Serial No. 434,214, filed concurrently herewith. When the call so initiated has been thus extended, the calling subscriber receives the customary dial tone and then proceeds to dial the digits of the wanted line number. In all cases the subscriber dials a uniform number of digits, in the particular system illustrated five digits. The first three digits dialed determine the destinaton of the call, that is, whether the call is for another subscribers line terminating in the same community office or for a subscribers line terminating in some other office of the exchange system. If these digits indicate that the call is of a local character, then the outgoing trunk is released and the apparatus of the community ofiice is rendered efl'ect-ive to register the remaining two digits dialed and to control the setting of local selector switches to terminate the call.

More particularly, referring to the first embodiment of the invention, the community ofiice is designed to have access to from 100 to 300 lines, although it will be obvious that the principles of the invention are applicable to such ofi'ices havingaccess to a larger number of lines. The ofiice is provided with a plurality of link circuits, each such link terminating at one end in a line finder and at the other end in a plurality of branches each having a group selector. Thus, if the office is designed for access to 200 lines. each link will terminate in two group selectors and if access is desired to 300 lines, each link will terminate in three group selectors. Of the lines to which these group selectors have access, certain lines terminatin in one of the group selectors will be use for outgoing calls.

When a subscriber initiates a call by the removal of his receiver from the switchhook, all line finders of idle links having access to the calling line are started in search of.

the calling line and when one of the line finders finds the calling line, it is seized and the finders of other links are stopped. Thereupon, that one of the group selectors of the link taken for use which has access to outgoing trunks is started in search of an idle trunk. When an idle trunk becomes associated with the link circuit, a discriminating registering device which is common to the group of trunks is associated with the trunk taken for use in readiness for registering the first three digits to be dialed by the calling subscriber, and a dialing tone is transmitted to the calling line. The calling subscriber then proceeds to dial the first three digits of the wanted line number. If as will be assumed, these digits are indicative that the calling subscriber desires a connection with another subscribers line which terminates in the same ofiice, a discriminating signal is transmitted back to the link circuit and the registering device is released. This signal determines whether the wanted line may be reached over the terminal bank of the same group selector over which access was had to the outgoing trunk, or whether it may be reached over one of the other par allelly connected group selectors, and renders marking register switches effective in the link circuit for recording the remaining two di its of the line designation dialed by the calling subscriber. In accordance with the settings of the marking registers the group selector which has been made effective by the discriminating signal is thereupon operated to select the wanted line and to release the connection to the seized outgoing trunk.

The group selectors employed in connection with this embodiment-of the invention have been illustrated as single motion hunting type step-by-step switches, each having access to 100 sets of bank terminals. These selectors might, however, be of the wellknown clutch driven type.

Had the first three digits dialed indicated that the desired line terminates in some other oflice of the exchange, then when the calling subscriber dialed the last two digits, these digits would then have been transmitted out over the trunk line for the purpose of con trolling selector switches at another" oflice rather than recorded on registers of the link circuit. In this case the common discriminating registering device is effective to control apparatus in the trunk circuit for settin up a zone metering registration for metering the call in accordance with the destination thereof. This metering feature, however, forms no part of the present invention but has been made the subject matter of our 'copending application Serial No. 434,- 216, filed concurrently herein.

In the second embodiment of the invention the community oflice is designed to have access to a maximum of 100 lines and thus each link circuit is provided with two branches each terminating in a 50 oint stepby-step rotary group selector. If less than 50 lines terminate in the ofiice, but one of these group selectors is necessary. As in the modification previously described, the initiation of a call causes the seizure of the calling line over the line finder of an idle link circuit, the seizure of an idle outgoing trunk and the association therewith of a discriminating. registering device.

If the first three digits dialed indicate that the call is of a local character, a discriminating si nal is transmitted back to the link circuit in icative of that fact and the first of the two remaining digits dialed by the calling subscriber is then registered upon a marking register'in the link circuit. As soon as this register steps off normal, the group selector over which connection was made to the outgoing trunk is started to advance and if the marking register indicates that the wanted line is located in a tens group to which such group selector has access, the group selector will advance to such marked tens group. Thelast digit dialed. by the calling subscriber will then set that group selector in a units selection movement to the terminal of the wanted line. If, however, the community ofiice has more than 50 lines terminating therein and the link circuit also terminates in a further group selector and the tens di it recorded indicates that the wanted line is ocated in a tens group to which such other group selector has access,

hunting movement to the group marked by the marking register. The units digit dialed by the calling subscriber is then employed to set such group selector in a units selection movement upon the terminals of the wanted line.

Provision is also made for releasing an established connection to a called subscribers line through the o eration of a thermostatic relay if the calling subscriber fails to restore his receiver within a predetermined interval following the restoration of the called subscribers receiver.

Referring to the drawings, Fig. 1 shows at the left a subscribers line, one of the link circuits of the community oflice terminating at one end in a line finder and at the other end in a plurality of parallelly connected group selectors, tens and units marking switches for controlling the setting of the group selectors and at the right one outgoin trunk circuit and a subscribers line terminating in the bank of one of the group selectors.

Fig. 2 shows the apparatus associated with the outgoing end of the trunk circuit and in the lower right portion of the fi ure a message register impulsing switch or controlling the calling line message register of Fig. 1 in accordance with the zone of the exchange into which a connection is extended. Fig. 3 shows a discriminating registering device for recording and translating the first three digits dialed by a calling subscriber together with a trunk huntingswitch, shown in the upper portion of the figure, whereb the registering device may be associated with any one of -a group of trunk circuits.

ig. 4 shows a modification of the link circuit shown in Fig. 1.

For a com lete disclosure ofthe invention 2 shoul be placed at the right of Fig. 1

F1 and Fig. 3 should be placed beneath Fig. 2.

The invention when considered in connection with the modification shown in Fi 4 may be illustrated by placing Fig. 4 in pace of the link circuit shown in Fig. 1.

All of the switches disclosed are of the single motion step-by-step type. The finders and 400 of Figs. 1 and 4 are of the type having no normal position and each is equipped with two sets of wipers placed on the switch shaft 180 apart. The group selectors 110, 120 and 130 of Fig. 1 are of the same general type as the line finders and each has access to one hundred sets of bank terminals. The group selector 110 has access to a group of five outgoing trunks and to 90 subscribers lines and the other two group selectors 120, and 130, the wipers of selector 130, not being illustrated, each have access to one hundred subscribers lines. The marking switches 140, 150 and 430, the registers 310 and 320 and the message register impulsing switch 200 are all minor type switches. The translator switch 330 of Fig. 3 has access to fifty sets of bank terminals, the terminals of the upper four levels being cross-connected, as may be desired, to the cross-connecting frame 340 for controlling metering and the selection of a proper group switch of Fig. 1 for establishing local connections. The trunk hunting switch 300 which has no normal position has access to the group of trunk circuits, one of which is disclosed in Fig. 2. The group selector switches 410 and 420 of Fig. 4 are similar to the selector switches of Fig. 1, but have access respectively to but fifty sets of line terminals.

' For a better understanding of the invention reference may be had to the following 5 description in which the progress of a call from the calling line 101 over the circuits of Figs. 1 to 3 inclusive, will first be described in detail. \Vhen the calling subscriber removes his receiver from the switchhook a circuit is established from battery, through the winding 'of line relay 102, the upper back contact of cut-off relay 103, over the loop of the calling line to ground at the lower contact of relay 103. Relay 102.upon operating establishes an obvious circuit for the common group relay 104 which in turn establishes a circuit for the common line finder start relay 105. Relay 105 at its front contacts closes start circuits for the stepping magnets of all idle line finders having access to the group of lines in which the calling line is located. It will be assumed that the line finder 100 is that one of these line finders which is to be used in establishing the connection. The circuit for starting this line finder may be traced from battery, through the magnet winding and interrupter contacts of stepping magnet 106, contacts of relay 105, contacts of test jack 107, back contact of relay 108 to ground at the upper normal contacts of relay 109.

In response to the operation of magnet 106 the wipers of the line finder are advanced until the test wiper 111 engages the test terminal of the calling line. Then a circuit is established from ground, through the lower winding of relay 108, the normal contact of thermostatic relay 112, contacts of jack 107. wiper 111 to battery at the front contact of relay 102. Relay 108 upon energizing closes an obvious circuit for relay 113 and opens at its back contact the circuit of stepping magnet 106. \Vith relay 113 operated, ground is connected over the lower contact of relay 113 and the upper winding of relay 108 to .test wiper 111 to prevent the seizure of the is found, relay 117 operates in a circuit ex tending from ground at the upper normal contact of relay 118, wiper 119 of markin switch 140 and its normal terminal, strapped terminals with which wi-per 121 of the group selector engages, winding of relay 117, inner upper front contact of relay 113, wiper 122,

conductor 201 to battery through the winding of relay 202. Relay 202 also operates in this circuit and performs a function which will be described later.

Relay 117 upon operating, opens the circuit of magnet 114 to arrest the operation of the group selector 110 and establishes over its front contact and a contact of relay 113 a circuit for relay 123. At its inner lower front contact relay 123 applies direct ground through the winding of relay 117 over wiper 122 to conductor 201 to mark the selected trunk busy and closes an obvious circuit for relay 124. Relay 124 upon operating establishes a circuit from ground through the winding of relay 109, over wiper 125 of line finder 100 to battery through the calling line cut-off relay 103. Relay 103 disconnects the line relay 102 which in turn releases relay 108 and if there are at the time no other lines calling in the group, releases common relays 10. and 105 thereby arresting the operation of an other idle line finders that may have been started. After the release of relay 108, relay 113 is locked over its inner lower front contact, the back contact of relay 126 to ground at the upper front contact of relay 109.

Relay 202 of the link circuit which operated in series with test relay 117 upon operating establishes an obvious circuit for relay 203. With relay 109 operated a circuit is established from ground, through the upper winding of relay 204, wiper 127 ofselector 110, upper alternate contacts of relay 123, lower front contact of relay 109, wiper 128, over the calling line, back over wiper 129, the inner upper contact of relay 109, the inner upper front contact of relay 123, wiper 131 to battery through the lower winding of relay 204. Re ay 204 operates in this circuit and closes an obvious circuit for slow to release relay 205 which operates in turn and causes the operation of relay 206. An impulse repeating circuit is now extended over the outgoing conductors 207 and 208 of the trunk circuit for repeating impulses to the oflice to which the community oflice is subsidiary, this circuit extending from conductor 207 over 206 at its inner upper contact connects busy potential from the upperback contact of relay 215 over the normal contacts of thermostatic relay 217, resistance 218, contacts of relay 206 to conductor 201 in parallel with relay 202 for holding relay 117 of the district link circuit operated. At is innermost lower front contact relay 206 connects marking potential over the lower back contact of relay 211, the inner lower front contact of relay 206 to test terminals 301 of all trunk finders similar to trunk finder 300 of Fig. 3 and in parallel to ground through start relay 302. Relay 302 operates closing an obvious circuit for relay 303 which in turn establishes operating circuits for the stepping magnets of all idle trunk finders individualto idle registering devices. One of these registering devices is shown in Fig. 3 and it will be assumed that this registering deviceis idle and becomes connected with the trunk of Fig. 2. The operatin g circuit of trunk finder 300 of this register-. ing device may be traced from battery, through the winding and interrupter contacts of stepping magnet 304, a contact of relay 303 to'ground at the back contact of relay 305. When the calling trunk is found and test wiper 306 of trunk finder 300 engages terminal 301., the circuit previously traced to terminal 301 is extended over wiper 306, the upper winding of relay 305 to ground at the normally closed contacts of the oif-normal springs 354 of translator switch 330. Relay 305 thereupon operates opening the circuit of magnet 304 and closes an obvious circuit for relay 307 which at its lower front contact connects the low resistance winding of relay 305 into circuit with wiper 306 to busy the trunk circuit to other trunk finder switches.

Relay 307 also closes a circuit in parallel through the windings of relays 210 and 211 over wiper 308, the innermost upper front contact of relay 307, resistance 355, normal terminal and wiper 309 of register 310, normal terminal and wiper 311 of register 320 to ground at the back contact of relay 312. Relay 210 operates to close the outgoing trunk circuit so that the subscriber may receive a dial tone incoming over the trunk circuit. Relay 211 being marginal does not, however, operate at this time because of the resistance in its operating circuit. The continuity of the loop circuit over the outgoing trunk circuit is not, however, broken by the operation of relay 210 since it is maintained through the winding of supervisory relay 212.

When the calling subscriber receives dialing tone incoming over trunk conductors 207 and 208 and transmittedover front contacts of relay 210, he proceeds to dial the digits of the wanted line number. It will be asthe winding of relay 3 12 in a circuit extending from ground at the lower back contact of relay 204, the intermediate lower front contact of relay 206, wiper 313, the upper inter mediate front contact of relay 307, windin of relay 312, inner upper back. contact 0 relay 314, back contact of relay 315 to battery through the winding of stepping magnet 316 of the register 310. Relay 312 operates in this circu1t and being slow to release remains energized during the transmission of the series of impulses and at its back contact opens the previously traced circuit of relay 210 which thereupon deenergizes and shunts the winding of relay 212 from the outgoing trunk dialing loop'for permitting the better repetition of impulses over the outgoing trunk circuit. At its upper contacts relay 204 repeats impulses over the outgoing trunk circuit. As, however, this invention is not concerned with the repetition of impulses over the outgoing trunk no further reference will be made thereto herein. The first digit dialed thus sets the register 310 into its seventh position and upon the termination or the impulses relay 312 releases and closes a circuit for relay 315 extending from battery,

winding of rela 315, off-normal terminals and wiper 309 o register 310, normal terminal and wiper 311 of register 320 to ground at the back contact of relay 312. Relay 315 energizes and locks over its lower contact to ground applied to conductor 353 at the upper front contact of relay 307, and switches the impulsing circuit previously traced from the winding of magnet 316 of register 310 over the upper back contact of relay 322 to the winding of magnet 317 of register 320.

The second digit four dialed by the calling subscriber now sets the register 320 to its fourth terminal position. Immediately the second digit register 320 moves 01f normal, the rotation of translator switch 330 is started by a circuit extending from battery, through the winding and interrupter con tacts of magnet 318, the olf-normal terminals and wiper 319, lower back contact of relay 321, lower back contact of relay 322, to

ground on conductor 353. The terminals in the lowermost bank of register 320 are connected in pairs 1, 2; 3, 4; etc., and are connected by jumpers to terminals 1, 11, 21, etc., in the marking level of the translator switch 330. The translator switch hunts for the marked terminal under the control of test relay 321, but if the first terminal is marked the switch does not move since relay 321 will operate immediately when register 320 leaves normal over a circuit extending from battery, wiper 323, No. 1 terminal 324 and wiper 325 of translator switch 330, upper normal contacts of relay 314 to ground through the winding of relay 321. When the marked terminal 326 is found, relay 321 operates over the circuit just traced, opening the circuit of stepping magnet 318. Vhen the relay 312 again deenergizes upon the termination of the second series of impulses, with relay 321 operated a circuit is closed for relay 322 extending from battery, winding of relay 322, front contact of relay 321, off-normal terminals and wiper 311 of register 320 to ground at the back contact of relay 312. Relay 322 operates and locks to ground on conductor 353.

In response to the dialing of the third digit one, an impulse is repeated by the impulsing relay 204 as before traced through the winding of relay 312, thence over the upper front contact of relay 315, the upper front contact of relay 322 to battery from the Winding of stepping magnet 318. It was assumed that the third digit was one and therefore the translator wipers are advanced one step further. As'soon as wiper 325 leaves terminal 326, the circuit of relay 321 is opened. When relay 312 again deenergizes upon the termination of the third digit series of impulses a circuit is established for relay 314 extending from battery through the winding of relay 314, inner lower front contact of relay 322, back contact of relay 321, thence as traced to ground at the back contact of relay 312. Relay 314 upon operating locks over its inner lower front contact to ground on conductor 353.

The terminals of the four upper levels of translator switch 330 aremultipled in accordance with the size of the various oflices of the exchange and are jumpered to the points 336, 337 and 338 in accordance wlth the distance between the originating office and the other offices. It will be noted that the even numbered terminals of the bank associated with wiper 341 are multipled to the wiper switching relay 333 and that as the second digit dialed was four, or of even value, relay 333 is operated over wiper 341 and the inner upper front contact of relay In addition the sixth and seventh terminals in the bank of register 310 to which wiper 342 has access are connected to the armatures of relay 333 and in accordance with the energized or deenergized condition of this relay, are connected to either wipers 343 and 344, or 345 and 346 of the translator switch. Since it has been assumed that the register 310 was set into its seventh terminal position and that relay 333 is operated, wiper 344 only is connected in a circuit over wiper 342, the intermediate lower front contact of relay 314 to ground on conductor 353. Since also the translator has been adtit the inner upper front Contact of relay 307,

wiper 308 to battery through the windings of relays 210 and 211 thereby causing the operation of these relays. It having been assumed that connection is to be made with the line of a local subscriber which may be reached over the wipers of group selector 110, no cross-connection is made between terminal 357 and the cross-connection points 336, 337 and 338 and therefore relays 213, 214 and 339 are not operated at this time and no discriminating signal is therefore sent to the district link circuit over conductor 216 upon the operation of relay 215.

At its upper back contact relay 215 disconnects battery potential from conductor 201 thereby releasing relay 117 in the link circuit in turn releasing relay 123. The release of relay 123 in turn opens the circuit of relay 204 in the trunk circuit releasing relays 205 and 206 of the trunk circuit and relays 305 and 307 of the register circuit. The release of relay 307 removes holding ground from conductor 353 thereby releasing operated relays 314, 315, 322 and 332 and in turn releasing relay 333 and 215. A circuit is now established for restoring the register 320 extending from battery, through the winding and interrupter contacts of magnet 317, off-normal terminals and wiper 348 of register 320, back contact of relay 307 to ground at the off-normal contacts 354 of translator switch 330. When the register 320 reaches normal the operating circuit for magnet 316 of register 310 is established from battery, through the winding and interrupter contacts of magnet 316, wiper 349 and the off-normal terminals of the bank with which it cooperates, the normal terminal and wiper 348 of register 320, thence to ground as traced to oil-normal contacts 354. When the register 310 reaches normal the operating circuit of magnet 318 of translator switch 330 is established from battery through the winding and interrupter contacts of magnet 318, the normal terminal and wiper 349 of register 310, thence as traced to ground. Its restoring circuit is opened when the translator reaches normal and opens contacts 354. Trunk finder 300 has no normal position and remains in contact with the terminals of the trunk circuit last used. All apparatus of the trunk circuit of Fig. 2

and register of Fig. 3 isnow in normal condition.

At the district link circuit of Fig. l u on the release of relay 123 the windings of re ay 126 are connected to the calling line loop over the contacts of relay 109 before slow to release relay 124 has had time to release following the release of relay 123, and a new holding circuit for relay 124 is therefore established over'the upper front contact of relay 126 to ground over conductor 138 and the upper front contact of relay 109. When the calling subscriber now dials the tens digit which was assumed to be two, relay 126 releases for each impulse and establishes a circuit for the tens marking switch magnet 132 which extends from battery, through the.

winding of magnet 132, lower back contact of relay 133, winding of relay 134, back contact of rela 113, which released upon the operation 0 relay 126, back contact of relay 126 to ground on conductor 138. Slow to release relay 134 operates in series with magnet 132 and remains operated until the tens Series of impulses terminates.

As soon as the marking switch 140 leaves normal the group selector 110 starts hunting by reason of a circuit for its stepping magnet extending from battery, through the winding of magnet 114, lower back contacts of rela s 115and 116, off-normal terminals and wiper 135 of marking switch 140 to ground at the back contact of relay 117. When the impulses of the tens digit have been comp'letel transmitted relay 134 releases and a circuit 1s established in parallel from battery, through the upper winding of relay 136 and the winding of relay 133, over the lower normal contacts of relay 118, wiper 137 and off-normal terminals of switch 140, back contact of relay 134, inner upper back contact of relay 118 to off-normal ground on con ductor 138. Relay 133 looks itself operated over its inner lower front contact to ground at the back contact of relay 142 and changes the impulsing circuit controlled by relay 126 from the winding of magnet 132 to the winding of magnet 139 of units marking switch 150 which is now set in response to the dialing of the units digit five. Relay 136 locks over its locking contact and lower winding and back contact of relay 145 to off-normal ground on conductor 138..

When the group selector 110 reaches the terminal 170 of its marking level marked by the setting of the tens marking switch 140, the marking switch having been positioned in position 2, a circuit is established for relay 117 which may be traced from battery, offnormal terminals and wiper 141 of marking 1 switch 140, winding of relay 117, wiper 121,

terminal 17 0, wiper 119 to ground at the upper back contact of relay 118. Relay 117 now opens the circuit of the stepping magnet 114 of the group selector and closes the circuit of relay 118 extending from battery, through the upper winding of relay 118, the upper intermediate front contact of relay 133 to ground at the front contact of'relay 117. Relay 118 then looks over its lower winding and inner lower front contact to off-normal ground on conductor 138 and switches marking ground at its upper contacts from wiper 119 of marking switch 140 to the wiper 143 of the units of mark ng switch 150. Until the marking switch 150 moves beyond its first terminal position relay 117 is held op erated from ground over wiper 143, wiper 119, terminal'170, wiper 121, thence as traced through the winding of relay 117 to battery at wiper 141 so that if the units digit is one the group selector does not move further.

It has been assumed, however, that the units digit dialed was five and therefore when marking switch 150 moves beyond position 1, relay 117 releases and closes the circuit of magnet 114 of the group selector to ad- Vance it one step whereupon relay 117 again operates. In this'manner the group selector follows the setting of the units marking switch step by step. When the units series of impulses-ceases, relay 134 again deenergiyes and establishes a circuit for relay 142 extending from battery, through the winding of relay 142, off-normal terminals and wiper 144, of the units marking switch .150, lower front contact of relay 118, off-normal terminals and wiper 1.37 of tens marking switch 140,

back contact of relay 134, inner upper front contact of relay 118 to ground at the front contact of relay 117. Relay 142 opens the locking circuit of relay 133 and during the releasing time of slow to release relay 133 a circuit is established for the test relay 146 extending from ground at the upper front contact of relay 142, the inner upper front contact ofrelay 133, upper winding of relay 146 to the test wiper 122,. thence over the test terminal of the wanted line 160 to battery through the cut-off relay 148. If the line is idle, relays 148 and 146 operate and relay 146 locks over its lower winding and intermediate lower contact to off-normal ground on conductor 138. At its upper front contacts relay 146 switches through the talking connection from wipers 127 and 131 through condensers 149 and 151 back contacts of relay 123 and front contacts of relay 109 to wipers 128 and 129. At its inner lower front contact the test wiper 122 is connected to test wiper 125 so that the cut-off relays 103 and 148 of the calling and called lines are connected in parallel through the winding of relay 109 to ground at the front contact of relay 124.

Ringing current is now applied to the calling line from the ringing current source 152 through thewinding of ringing cut-olf relay 145,'tl1e upper front contact of relay 136, the inner upper front contact of relay 146, wiper 131, thence over the called line 160 and through the substation bell returning over wiper 127, the upper front contact of relay 146, the inner upper front contact of relay 136 to ground at the lower front contact of relay 142. A ringing tone is transmitted to the calling line over the upper back contact of relay 133, condensers 153 and 151, thence as traced over the calling line. When the called subscriber answers, relay 145 energizes releasing relay 136 to disconnect the source of ringing current and ringing tone and to connect the windings of the back bridge relay 154 to the conductors of the called line. Relay 154 now operates in a circuit extending from battery, through its lower winding, upper back contact of relay 136, inner upper front contact of relay 146, wiper 131, thence over the called line, returning over wiper 127, the upper front contact of relay 146, to ground throughthe upper winding of relay 154.

A circuit is now effective for operating the calling line message register 155 which may be traced from ground, through the Winding of message register magnet 155, wiper 156, lower front contact of relay 146 to battery through the inner lower back contact of relay 1-36. Upon the termination of the conversation, when the calling subscriber restores his receiver, relay 126 releases followed by the release inturn of relays 124 and 109. When relay 109 releases it removes holding ground from conductor 138 thereby releasing all other operated relays of the link circuit and releasing the cut-off relays 103 and 148 of the calling and called lines. lVith relay 124 deenergized, a restoring circuit is established for marking switch 140 extending from battery, through the winding and interrupter contacts of magnet 132, off-normal terminals and wiper 157, to ground at the back contact of relay 124. When switch 140 reaches normal the winding of magnet 132 is disconnected from wiper 157 and ground from wiper 157 is extended over wiper 158 and the off-normalterminals of its bank through the interrupter contacts and magnet winding 139 of marking switch 150. Switch 150 is thereby restored to normal in which position the circuit of magnet 139 is opened. Group selector 110 returns to normal upon the seizure of the link circuit for the next call.

If the calling subscriber holds the line for thirtyseconds after the called subscriber restores his receiver and releases back bridge relay 154, a circuit becomes established for the thermostatic relay 112 extending from battery, through the winding of relay 112, the lower front contact of relay 126, the upper back contact of relay 154, the inner upper back contact of relay 136 to ground at the lower front contact of relay 142 which is effective to connect battery over the upper contacts of jack 107, wiper 111, the back contact of line relay 102 to ground through the upper winding of fault relay 159. Relay 159 upon operating locks over its lower winding in a circuit extending over the calling line to round at the upper contact of relay 159, and at its inner upper front contact connects a shunt over wiper 125 thereby causing relay 109 to deenergize and release the connection. The calling line cut-off relay 103 is also operated by relay 159 thereby preventing the line relay 102 from reoperating and an alarm circuit is closed over the lower contact of relay 159 to apprise the attendant that the calling subscriber has not restored his receiver as he should. As soon as the calling subscriber hangs up, relay 159 releases and restores the calling line to its normal condition.

In the foregoing description it was assumed that the wanted local line was reached over the wipers of the group selector 110. It will now be assumed that the calling subscriber dialed the number 73125 of a local line terminating in the bank of group selector 120. The circuits function in the manner previously described up to the point where the first three digits have been registered in the register translator. Since the second digit registered by the register 320 is now assumed to ,be three, the translator brush 346 is set upon terminal 350 and upon the energization of relay 314, following the termination of the third impulse series, the circuits of relays 332 and 215 are again closed and in addition relay 213 is operated in a circuit extending from ground on wiper 346, terminal 350, cross-connection point 336, the inner upper front contact of relay 332, wiper 334 to battery through the winding of relay 213. lVith relay 332 operated, the circuit of relay 211 is established as previously described, locking itself and relays 213 and 215 to off-normal ground on conductor 221.

lVith relay 215 operated the holding circuit of relay 117 is opened, releasing this relay and in turn releasing relay 123. A circuit is now closed from ground, through re sistance 219, over front contacts of relays 213 and 215, conductor 216, thence over wiper 161, the lower back contact of relay 123 to battery through the windings of relays 115 and 116. Relay 116 being marginal, only relay 115 operates in this circuit, locking over its inner upper front contact and the upper back contact of relay 116 to ground on conductor 138. At its lower back contact relay 115 disconnects the winding of stepping magnet 114 of group selector 110 and at its lower front contact connects the winding of stepping magnet 162 of group selector 120 in a circuit extending over the lower back contact of relay 116 to the off-normal terminals associated with wiper 135 of the tens marking switch 140 preparatory to advancing the wipers of the group selector 120 as soon as the tens marking switch operates in response to the dialing of the tens digit. Relay 115 also establishes a circuit extending from ground at its upper front contact, over the off-normal contacts 168 of selector 110 to battery through the interrupter contacts and magnet winding of magnet 114 whereby the group selector 110 is restored to normal releasing the selected trunk circuit. All appa-- ratus associated with the trunk circuit is then restored in the manner previously described.

In response to the dialing of the tens and units digits the marking switches 140 and 150 are set as previously described and the group selector 120 is started in its group or. tens selection movement as soon as the wiper 135 leaves normal. \Vhen the selector wipers reach the set of terminalsv marked by the tens marking switch 140, the wiper 164 will be in engagement with terminal 165 and the further movement of the group selector will be stopped by the operation of relay 117. The units selection movement of the group selector is then controlled by the setting of the marking switch 150 in the same manner as previously described in connection with the marking switches 140 and 150 to normal.

When the marking switches have both reached their normal positions a restoring circuit forgroup selector 120 is then established from battery, through the winding and interrupter contacts of magnet 162, off-normal contacts 166, normal terminal and wiper 158 of switch 150, normal terminal and wiper 157 of wiper 140 to ground at the back contact of relay 124 thereby restoring the group selector 120 to normal. 1

Had the calling subscriber dialed the number 64125 of a local subscriber whose line terminates in the bank of groupselector 130 the circuits would have functioned as previously described up to the point where the translator 330 was set in response to the dialing of the third digit except that the register 310 would have been set into position six rather than position seven and register 320 would have been set into position four. In this case following the termination of the dialing of the third digit and the operation of relay 314, with relay 333 operated, the wiper 343 of the translator is made effective and since wiper 343 is now standing on terminal 351 a circuit is established for relay 332 which in turn operates relay 215. Terminal 351 is also connected by a jumper to cross-connection point 337 so that upon the operation of relay 332 the operating circuit of relay 332 is extended over the lower contact of relay 332, brush 335 to battery through the winding of relay 214. Relays 214 and 215 upon operating both lock over a front contact of relay 211 to off-normal ground on conductor 221.

With relay 215 operated the holding circuit of relay 117 is opened releasing relay 117 and in turn releasing relay 123. A circuit is now closed from "ground at the inner lower front contact of relay 214, the lower front contact of relay 215 to conductor 216, thence over wiper 161, the lower back contact of relay-123 to battery through the windings of relays 115 and 116. Both of these relays operate in this circuit locking over the upper front contacts of relay 116 to ground on conductor 138. At its lower back contact relay 115 disconnects the winding of stepping magnet 114 of group selector 110 and at its lower front contact relay 116 connects the winding of stepping magnet 167 of group selector 130 in a circuit extending over the lower front contact of relay 116 to the off-normal terminals associated with wiper 135 of the tens marking switch 140 preparatory to advancing the wipers of group selector 130 as soon as the tens marking switch operates in response to the dialing of the tens digit. Relay 115 also establishes a circuit extending from ground at its upper front contact over the off-normal contacts 168 of the selector 110 to battery through the interrupter contacts and ma net winding of magnet 114 whereby group se ector 110 is restored to normal releasing the selected trunk circuit. All apparatus associated with the trunk circuit is then restored in the manner previousl described. From this point the circuits 0 Fig. 1 function in the manner previously described except that the marking switches 140 and 150 mark terminals in the marking level, not shown, of group selector 130 to set this group selector upon the terminal of the wanted line. I

In the foregoing description it has been assumed thatlthe first three digits dialed by the calling subscriber indicated that a connection was desired with a local subscribers line. If, however, these digits had for example been 742, indicative of a connection to'be com leted beyond the district or community o ce, then following the completion of dialing the third digit and the operation of relay 314, no immediate circuit would be completed for relay 332 as the translator bank terminal 352 upon which the wiper 344 is then resting is not cross-connected to crossconnection point 349. Conse uently relav 215 is not at this time operated to cause the release of the trunk circuit and the remaining two digits of the line number dialed bv the calling subscriber are received 'in the register translator circuit.

- No record of the denomination of the fourth and fifth digits dialed is taken in the register circuit, but pairs of relays 327, 328

and 329, 331 are energized at the beginning and end of the tens and units di 't series respectively under the control 0 relay 312. 'Thus, at the beginning of the fourth or tens digit a circuit is established from battery,

through the Winding of relay 327, back contact of relay 328, lower front contact of relay 314 to ground at the front contact of relay 312. Relay 327 thus operates lockmg through the winding of relay 328 and over its own contact to ground on conductor. 353 but relay 328 being shunted does not operate. When relay 312 deenergizes, however, at the end of the tens digit series, relay 328 operates. At the beginning of the fifth or units digit series relay 312 again operates and establishes a circuit for relay 329 extending from battery through the winding of this relay, front contact of relay 328,,thence as traced to ground at the front contact of relay 312. Relay 329 operates and locks in series with relay 331 over its own front contact to ground on conductor 353, but relay 331 being shunted at the front contact of relay 312 does not energize in this locking circuit. When, however, relay 312 deenergizes at the end of the units digit series relay 331 operates and establishes a circuit for relay 332 extending from battery through the Winding of relay 332, the front contact of relay 331 to ground on conductor 353.

Metering control relays 213 and 214 are now connected over wipers 334 and 335 of the trunk finder 300 and front contacts of relay 332 to cross-connecting points 336 and 337 of cross-connecting rack 340. A further point 338 is connected b relay 332 to the "winding of relay 339. t will-be assumed "that for the particular setting of the translator switch in response to the digits 742 the translator bank terminal 352 is jumpered to the point 338 and that therefore following the operation of relay 332, a circuit is established for relay 339 extending through the winding of relay 339, over the inner lower front contact of relay 332, terminal 352,

- wiper 344, lower front contact of relay 333 which was operated with register 320 in position 4, the seventh terminal and wiper '342 of register 310, the intermediate lower front contact of relay 314 to ground on conductor 353. Relay 339 upon operating completes the circuits of bothrelays 213 and 214. Had

the first three digits dialed been, for example, 732 or 642, then upon the operation of relay 332 the relay 339 would not be operated, but either relay 213 or relay 214 would be operated singly. Thus dependent upon the first digits dialed three metering conditionsmay be established by the operation of both or either of relays 213 and 214.

In addition to selectively operating the meter control relays 213 and 214, relay 332 connects direct groundover its upper contact, the inner upper front contact of relay 307, wiper 308 to battery through the windstrumental in setting up a connection at a distant oilice to the line of a desired subscriber. When such subscriber answers the circuit extending over conductor 208 is momentarily opened thereby releasing relay 212. Relay 212 upon releasing now closes a circuit for relay 220 extending from battery, through the winding of relay 220, upper front contact of relay 211, upper back contact of relay 212 to ground on conductor 221. Relay 220 looks to conductor 221 and as soon as relay 212 again energizes, establishes a circuit for relay 209 extending over the upper front contact of relay 220, the front contact of relay 212 to ground on conductor 221. Relay 209 also looks to conductor 221 and establishes an obvious circuit for the time switch 222 which receives an impulse every two seconds from the master clock circuit.

A circuit is also established from battery, through the winding of metering switch magnet 223, wiper 224 and the normal terminal upon which it is resting, contact 225 of the time switch 222 to ground at the intermediate upper front contact of relay 209 for advancing the switch 200 one step off normal, from which position it rotates through a single cycle under the control of interrupter 226. As soon as the time switch 222 leaves normal it opens contact 225 so that when the metering switch 200 reaches normal its advance is arrested. With relays 213 and 214 both operated as previously described, when the wiper 227 of the meterin switch 200 passes over the first, third and fth terminals of its bank three metering impulses are transmitted over a circuit which extends from metering battery, through resistance 228, the upper front contact of relay 214, terminals and wiper 227 of switch 200, the lower back contact of relay 215, conductor 216, wiper 161, the lower front contact of relay 123, wiper 156 to ground through the message register magnet 155. These impulses are then followed by two further impulses transmitted from battery, through resistance 228, the lower front contact of relay 213, the seventh and ninth terminals and wiper 227 of switch 200, thence as traced through the winding of message register magnet 155.

After three minutes, timeswitch 222 again closes contact 225 and the metering switch 200 again completes a cycle transmitting five additional metering impulses. This sequence circuiting ground to the winding of relay 117 in the district link circuit over conductor 201, contact 230 to ground at the intermediate upper contact of relay 209. Relay 117 then releases in turn releasing relay 123 whereupon the calling line is disconnected from the windings of realy 204. Relay 204 then releases in turn releasing relays 205 and 206.v Following the release of relay 206 the trunk circuit and all apparatus which has been taken into use thereby is released.

Relay 123 upon releasing now connects the calling line as previously described to the windings of relay 126 which thereupon energizes. If the calling subscriber does not now restore his receiver within thirty seconds, the thermostatic relay 112 operates over the lower front contact of relay 126, the normal terminal and wiper 137 of marking switch 140, the back contact of relay 134, a back contact of relay 118 to off-normal ground on conductor 138. As'previously described, relay 112 causes the o eration of the calling line fault relay 159 w ich signals the attendant and causes the release of the district link circuit.

If the calling subscriber terminates the conversation prior to the completion of the tvelve minute period, the restoration of his receiver releases relay 204 followed by the release of relays 205 and 206 and the restoration of the remaining equipment employed in the connection. If, however, the calling subscribed holds the connection after the called subscriber hangs up, for a period of thirty seconds, a circuit is established for the thermostatic relay 217 extending over the lower back contact of relay 212, which releases when the called subscriber hangs up, thence to ground at the lower front contact of relay 220. After the expiration of thirty seconds, relay 217 closes its lower contact thereby connecting direct ground to conductor 201 for shunting down relay 117. The forced release of the connection is then caused in the manner previously described. Similarly after the out-pulsing loop over trunk conductors 207 and 208 is established by relay 204, if pulsing does not begin the circuit of relay 217 is established over the upper back contact of relay 211 and the inner upper front contact of relay 210 for a suflicient interval to to cause relay 217 to start the .forced release of the established connection.

In the preceding description it was assumed that both meter control relays 213 and 214 were operated and that thus for each unit period of conversation five metering impulses were transmitted by switch 200 for operating the calling line message register magnet. Had meter control relay 214 been operated alone it is obvious that but three metering impulses would have been trans-.

mitted and that similarly had relay 213 been operated alone but two metering impulses would have been transmitted.

If a community oifice of an exchange system has less than one hundred lines a link circuit of the type shown in Fig. 4 may be used in place of the link circuit of Fig. 1. Calling lines have access to this link circuit in the same manner as described in connection with Fig. 1 and the link circuit has access to outgoing trunks and register circuits the manner previously described thereby closing a start circuit for the line finder 1400 extending from battery, over the windingand interrupter contacts of stepping magnet 406, the lower back contact of relay 409,

contacts of relay 105 to ground at the back contact of relay 408. When the test wiper 411 of the line finder engages the test terminal of the calling line, battery potential is encountered and an operating circuit is established over the normal contact of thermostat1c relay 412, winding of test relay 408, contacts of test ack 407, normal terminal and -wiper 401 of the tens marking switch 430,

normal contacts of off - normal switches 402 and 403 in parallel of group selectors 410 and 420, inner lower normal contacts of relay 413 to ground atthe upper normal contacts of relay 409. Relay 408 then operates and opens the clrcuit of magnet 406 and closes an 'obvious circuit for relay 413.

With relay 413 operateddirect ground is connected to wiper 411 through the winding of relay 408, the inner lower front contact of relay 413 and the upper normal contacts of relay 409 to prevent the seizure of the calling line by another line finder, and a circuit is closed for stepping magnet 414 of the group selector 410 to advance the group selector to hunt for an idle outgoing trunk. This circuit extends from battery, through the winding and interrupter c'ontacts of magnet 414, wiper 404 and the strapped terminals of the upper half of the bank with which 1t is associated, the back contact of test relay 417 to ground at the lower front contact of relay 413. When an idle trunk is found relay 417 operates in a circuit extending from battery on the test-terminal of the idle trunk,

wiper 422, the upper front. contact of relay 413, winding of relay 417, wiper 421 and strapped terminals of the marking level of group selector 410 to ground over wiper 419 of the marking switch.

.Relay 417 now opens the circuit of magnet 414 to arrest the operation of the group selector 410 and establishes a circuit for relay 423 extending from battery, through the winding of this relay, the normal terminal and wiper 405 of the marking switch, front contact of relay 417 to ground at the lower front contact of relay 413. At its inner lower front contact relay 423 closes an obvious circuit for relay 424. Relay 424 upon operating establishes a circuit from ground, through the winding of relay 409, over wiper 425 of the line finder 400 to battery through the cut-off relay 103 of the calling line. Relay 103 disconnects the line relay 102 which in turn releases relay 408 and if there are at the time no other lines calling in' the group the start relay 105 is also released thereby arresting the operation of other line finders that may have been started. After the release of relay 408 relay 413 is locked over its inner upper front contact, the upper back contact of relay 426 to ground over conductor 438 and the inner upper front contact of relay 409.

With the relays 409 and 423 operated the calling line is extended over wipers 428 and 429 of line finder 400 and wipers 427 and 431 of group selector 410 to the selected trunk circuit. The trunk'circuit of Fig. 2 then functions in the manner previously described to connect itself with an idle registering device such as is disclosed in Fig. 3. In response to the dialing of the first three digits of the wantedd-ine number, which will be assumed to be 7 4325 indicative of a local subscribers line terminating in the bank of group selector 410, the registering device registers these digits and as previously described, causes the operation of relay 215 in the trunk circuit.

The operation of' relay 215 -nowcauses the release of test relay 417 in the link circuit followed by the release of relay 423 and also causes the release of all apparatus associated with the trunk circuit and the release of the registering device.

At the district link circuit of Fig. 4 upon the release of relay 423 the windings of relay 426 are connected to the calling line loop over the contacts of relay 409 before the slow to release relay 424 has time torelease following the release of relay 423, and a new holding circuit for relay 424 is therefore established over the upper front contact of relay 426 to ground on conductor 438. l/Vhen the calling subscriber now dials the tens digit which was assumed to be 2, relay 426 releases for each dial impulse and establishes a circuit for the marking switch magnet 432 which extends from battery, through the winding of magnet 432, the upper normal contact of relay 415, winding of slow to release relay 434, inner upper back contact of relay 413, which released upon the operation of relay 426, back contact of relay 426 to ground on conductor 438. Slow to release relay 434 operates in series with magnet 432 and remains operated until the tens series of impulses is terminated. When the marking switch leaves normal a circuit is closed for advancing the group selector 410 which may be traced from battery, through the winding and interrupter contacts of magnet 414, wiper 404, back contact of relay 417, off-normal terminals and wiper 416, lower normal contacts of relay 415 to ground on conductor438. When the tens digit impulses terminate and the test wiper 421 reaches terminal 442 marked by wiper 419 of the marking switch a circuit is completed for relay 417 extending from ground on wiper 419, terminal 442, wiper 421 winding of relay 417 to battery at the upper back contact of relay 413.

With relay 417 operated the circuit of magnet 414 is opened to arrest further movement of the group selector and a circuit is established for relay 415 extending from battery through the windings of relay 415, off-normal terminals and wiper 405, front contact of relay 417, off-normal terminals and wiper 416, inner lower normal contacts of relay 415 to ground on conductor 438. Relay 415 locks over its windings and inner lower front contact to ground on conductor 438. When the calling subscriber now dials the units impulses the stepping magnet 414 is operated directly from the contacts of relay 426 in a circuit extending from battery, through the winding of magnet 414. terminals of the upper half of the'bank with which wiper 418 is associated and wiper 418 of marking switch 430, upper alternate contacts of relay 415, winding of relay 434, inner upper back contact of relay 413, back contact of relay 426 to ground on conductor 438. Therefore the wipers of switch 410 are positioned in response to the dialing of the units digit upon the terminal of the wanted line. Relay 434 operates in this stepping'circuit and establishes a circuit for relay 433 extending from battery, winding of relay 433, inner upper ront contact of relay 415 to ground at the front contact of relay 434 which in turn establishes an obvious circuit for relay 436. Relay 436 upon operating locks over the back contact ofrelay445 and the lower front contact of relay 436 to ground on conductor 438. When the last units impulse is received relay 434 releases followed by the release of slow releasing relay 433.

If the called line is free, test relay 446 energizes before relay 433 releases in a circuit extending over test wiper 422, the upper winding of relay 446, the upper front contact of relay 433 to ground at the back contact of relay 434. Relay 446 operates and locks over its lower winding and intermediate lower front contact to ground on conductor 438. The calling subscribers bell is then rung by ringing current applied, from source 452 through the winding of ring cut-off relay 445, the inner lower alternate contacts of relay 436, the inner upper front contacts of relay 446, wiper 431 thence through the substation bell, wiper 427, the lower front contact of relay 446, the lowermost front contact of re lay 436 to ground on conductor 438 and upon the response of the called subscriber relay 445 operates releasing relay 436 to disconnect the ringing current source 452. Back bridge relay 454 thereupon o erates over the called line and the calling line messageregister is operated in the same manner previously describedin connection with Fig. 1.

Upon the termination'of the conversation the calling subscriber restores his receiver to the switchhook releasing relay 426 which in turn releases relays 424 and 409. Relay 409 in turn removes ground from conductor 438 releasing relays 415 and 446. 'A restor ing circuit is now effective for returning the group selector 410 to normal which may be traced from battery, through the winding and interrupter contacts of magnet 414, offnormal switch 402, lower normal contacts of relay 413 to ground at the upper normal contacts of relay 409. When the group selector .reaches normal the circuit of magnet 414 is opened at contacts 402 and a circuit is closed for returning the marking switch 430 to normal extending from battery, through the winding and interrupter contacts of magnet 432, off normal terminals and wiper 401, oil-normal contacts 402, thence to ground at the upper normal contacts of relay'409.

It will be noted that if the tens digit of the wanted local subscribers number is less than five, the group selector 410 will be employed to complete the connection just described. If, however, in response to the impulses of the tens digit the marking switch advances more than five steps, the stepping circuit previously traced for stepping magnet 414 is opened when .wiper 404 leaves its fifth terminal and the further movement of the group selector 410 is arrested and the stepping circuit of group selector 420 is made effective over the lower half of the bank of terminals to which wiper 404 has access. This group selector then advances to the group terminal marked by the wiper 419. When the group selection is completed and relay 415 operates as previously described the group selector 420 is then set directly upon the terminal of the wanted line by the impulses ofthe units digit by a circuit extending over the lower half of the bank of terminals to which wiper 418 has access. The circuits then function as previously described except that when the calhng subscriber hangs up the restoring circuit previously traced from ground at the upper normal contacts of relay 409,,over the lower normal contacts of relay 413 extends in parallel through the oil'- normal switch contacts 402 and 403 for re storing both group selectors to normal.

In the event that either subscriber engaged in a local connection over a link circuit of the character disclosed in either Fig. 1 or Fig. 4 is desired for a toll connection, the toll operator upon connection with multiples of either line may apply direct ground to the winding of either relay 109 or relay 409 thereby releasing the link circuit and releasing the local connection. 30

What is claimed is:

1. A telephone exchange system comprising a link circuit-terminating at one end in a plurality of parallelly connected selector switches, a group of outgoing trunk circuits terminating in the terminal bank of one of said switches, subscribers lines terminating in the banks of all of said switches, a calling line, means for associating said calling line with said link circuit, means responsive to such association for operating one of said switches to select an idle trunk circuit, means associable with said selected trunk circuit for registering certain digits of a wanted line number. means in said link circuit responsive to other digits of a wanted line number for causing the operation of one of said switches to connect with a wanted line, and means controlled by said registering means to render said latter means efi'ective only if said certain digits indicate that the connection is to be terminated locally.

2. A telephone exchange system comprising a link circuit terminating at oneend in a plurality of parallelly connected selector switches. a group of outgoing trunk circuits terminating in the terminal bank. of one of said switches, subscribers lines terminating in the remaining terminals of the banks of said switches, a calling line, means for associating said calling line with said link circuit, means responsive to such association for operating one of said switches to select an idle trunk circuit, means associable with said selected trunk circuit for registering certain digits of a wanted line number, means controlled by said registering means if said certain -digits registered therein indicate that the call is to be terminated locally for advancing said one switch to release said trunk, and means"'in said link circuit for then operating one of said switches in response to the dialing ot' the remaining digits of the wanted line number to extend the calling line toone of said other subscribers lines.

3. A telephone exchange system comprising a link circuit terminating at one end in a plurality of parallelly connected selector switches. a group of outgoing trunk circuits terminating in the terminal bank of'one of said switches, subscribers lines terminating in the remaining terminals of the banks of said switches, a calling line, means for associating said calling line with said link circuit, means responsive to such association for operating one of said switches to select an idle trunk circuit, means associable when said selected trunk circuit for registering certain digits of a wanted line number, means controlled by said registering means if said certain digits registered therein indicate that the call is to be terminated locally for transmitting a signal back to said link circuit, means responsive to said signal for releasing said trunk circuit, and means for rendering a particular one of said switches responsive to further digits dialed by the calling subscriber for selecting one of said other subscribers lines.

4. A telephone exchange system comprising a link circuit terminating at one end in a' plurality of parallelly connected selector switches, a group of outgoing trunk circuits terminating in the terminal bank of one of said switches, subscribers lines terminating in the remaining terminals of the banks .of said switches, a calling line, means for associating said calling line with said link circuit, means responsive to such association for operating one of. saidswitches to select an idle trunk circuit, means associable with said selected trunk circuit for registering certain digits of a Wanted line number, means controlled by said registering means if said certain digits registered indicate that the call is to be terminated locally for transmitting discriminating signals back to said link circuit, and means responsive to said signals for releasing said trunk circuit and for selecting a particular one of said switches for response to further digits dialed by the calling subscriber for selecting one of said other subscribers lines.

5. A telephone exchange system comprising a link circuit terminating at one end in a plurality of parallelly connected selector switches, a group of outgoing trunk circuits terminating in the terminal bank of one of said switches. subscribers lines terminating in the remaining terminals of the banks of said switches, a calling line. means for asso ciating said calling line with said link circuit, means responsive to such association for operating one of said switches to select an idle trunk circuit. means associable with said selected trunk circuit for registering certain digits of a wanted line number. means controlled by said registering means if said certain digits registered indicate that the call is to be terminated locally for transmitting discriminating signals in accordance with the registered digits back to said link ircuit. means responsive to said signals for releasing said trunk circuit and for selecting that one of said switches which has access to the group of subscribers lines in which the wanted line is located, and means responsive to the dialing of further digits for setting the selected switch upon the terminals of the wanted line.

6. A telephone exchange system comprising a link circuit terminating at one end in a plurality of parallelly connected selector switches, a group of outgoing trunk circuits terminating in the terminal bank of one of said switches, subscribers lines terminating in the remaining terminals of the banks of said switches, a calling line, means for associating said calling line with said link circuit, means responsive to such association for operating one of said switches to select an idle trunk circuit, means associable with said selected trunk circuit for registering certain digits of a wanted line number, means controlled by said registering means if said certain digits registered indicate that the call is to be terminated locally for transmitting discriminating signals varying in potential in accordance with the registered digits back to said link circuit. means responsive to said signals for releasing said trunk circuit and for selecting that one of said switches which has access to the group of subscribers lines in which the wanted line is located, and means responsive to the dialing of further digits for setting the selected switch upon the terminals of the wanted line.

7. A telephone exchange system comprising a trunk circuit terminating at one end in a plurality of parallelly connected selector switches. a group of outgoing trunk circuits terminating in the terminal bank of one of said switches, subscribers lines terminating in the remaining terminals of the banks of said switches, a calling line. means for associating said calling line with said link circuit, means responsive to such association for operating one of said switches to select an idle trunk circuit, means associable with said selected trunk circuit for registering certain digits of a wanted line number, means controlled by said registering means if said certain digits registered indicate that the call is to be terminated locally over that switch which has access to said trunk circuits for releasing said trunk circuit and for rendering said switch responsive to the dialing of further digits for selecting a wanted subscribers line terminating therein.

8. A telephone exchange system comprising a link circuit terminating at one end in a plurality of parallelly connected selector switches. a group of outgoing trunk circuits terminating in the terminal bank of one of said switches, subscribers lines terminating in the remaining terminals of the banks of said switches, a calling line, means for associating said calling line with said link circuit, and means responsive to such association for operating'said one ofsaid switches to select an idle outgoing trunk circuit.

9. A telephone exchange system comprising a link circuit terminating at one end in a plurality of parallellyconnected selector switches, a group of outgoing trunk circuits terminating in the terminal bank of one of said switches, subscribers linesterminating in the remaining terminals of the banks of said switches, a calling line, means for associating said calling line with said link cir-. cuit, means responsive to such association for operating said one of said switches to select an idle outgoing trunk circuit, means for registering dialed digits, and means controlled by said registering means for releasing the selected trunk circuit and for setting one of said switches to select a desired one of said subscribers lines.

10. A. telephone exchange system comprising a link circuit terminating at one end in a plurality of parallelly connected selector switches, a group of outgoing trunk circuits terminating in the terminal bank of one of said switches, subscribers lines terminating in the remaining terminals of the banks of said switches, a calling line, means for associating said calling line with said link circuit, means responsive to such association for operating said oneof said switches to select an idle outgoing trunk circuit, means for registering dialed digits, and means controlled by said registering means for releasing the selected trunk circuit and for either resetting said one switch or for setting one of said other switches to select a desired one of said subscribers lines.

11. A telephone exchange system comprising a link circuit terminating at one end in a plurality of permanently paralleled selector switches,-a calling line, means for associating said line with said link circuit. trunk circuits and subscribers lines terminating in the bank of one of said switches, subscribers lines terminating in the bank of the other of said switches, and means controlled over said calling line for operating said switches to connect with a trunk circuit or with a desired one of said subscribers lines.

12. A. telephone exchange system comprising a link circuit terminating at one end in a plurality of permanently paralleled selector switches, a calling line, means for associating ing a link circuit terminating at one end in a selector switch, a calling line, means for associating said line withsaidclink circuit, subscribers lines terminating in the bank of said selector switch, means controlled over said calling line for extending a conversational connection over said selector switch to a desired line, and thermostatic means operative to restore the established connection a predetermined interval after the called subscriber has restored his receiver if said calling subscriber has not restored his receiver.

14. A telephone exchange system comprising a link circuit terminating at one end in a plurality of permanently paralleled selector switches, a calling line, means for-associating said line with said link circuit, subscribers lines terminating in the banks of-said selector switches, means controlled over said calling line for operating said switches to extend a conversational connection with a desired one .of said subscribers lines, and means operative a predetermined interval after the called subscriber has restored his receiver if the calling subscriber has not restored his receiver. for releasing the extended connection.

15. A telephone exchange system comprising a link circuit terminating atone end in a selector switch, a calling line, means for associating said line with said link circuit, trunk circuits terminating in the bank of said selector switch, means responsive to the association of said line with said link circuit for operating said selector switch to select an idle trunk circuit, means in said trunk circuit responsive to the response of a called subscriber connected thereover and means in said trunk circuit operative a predetermined interval after the called subscriber has restored his receiver if the calling subscriber has not restored his receiver for releasing the connection.

16. A telephone system comprising a link circuit terminatingin a plurality of permanently paralleled selector switches, a calling line, means for associating said line with said link circuit, subscribers lines terminating in the bank of one of said switches, subscribers lines terminating in the bank of the other of said switches, a marking switch controllable by said calling line to direct the setting of any one of said switches in a first selection movement, and means for further setting such switch in a further selection movement directly under the control of said calling line.

17. A telephone exchange system comprising a link circuit terminating at one end in. a plurality of parallelly connected selector switches, a group of outgoing trunk circuits terminating in the terminal bank of one of said switches, subscribers lines terminating in the remaining terminals of the banks of said switches, a calling line,-means for associating said calling line with said link circuit, means responsive to such associaton for opcrating one of said switches to select an idle trunk circuit, means associable with said selected trunk circuit for registering certain digits of a wanted line number, means controlled by said registering means if certain digits registered therein indicate that the call is to be terminated locally for advancing said one switch to release said trunk, a marking switch in said link circuit operable in accordance with a further digit dialed by said calling subscriber for directing one of said selector switches in aline group selection movement, and means operative in response to a further dialed digit to directly set said selector to select the terminals of a desired subscribers line.

18. A telephone exchange system comprising a link circuit terminating'at one end in a plurality of parallelly connected selector switches, a group of outgoing trunk circuits terminating in the terminal bank of one of said switches, subscribers lines terminating in the remaining terminals of the banks of said switches, a calling line, means for associating said calling line with said link circuit, means responsive to such association for operating one of said switches to select an idle trunk circuit, means associable with said selected trunk circuit for registering certain digits of a wanted line number, means controlled by said registering means if certain digits registered therein indicate that the call is to be tern'linated locally for transmitting discriminating signals back to said link circuit, means responsive to said signals for releasing said trunk circuit and for selecting a particular one of said switches for response to further digits dialed by the calling subscriber, a marking switch in said link circuit operable in accordance with one of said further digits dialed for directing the selector switch in a line group selection movement, and means operable in response to a further one of said digits to directly set such selector to select the terminals of a desired subscrib-.

ers line.

In witness whereof we hereunto subscribe our names this 19th day of February, 1930. WILLIAM. HATTON. CHARLES DE VRIENDT. ERNEST JEAN ROUSSEAU.

Images