US2248566A - Telephone system - Google Patents

Description

July 8, 1941. A. J, BUSCH 2,248,566

. TELEPHONE SYSTEM Filed Apr il 19, 1939 14 Sheets-Sheet 1 g I IHI- L]:

@ lNl/ENTOR B AJBUSCH ATTORNEY July 8, 1941. A. J. BuscH TELEPHONE SYSTEM 14 Shets-Sheet 2 Filed April 19, 1959 July 8, 194 1.

A. .1. BUSCH TELEPHONE SYSTEM l4 Sheets-Sheet 3 Filed April 19, 1959 NOW R H U J M w. N R m T A July 8, 1941. A, J, BU CH 2,248,566

TELEPHONE SYSTEM Filed April 19, 1939 14 Sheets-Sheet 4 L W il ATTORNEY July 8, 1941. A. J. BuscH TELEPHONE SYSTEM 14 Sheets-Sheet 5 Filed April 19, 1939 IN VE N TOP A. J. BUSCl-l A TTORNE V July 8, 1941. BUSCH 2,248,566

TELEPHONE SYSTEM Filed April 19, 1939 l4 Sheets-Sheet 6 IN [/5 N TOR aam A 7' TORNE V July 8, 1941. BU H 2,248,566

TELEPHONE SYSTEM Filed April 19, 1939 14 Sheets-Sheet v //v VENT 4. J. BUSCl-l 51 ATTORNEY July 8, 1941. A. J. BUSCH TELEPHONE SYSTEM Filed April 19, 1939 14 Sheets-Sheet 8 lA/l/E'NTOI? By A.J.BUSC/-/ 6913 M .5316 L 6528 1:96 mn ISSUE-U A JOEFZOU UH? \Nk WNK kNk ATTORNEY y 1941- A. J. BuscH 2,248,566 TELEPHONE SYSTEM Filed April 19, 1939 14 Sheets-Sheet 9 51L con-ram. cmcurr z" CONTROL cmcurr A T TORNE V July 8, 1941. A. J. BUSCH TELEPHQNESYSTEM Filed April 19, 1939 .14 Sheets-Sheet 1O lNVENTO/Q A. J. BUSCH ATTORNEY July 8, 1941. sc 2,248,566

TELEPHONE SYSTEM Filed April 19,1939 14 Sheets-Sheet 11 INI/ A.J.BU$CH r ATTORNEY 14 Sheets- Sheet 12 Filed April 19, 1959 SNx 23 INVENTOR A J. BUSC H A TTORNEV Jul 's, 1941. J, BUSCH. 2,248,566

TELEPHONE SYSTEM Filed April 19, 1939 l4 Sheets-Sheet l3 INVENTOR A J. BUSCH A TTORNE V July 8, 1941.

FIG. /4

A. J. BUSCH TELEPHONE SYSTEM Filed April 19, 1959 14 Sheets-Sheet 14 /N l EN 70/? y AJ. BUSCH ATTORNEY Patented July 8, 1941 NT FFICE 'rELErnoNn SYSTEM Application April 19, 1939, Serial No. 268,651

12 Claims.

This invention relates to telephone systems and more particularly to systems in which automatic switching equipment is employed for establishing connections.

- It has been the practice heretofore in automatic telephone systems to provide a plurality of coin-control mechanisms at the central ofiice common to the coin district trunks in the centralomce, any one of which may be seized over an idle link circuit by a trunk having a call thereon established from a coin box substation, fora brief interval near the end of each period of conversation and an idle one of which may be seized for a brief interval at the end of each such period. When the control mechanism isv connected to a trunk near the end of a conversational period, it proceeds to collect the coin that was previously deposited at the calling substation in payment for the conversational period. At this time the control mechanism also transmits a warning tone to the calling subscriber advising him that the conversational period is about to expire and that he should deposit an additional coin if he wishes to continue the conversation. On its subsequent connection to the trunk, namely, at the end of the full conversational period, the control mechanism makes a test to determine whether the calling subscriber has deposited an additional coin for the next conversational period. If the mechanism fails to find a deposited coin when it attempts to collect on its first association with the trunk near the end of the conversational period, a monitoring operator is signaled and she makes connection with the calling line by way of a jack which is individual to the control mechanism and challenges the calling subscriber requesting him todeposit a'coin. When he does so she immediately collects the coin and withdraws from the connection. If the coin-control mechanism fails to find a coin when it tests the line at the end of any conversational period, it signals the monitoring operator and she makes connection with the calling line and requests the calling subscriber to deposit the coin in payment for the next conversational period. When the subscriber deposits an additional coin or advises the operator that he has already done so, she withdraws from the connection.

The control mechanism is also arranged to make a retest of the calling line for the presence of a coin after the monitoring operator withdraws from the connection following her request that the calling subscriber deposit an additional coin for the next conversational period. If on the retest the control mechanism finds that a coin has been deposited, the mechanism is disconnected and returns to common use, but, if the retest shows that no coin is present in the coin box, the mechanism again signals the monitoring operator and she returns to the connection and requests the calling subscriber to deposit a coin. On each withdrawal of the monitoring operator, the control mechanism tests the line for the presence of the coin and will not retire from the connection until the test has been satisfied.

Since the monitoring operator obtains connection to any calling coin line by Way of jacks which are individual to the common control mechanism rather than by way of connecting circuits individual to the central office trunks, the operators positionsare concentrated.

The object of the present invention is to improve the service rendered by circuits of the character disclosed in the event that peak load conditions occur.

A feature of the present invention is the provision of a coin-control release circuit common to a plurality of coin-control mechanisms which functions to release all coin overtime calls which have been unanswered by a monitoring operator and tocancel the test for the presence of deposited coins on coin collect calls when all coincontrol mechanisms have become busy due to a peak load condition, whereby coin-control mechanisms will be made available for use for regular coin collect and coin return service.

A further feature is the provision whereby an alarm and a visible signal are operated when a coin district trunk is excessively delayed due to the fact that no link circuit is available for connecting such trunk to a coin-control mechanism to identify the delayed group of coin district trunks to a maintenance man.

These and other features of the invention will be described more fully in detail in the following description and will be set forth in the appended claims.

Referring to the drawings which accompany the detailed description:

Fig. 1 shows a district junctor circuit arranged to function with a coin-control circuit and connected conventionally with a coin box subscribers station by a line link and group control circuit consisting essentially of cross-bar switches;

Fig. 2 shows in abbreviated schematic form the connection of the district junctor of Fig. 1 to a district link frame and thence through an ofiice link frame to an outgoing trunk;

Fig. 3 shows in abbreviated form the termination of the trunk of Fig. 2 and its connection through the cross-bar switches of incoming link and line-link circuits to a called subscribers line;

Fig. 4 illustrates in abbreviated manner, the connection of the district junctor of Fig. 1 through a subscriber link and control circuit to a subscriber sender conventionally represented by a box;

Figs. 5, 6, '7 and 8 placed with Fig. 6 above Fig. 5, Fig. 7 to the right of Fig. 6 and Fig. 8 beneath Fig. 7, illustrate a link and control circuit whereby a connection between the district junctor circuit of Fig. 1 and the coin-control circuit of Figs. 9 to 12, inclusive, may be established, portions of other links and control circuits being disclosed in Fig. 8;

Figs. 9, 10, 11 and 12 placed with Fig. 10 beneath Fig. 9, Fig. 11 to the right of Fig. 9 and Fig. 12 beneath Fig. 11, illustrate a coin-control circuit, other coin-control circuits being schematically indicated by the boxes in Fig. 9;

Fig. 13 illustrates a coin-control release circuit in accordance with the present invention, common to a plurality of coin-control circuits;

Fig. 14 shows a link busy alarm circuit; and,

Fig. 15 is a diagram showing the manner in which the several figures of the drawings should be arranged to show the complete circuit.

General description The invention is illustrated in an automatic telephone system in which automatic switches of the cross-bar type are used as a medium for extending connections from subscribers lines over trunks to other subscribers lines. These cross-bar switching mechanisms are controlled by register senders at the central office which receive the designations of wanted lines from the calling subscribers dial and by decoder markers which are connectable to the sender for receiving information from the sender and which are connectable to the proper switch frame for the purpose of testing the outgoing trunk, for testing the connecting link and for operating the magnets of the cross-bar switches to establish the connection.

While the system disclosed is not limited to the use of cross-bar switches of any particular type, reference may be had to the patent to Reynolds 2,021,329, of November 19, 1935, for an understanding of the construction and operation of a switch suitable for use in such systems. Because of the complicated nature of these systems and since it is not necessary for an understanding of the invention that the system in all of its details be disclosed, much of the circuits and equipment has been eliminated in the present disclosure for the sake of simplicity and in the following description reference will be made to numerous operations which are not fully disclosed in all their details. Whenever such references occur it will be understood that the circuits and equipment so referred to are already known and in particular are disclosed and completely described in Carpenter Patent 2,093,117, granted September 14, 1937, and Carpenter application Serial No. 214,356, filed June 17, 1938.

The subscribers lines, such as line I00, are connected to verticals of the primary crossbar switches indicated conventionally by the apparatus of box l0! and thence extended through secondary switches such as switch I02 to district junctor circuits. The connections to the district junctor circuit are efiected by means of a line link and group control circuit and a subscriber sender link and control circuit. The circuit details (not shown) whereby these connections to the district junctor circuit are effected may be the same as in Carpenter Patent 2,093,117 and in Carpenter application Serial No. 214,356, above mentioned.

When the connection to the district junctor, which is one of a group of similar junctors (not shown) is established as above outlined, the subscriber sender 400 through a link circuit represented schematically by primary and secondary cross-bar switches 40| and 402, functions in connection with a marker circuit indicated by the box 200 to establish a connection to an outgoing trunk 206 in accordance with the office code dialed at the sailing station I03 and recorded by the sender 400. This connection is established through district frame cross-bar switches 20! and 202 and oflice frame switches 203 and 204.

When the outgoing trunk 206 is thus seized, a connection is established through an incoming link and connector circuit consisting of cross-bar switches 300 and 30l and line-link circuit consisting of cross-bar switches 302 and 303 to the line of the called subscriber 304. After the subscriber of station 304 answers, this condition is registered in the district junctor of Fig. 1.

The district junctor of Fig. 1 has common access to a group of coin-control circuits one of which is shown in Figs. 9 to 12, inclusive. The connection to a selected coin-control circuit is made by means of the link and control circuit of Figs. 5 to 8, inclusive, which consists essentially of primary and secondary cross-bar switches 10! and 102.

The district junctor circuit of Fig. 1 is arranged to summon the coin-control circuit of Figs. 9 to 12, inclusive when required as follows:

(a) To collect a coin after a completed connection immediately after the calling subscriber has disconnected;

(b) To collect a coin during conversation at the end of a predetermined interval;

(0) To return a coin after an incompleted connection immediately after the calling subscriber disconnects or on a free call;

(d) To test for the presence of an additional coin at the beginning of an overtime period and in case no coin is found to summon an operator for overtime monitoring on the connection.

In the case of condition (a) the coin-control circuit makes a test to determine the presence or non-presence of a coin in the coin box I04 and to determine whether or not the coin box N34 has been properly cleared after the application of coin collect current. For either of these conditions lamp H00 is flashed to inform an operator of the failure to collect the coin. For condition (12) should the coin-control circuit fail to find the coin, lamp I IN is immediately flashed to inform the operator of this condition. For condition (c) lamp H00 is lighted steadily if the coin box is not properlycleared after the application of coin return current. For condition (d) the operator is summoned by the steady lighting of lamp I l0l if the test indicates that no coin is present.

In the event of a peak load causing all coincontrol circuits to become busy thereby indicating that no coin-control circuit is then available for the use of another district junctor, a chain circuit is closed over contacts of relays 800, etc., individual to the link control cir cuits to start the coin-control release circuit of Fig. 13 which is first effective to operate a multicontact relay, such as i300, to close loop circuits to all of the coin-control circuits and to operate other rnulticontact relays, such as I30I, to ground other conductors extending to coincontrol circuits. The rel-ease circuit then proceeds to measure a time interval of 60 to 90' seconds. If during this time interval any one of the coin-control circuits has been seized on an overtime call, and its overtime relay I000 is thus operated, it will be immediately released provided the coin-control circuit is still awaiting the response of a monitoring operator. It is assumed that at the expiration of this time interval, the peak load condition of all coincontrol circuits being busy .will have passed or be sufficiently relieved so that upon the release of the multicontact relay I300, the coin-control circuit may again serve coin overtime traffic.

Following the measurement of this time interval, a further interval of 6 to 8 minutes is measured, during which the multicontact relays 533! are maintained operated. During this interval the operation of the coin-collect relay IOI of any coin-control circuit will cause the operation of the no-coin test relay I002 of such coincontrol circuit on all coin collect calls to cancel the test for a deposited coin whereby the coincontroi circuit will be released immediately following the application of coin collect current without Waiting to test for the presence of a coin or to signal the operator in the event no coin has been deposited. If at any time during the latter interval, a peak load condition again occurs and all coin-control circuits become busy, the coin-control release circuit is arranged to start another coin-control release interval.

Detaiied description of operation The operation of the system will now be described in detail and for this purpose let it be assumed that the calling subscriber of station 03 initiates a call by depositing a coin I in the coin box set and by removing the receiver from the switchhook of the substation equipment of station W3. A circuit is thereby closed' for operating relay I56 which c'ircuit may be traced from, battery through the winding of relay I06, lowermost contact of cross-bar switch hold magnet 58?, over the ring conductor of line I00 through the switchhook contacts of station 103 and the winding and associated contacts H58 of coin collect magnet IE8 to ground at I09. Line relay I08 functions in cooperation with the line link and group control circuit of Fig. 1, the subscriber sender link and control circuit and subscriber sender circuits of Fig. 4 to effect the selection of an idle district junctcr circuit, of an idle line link extending thereto and of the circuit closure of said link. The idle condition of the district ,iunctor circuit is indicated by the presence'of battery on busy test conductor H3. The circuit details whereby this is accomplished are shown in the aforementioned application of W. W. Carpenter Serial No. 214,356, filed June 1?, 1938.

The selection before stated having been made, cross-bar switch contacts of the primary switch Ii)! and of the secondary switch I02 are closed extending the conductors of line I00 to conductors I it] and Iii which terminate respectively on the upper outermost and lower innermost back contacts of relay H2 through which contacts connection is made over conductors I I4 and -II5, through the cross-bar switch contacts of the sender link and control circuit represented diagrammatically by boxes 40I and 402, to subscriber sender 400. Dial tone is now furnished over these conductors as an indication to the subscriber at station I03 that dialing may be started. Ground is also connected at this time by the hold magnet 404 of the sender link and control circuit to conductor IIB whereby relay III is operated over a circuit which may be traced from battery through the winding of relay II'I, next to upper innermost back contact of relay NZ to ground on conductor H6. Relay I l! upon operating performs no useful function at this time except to disconnect busy test battery H8. from test conductor H3, this circuit being traced from battery I I8 through resistance H9, upper outer back contacts of relays I20 and I2I, lower back contact of relay II'I, lower back contact of relay I2l, inner lower back contact of relay ,I'I2,,upper back contact of relay I36 to conductor II 3. This disconnection of battery H8 makes the district junctor test busy to the sender link and control circuit on subsequent calls. Hold magnet 03 of the sender link and control circuit also connects ground to conductor I22 which is extended through the upper outer back contact of relay I23 through resistance I24 to sleeve conductor H25 thereby supplying holding ground for the line-link hold magnets I 01 and I26 while the sender 400 is connected to the district junctor circuit.

While the connection is being established from the calling line I00 to the sender circuit 400, the subscribers sender link and control circuit of Fig. 4 is momentarily connected to sender circuit 400 and during this interval, sender circuit 400 is furnished with the class of service information of line E00 and is also informed of the number of the district link and connector frames associated with the district junctor circuit to which the sender 400 is connected. The line link and group control circuit and the subscriber sender link and control circuit are used only momentarily to connect line I 00 to an idle district junctor circuit and to a subscriber sender circuit and are then released to serve other calls but the connections through the cross-bar switches IOI, I02, 40I and 402 which these circuits have established are held by the sender circuit 400 under the control of the calling subscriber. After the ofiice code has been dialed, sender 4G0 connects to the originating marker 200 by means of a connector circuit 405 over a group of conductors represented by the broken line 400. The sender circuit-400 registers in the marker circuit 280, the office code, the class of service information of the calling line I00 and the number of the district link and connector frame serving the district junctor circuit involved in the call, The marker 200 then furnishes the sender 490 with the necessary information which it requires to control the progress of the call. Marker 250 then selects an ofiice link and connector frame on which the desired trunk 206 leading to the called destination appears, connects itself thereto and also to the district link and connector frame that is associated with the district junctor circuit involved in the call. After this has been successfully done marker 200 connects ground to a conductor which is extended through connector 405, sender 400 and the sender link circuit consisting of switches MI and 402 to conductor I13, thereby operating district junctor relay I 21. Relay I21 upon operating connects ground over its upper middle contact to conductor I28 thereby operating select magnet 205 of the primary switch ZUI of the district link and connector frame serving the district junctor of Fig. 1 and connects ground over its inner lower contact to conductor I3I thereby operating relay 201 which is common to a group of district junctors served by the primary switch represented by box I. The operation of relay 201 extends conductors I29, I30, I3I, I32 and 209 through contacts of a marker connector relay to the marker circuit 200 selected for handling the call being established. This connector relay (not shown) being indicated only by the broken lines is individual to the marker circuit 200 and is operated each time that marker 200 is selected for service in establishing a connection to the district frame represented by Fig. 2. Conductor I29 is used by marker 200 to determine when the primary switch 20I has operated, from ground supplied by the marker over conductor 209. This is effected by the extension of the aforesaid ground through the lowermost primary switch contact associated with magnet 208 over conductor I14 through the uppermost front contact of relay I21 over conductor IE9 through the next to upper contact of relay and a contact of the aforesaid marker connector relay (not shown) to marker 200. Conductor I30 is grounded by marker 200 and is extended through the next to inner upper contact of relay 201 and the upper innermost front contact of relay I21 to operate relay I33 for calls to an operator. Conductor I3I is used by the marker 230 to hold relay I21 operated through its lower innermost contact until the marker 200 releases as hereinafter described and conductor I32 is extended over the inner upper contact of relay 201 and through the lower contacts of relay I21 and conductor I to give the sender 400 a trouble release signal if a trouble condition has been encountered by marker 200 in establishing the connection. If the relay I33 is operated, it will lock through its lower inner contact to ground supplied by the sender 400 over conductor I34.

Marker 200 now establishes the connection through the district and office switches to trunk 206. Select magnet 2"] of secondary district switch 202 is operated by ground on the lower contacts of relay 201. Select magnet 2I2 of the primary office switch 203 is operated by ground on the upper contact of relay 2 I3 and select magnet 2I4 of the secondary switch 204 by ground on the contacts of relay 2 I5, both of which relays are operated by marker 200.

is established when relay 2I9 is operated by The link between V the secondary district and primary office switches marker 200 and operates hold magnets 2H and 2I1 from ground over conductor 2I6. The link between the primary and secondary switches of the office frame is completed when hold magnet 2I8 is operated from ground in the marker over the lower contacts of relay 2I3.

After the marker 200 has established connection with the trunk 206 as before described, it releases relay I21 by removing ground from the winding of relay 201. Relay I21 releases and closes the sleeve conductor I14 to the ground on the inner upper front contact of relay I I1. Marker 200 tests for this ground and if it finds it, disconnects. Relay I I1 was operated over conductor I10 when the sender link and control circuit connected sender 400 to the district junctor of Fig. 1. Relay I21 upon releasing opens conductors I20, I29, I30, I3I and I32 extending to the district link and connector circuit and connects conductor I35 over its lower back contact to the winding of relay I33 so that the sender may later operate this relay. When the marker has established connection to the outgoing trunk 206, sender 400 then cooperates with the incoming apparatus of Fig. 3 to complete the connection to the line of the called subscriber 304. In connection with this incoming apparatus, a terminating sender and terminating marker (not shown in Fig. 3) are provided. As soon as the connection to trunk 206 is established, a circuit is closed for operating relay 305 over back contacts of relay 300, conductors I38 and I40 to conductors I44 and I45 extending into the subscribers sender 400. The operation of relay 305 at first closes a start lead (not shown) that causes the terminating sender aforesaid to be connected. After this the terminating sender receives from the sender 400 the necessary information for completing in cooperation with the aforesaid terminating marker the connection to the line of the called subscriber 304.

After the sender 400 has completed its func tion in establishing the connection as above outlined, it connects ground to conductor I35 to operate relay I36 over the lowermost back contact of relay I21. When relay I36 operates, it looks under control of relay I12 in a circuit from battery through its winding and the inner upper back contact of relay I12 to ground over the next to inner upper front contact of relay I36. Relay I36, in operating, closes the talking circuit to station I03. This may be traced from conductor IIO over the uppermost back contact of relay H2, next to uppermost front contact of relay I36, next to upper back contact of relay I12, condenser I31, lower middle front contact of relay I36 and outer lower back contact of relay I12 to conductor I38; also from conductor III, over the inner lower back contact of relay I I2, next to inner lower front contact of relay I36, middle lower back contact of relay I12, condenser I39, upper front contact of relay I30 and upper back contact of relay I12 to conductor I40. Relay I36 also closes a holding circuit for relay I33, if this relay has been previously operated by the marker 200 for an operator class of call, and furnishes talking battery through the windings of relay I4I to line I00. For this purpose ground is supplied through the left winding of relay I4I, next to inner upper back contact of relay I I2 to junction point I42 and battery is supplied through the right winding of relay I4I, next to inner lower back contact of relay II2, to junction point I43.

After the sender 400 has completed its functions and has operated relay I36 over conductor I35 as before stated, it releases. This causes cross-bar switches 40I and 402 of the sender link circuit of Fig. 4 to be released which opens the connection to conductors H4, H5, I34, I22, I13, I44, I45 and I35. The established connection is now placed under control of the district junctor circuit of Fig. 1 and is held under the control of relay II1 which remains operated provided the calling subscribers receiver is off the switchhook at station I03 and relay MI is thus maintained operated over the line loop. Relay I4I holds relay I I1 operated over a circuit that may be traced from ground over the upper front contact of relay 1, contacts of relay I4I, next to inner upper back contact of relay I12, through the winding of relay II1 to battery.

After the connection to the trunk 206 has been by the automatic release circuit; (g) connects ground over its next to inner lower frontv contact established a circuit is completed for operating the bridged impedance relay 305 of the incoming trunk circuit over the loop extending to the calling district junctor circuit of Fig. 1 which may be traced through the windings of relay 305, upper and lower back contacts of the reversing relay 306 over trunk 206, contacts of cross-bar switches 204, 203, 202 and I over conductors I40 and I38, outermost back contacts of relay I12, upper and lower middle front contacts of relay I36, winding of polarized relay I46 and retardation coil I41 and the inner lower front contact of relay I I1. Relay 305 operates in this circuit, but polarized relay I46 does not operate at this time.

When the called subscriber at station 304 answers, a circuit is established for operating bridged impedance relay 301 which may be traced from battery and ground through the windings thereof over the tip and ring talking conductors and contacts of cross-bar switches 300 and I of the incoming link circuit and the cross-bar switches 302 and 303 of the line link circuit to the line leading to the called station 304. Relay 30'! upon operating closes an obvious circuit for reversing relay 306 which, upon operating, reverses battery and ground over trunk 206 thereby causing polarized relay I46 of the junctor circuit of Fig. 1 to operate. Relay I46 upon operating connects ground to the armature of interrupter I through the inner upper back contact of relay I33. When thereafter the interrupter I48 connects ground through the lower winding of relay I23, relay I23 operates and locks to the operating ground through its lower inner front 1 contact. After a predetermined short interval, say two seconds, interrupter I48 closes a circuit for operating charge relay I49 over a circuit from battery through the winding of relay I49, outer lower back contacts of relays H2 and I50, offnormal contacts I69 of interrupter cam I5I upper back contact of relay I50, next to inner upper back contact of relay I2I upper inner contact of relay I23 through the right contact of interrupter I48 to ground on its armature. Interrupter I48 1.

thus insures against the possibility of that charge relay I49 might operate on a momentary line closure and thereby cause the deposited coin at station I03 to be improperly collected.

Relay I49, upon operating, (a) locks under control of relay H2 in a circuit from battery through the winding of relay I49, lower back contact of relay I I2 to ground on the lower front contact of relay I49; (b) partially prepares a path for starting an automatic release circuit to be hereinafter described by connecting the back contact of polarized relay I 46 over its uppermost contact to interrupter I54; (0) partially prepares a path for operating relay IE2 by connecting the winding of relay II2 over its next to inner upper contact and the lower back contact of relay I23 to the upper contact of relay I55; (11) provides an auxiliary holding circuit for relay I36 which is required when the automatic release circuit arrangement releases the district junctor circuit by operating relay I12, this holding circuit extending from battery through the winding of relay I36, lower back contact of relay I 21 to ground over the upper middle contact of relay I49; (e) partially closes to conductor I51 to be used later by the coinpontrol circuit as a signal to collect the coin deposited in the coin box I04; and (h) closessa circuit for operating the magnet I50 to start. timing the call. This circuit may be traced from i battery through the winding of magnet I50, next to outer lower front contact of relay I l9,.inn'er upper back contact of relay H2 to ground on: the upper front contact of relay 1. i

It is now in order to describe the operatic whereby a coin deposited in coin box I04 is col-h lected or returned or an operator is summoned to monitor, on an overtime call or in responseto a failure of the calling subscriber to deposit. the coin or in response to a stuck coin condition.

The collection of the deposited coin due to the disconnection of the calling party, prior tot-he expiration of the time allowed for a conversational period will now be discussed. When the calling subscriber at station I03 disconnects, re-- lay I4I releases which in turn releasesyrelay ill. Relay relay Ill releases. When relay II'I releases, .it causes relay I20 to operate in a circuit which may be traced from ground through the lower: winding of relay I20, upper middle front contact. :of relay I36, next to upper front contact of charge relay I49, lower back contact of relay I2I,

lower back contact of relay I ll, upper back con-' tact of relay I2I, next to-lower front contact of relay I36, inner upper back contact of relay I2I-,: to battery through resistance I59. Relay-J20 operated, looks over its inner lower front contact and the inner upper back contact of relay; I2I to battery through resistance I59; connects ground over its lower middle front contact tothe middle lower back contact of relay I2! to start conductor I60 to cause a coin-control circuit to be connected to the district junctor .circuit, and furnishes a holding circuit for relay I36 extending from ground over the lower front con-tact of relay I20, the upper back contact of relay I23 and the inner upper front c-ontactand winding of relay I36 to battery.

When ground is connected to start conductor I60 as aforesaid, the link and control circuit of Figs. 5 to 8, inclusive, functions to cause an idle coin-control circuit SlllCh as is disclosed in Figs. 9 to 12, inclusive, to be connected to the district junctor of Fig. 1. The district junctors are divided into groups of ten, one half of which groups have norm-a1 access through an A group of link circuits and the other half of which groups have normal access through aB group of link circuits to a plurality of coin-control cir-- cuits. A link control circuit is provided common to the A links and a similar control circuit is provided common to the B links, each control 'circuit being provided with ten group relays 500 to 509, inclusive, corresponding to the-ten groups of district junctors having access to t e links controlled thereby and each group of ten district junctors is provided with a group of relays such as 600 to 603, inclusive. For the sake of clarity only one of the link circuits, one of the two control circuits and the group relays of one district junctor group have beendisclosed.

Upon the connection of ground to conductor I60, assuming that the district junctor is in the tenth subgroup having normal access to a link circuit of the A group and assuming that there is apath available over the. link disclosedto a I46 releases, releasing relay I23, ;when the called subscriber disconnects or when:

coin-control circuit, a circuit is established for the No. 9 group relay'509 which may be traced from conductor I60 over a back contact of relay 600, conductor 605, back contact of the hold magnet 103 of the primary link switch 10!, upper back contact of relay 1'04, conductor 105, back contact of relay 60I, upper back contact of relay 606, conductor 60?, winding of relay 509, individual to the calling junctor subgroup, to battery. On calls from other junctor subgroups, similar circuits would be extended to the windings of other group relays such as 500 and 504 individual to such groups. The relays 500 to 509, inclusive, are arranged in a chain so that when simultaneous calls from dilferent subgroups of junctors are received only that group relay is effective which corresponds to the lowest numbered group of junctors in the order of preference.

idle, and that group relay 509 is the only group relay operated, the following circuits are established: (a) from ground through the winding of relay 602, upper front contact of relay 509 and upper back contacts of other group relays such as 504 and 500, conductor 5| I, No. 8 back contact of relay 609 through resistance M to battery; (b) from battery through the winding of relay 606, conductor 608, to ground at the lower front contact of relay 500; (c) from battery through the winding of relay 6H, upper back contact of relay 6I2, No. 4 back contact of relay 609, conductor 6| 3 to'ground at the middle lower front contact of relay 509 and (d) at its upper back contact opens the circuit of relay 5I0 which releases to apply ground to conductor M2 for starting a timing operation. With relay 602 operated, a locking circuit is established for relay 509 which may be traced from battery through its winding and inner lower front contact, conductor 5l3, lower front contacts of relay 602, conductor 5| 4, inner upper front contact of relay 509 and over the inner upper back contacts of other relays such as 504 and 500 to round.

Relay 606 upon operating opens the operating circuits of relays 500-509, and with relay 602 operated as described, closes a circuit for operating relay 600, extending from ground over its next to lower front contact, the inner upper front contact of relay 602 to battery through the winding of relay 600. Relay 600, upon operating operates relay 603 in a circuit from battery through its winding, the upperfront contact of relay 602 to ground at the front contact of relay 600 and individualizes the start conductors such as I60 of the subgroup of junctors in which the calling junctor is located so that they become available for identifying the junctor which is calling. With relay 603 operated, the start conductors from the calling subgroup of junctors are extended to the operating windings of relays H0 to H9, inclusive and assuming that the district junctor of Fig. 1 is the first junctor of the subgroup, a circuit is effective for operating relay H0 extending from ground applied to the start conductor I60, No. 3 contact of relay 603, No. back contact of relay 6M, conductor 6I5, upper winding of relay H0 to battery. If there is more than one simultaneous call in the subgroup one or more of relays H0 to H9, inclusive, may 0perate. The operation of any one of these relays establishes a circuit for relay 6I2 extending from battery through the winding of relay BIZ, upper front contact of relay 6| I, conductor 6H5, lower It being assumed that both control circuits are front contacts of operated relays H0 to H9, inclusive, conductor 6", No. 6 back contact of relay 609, No. 2 front contact of relay 603, conductor 605, thence as traced to conductor I05, lower front contact of relay 002, conductor 5M, inner upper front contact of relay 509, and over the inner upper back contacts of other group relays including relays 505 and 500 to ground. Relay 6l2 locks over its upper front contact to the operating circuit just traced independent of relay 6| I; at its upper back contact opens the operating circuit of relay 6H which starts to release and at its inner lower front contact prepares a locking circuit for an operated relay of the groups H0 to H9, inclusive, and an operating circuit for relay 6M as later described.

With the link circuit disclosed idle, as assumed, relay 593 upon operating establishes a circuit from ground over the lower back contact of hold magnet I06 of the primary link switch l'fll, conductor 50?, No. 14 contact of relay 603, conductor 646, lower back contact of relay 5I5, winding of relay 5| 6 to battery. If relay 002 is not operated, indicating that the first group of five coin-control circuits in which the control circuit disclosed in Figs. 9 to 12, inclusive, is located, is not being held by another link and control circuit and two or more coincontrol circuits of the group are idle, a circuit will be established upon the operation of relay 5l6 extending from battery through the upper winding of relay 823, conductor 808, lower back contact of relay T04, conductor I08, contact of relay 5I6, lower back contact of relay 5I'l, conductor sat; next to lower back contact of relay 802, upper back contact of relay 89I and to ground over chain contacts controlled by the coin-control circuit busy relays 805 to 801, inclusive of the group. Similar test circuits are established by the operation of relay 5I6 or of relay 5I9 to determine if there are two or more idle coin-control circuits in the three other groups to which the link circuits have access and if such idle control circuits are found, the corresponding coin-control circuit group relays 824 to 326 will also be operated.

It will be recalled that upon the operation of relay 6I2, slow-to-release relay 6II started to release. As soon as relay 6 is fully released and closes its back contact, a circuit is thereupon established for relay 5H extending from battery through the winding of relay 5I1, conductor 520, back contact of relay GM to ground at the inner upper front contact of relay 6l2. If any group of coin-control circuits is not being held busy by another link and control circuit or if the coin-control group busy relay 86! is not operated, the corresponding group relays 823 to 026 will be operated. For example, the relay 623 will be operated in a circuit from battery through its upper winding, thence as traced over the front contact of relay 516, middle lower front contact of relay 5I'I, conductor 52I, outer lower back contact of relay 802 to ground at the inner upper back contact of relay L When one or more of the group relays 023 to 826, inclusive, have operated on either the first or second test, a circuit is closed for operating one of relays 609 to 8H individual respectively to the several link and control circuits. In the present instance relay 809 will be operated in a circuit extending from ground through its winding, lower front contact of group relay 823, conductor BIZ, No. 1 front contact of relay 603, lower front contact of relay 6I2, No. 9 back contact

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