US2277600A

US2277600A - Telephone system

Info

Publication number: US2277600A
Application number: US312468A
Authority: US
Inventors: James B Mckim
Original assignee: Bell Telephone Laboratories Inc
Current assignee: AT&T Corp
Priority date: 1940-01-05
Filing date: 1940-01-05
Publication date: 1942-03-24
Anticipated expiration: 1959-03-24
Also published as: NL70955C; USRE22476E; GB644112A; FR959818A

Description

March 24, 1942. .1 B, MCKIM 2,277,600

TELEPHONE SYSTEM Filed Jan. 5, 1940 11 Sheets-Sheet 1 ATTORNEY March 24, 1942.y J B MGKIM 2,277,600

' TELEPHONE 'SYSTEM Filed Jan. 5, 1940 11 sheets-sheet 2 OUTGGING TRUNK MARKER /N VEA/TOR By J. B. Mc KIM ATTORNEY March 24, 1942. J, B, McK|M 2,277,600

TELEPHONE SYSTEM Filed Jan. 5, 1940 11 Sheets-Sheet 3 il' N 1 1' AT TORNE Y March 24, 1942.

SE C OND CHANNEL J. B. MCKIM TELEPHONE SYSTEM Filed Jan; 5J, 1940 11 Sheets-Sheet 4 /N VEN TOR I J5. Mc K/M "W KM@ ATTORNEY 'March 24, 1942. 1 B. McKlM 2,277,600

TELEPHONE SYSTEM Filed Jan. A5, 1940 11 sheets-sheet 5 /N VEA/ron J. B. Mc K/M ATTORNEY March 24, 1942. J. B. MMM 2,277,500

TELEPHONE SYSTEM Filed Jan. 5, 1940 11 shets-,shee't 6 TEST/N6 CIRCUIT TRUNK GROUP AFFARI TUJ` /NVENTOR JB. MC K/M awww@ A T TORNV March 24, 1942.

J. E3.lWC| |hd TELEPHONE SYSTEM Filed Jan. 5, 1940 11 Sheets-Sheet 7 /NVENTOR y J B. Mc K/M March 24, 1942. J. B. McKlM v 2,277,600 v TELEPHONE SYSTEM Filed Jan. 5, 1940 1l Sheets-Sheet 8 //v VEA/Tok J. B. Mc KIM BV www( March 24, 1942.

J. B. MCKIM TELEPHONE SYSTEM Filed Jan. 5, 194C 11 Sheets-Sheet 9 /NvE/voR J. B. Mc KIM BY web ATTORNEY -March 24, 1942. J, B,A McklM 2,277,600

TELEPHONE SYSTEM Filed Jan. 5, 1940 f 11 Sheets-Sheet 10 nwe/v TOR J B. MC K/M A 7' TORNE V March 24, 1942.` Bl, McKlM TELEPHONE SYSTEM Filed Jan. 5, 1940 11 sheets-sheet 11 /NVEN TOR JB. MC K/M BV www W A TTORNE V Patented Mar. 24, 1942 gruttoy UNITED STATESATENT OFFICE TELEPHONE SYSTEM James. B. McKim, Newv York,y N. Y., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application January 5, 1940, Serial No. 312,468 v l0 Claims. (Cl. 179-27) This invention relates to telephone systems and more particularly to switching systems for automatically connecting units of equipment together for telephone connections and supervision.

Switching systems which are automatically responsive to incoming telephone calls have included link structures for connecting units of equipment together which serve either as transmission paths or for setting equipment for completing a telephone connection. Links used for transmission paths for telephone connections are held in place for the duration of the telephone connection. Other links used for temporarily connecting units of equipment together have been released' after the connected equipments have completed their functions in setting switches or other units of equipment for completing a telephone connection. In the latter method of operation it is often necessary to recall the services of the same link or a link of like structure in the same group of links one or more times for supervisory purposes after a telephone connection has been completed. The selection and operation of links for supervisory purposes constitute a delay in the continuity of telephone service which with the present invention may be avoided.`

An object of this invention is, therefore, t0 provide channels including a link between the equipments involved in a telephone connection and an operators position, which may be automatically or manually locked for supervision of particular classes of telephone connections and automatically or manually released when the class of the telephone connection requires no supervision from this operators position.

A feature of this invention is in a system of selecting and operating an idle link responsive to an incoming call over a trunk line for connecting the trunk line to a channel in an operators position, in connecting the incoming trunk line to an outgoing trunk line and in controlling the locking or releasing of the link and channel responsive to signals registering the class of the incoming and the outgoing trunk lines involved in the telephone connections. i

Another and related feature of this invention is in a system of selecting and operating an idle link responsive to an incoming call over a trunk line for connecting the trunk line to a channel in an operators position, in transmitting signals between the trunk line and the position channel, in setting a control unit from the operators position for automatically completing a telephone connection and in automatically controlling the locking or releasing of the link and channel ref sponsive to the signals registered in the control unit.

Another and related feature'is in a system yof automatically controlling the locking or releasing of the link and channel by transmitting class signals from the trunk line to the control unit, responsive to the connection of the link to the position channel and responsive to the connection of the control unit to the position circuit.

Another and related feature is a'system for manually controlling the locking of the link and channel to the trunk line connection for the duration ofthe call or releasing the link and channel therefrom.

These and other features will be discussed more fully in the following description.

To illustratethe features of the invention reference may be ,hadto the accompanying drawings in which:

1 Figs. 1 toV 11, inclusive, when arranged as indicated in Fig. 12 show the detailed structure in which a link' and channel may be'locked to the apparatus involved in a telephone connection for supervisory purposes ;y

v Figs. land 2 illustrate a distant calling toll oflice, an incoming trunk, an outgoing trunk, a

`alternating current signals.

plurality of switches for connecting incoming and= outgoing trunks and a distant called toll office; l

Fig. 3 illustrates a link and a connector for rconnecting calling incoming trunks and link switchesA to aflink-control circuit shown in Fig. 6; f Fig. 4 illustrates the operators positionchannels;

, Figs, 7, 10 and 11 illustrate a cordless toll operators position circuit;

, Figs. 5 and 8 illustrate a cordless toll position control circuit;

Fig. 9 diagrammatically illustrates an operators position sender, a connector for connecting such sendersto one of a plurality of markers and the apparatus of a marker which may be used to disclose the invention.

GENERAL DEscRIeTioN The trunks incoming to a toll office vary in transmission characteristics and also vary in character. Via or terminal ringdom trunks incoming from a distant toll ofce operate from a Other toll offices may use the straightforward trunking system transmitting direct current signals for energizing the incoming ktrunks of a distant office. Other trunks are known as dial intertoll trunks which are operated from pulse transmitting systems for automatically operating apparatus in a machine switching office. In view of this the trunks involved in a toll connection require different class of service signaling means depending upon the character of the trunk. Signal transmitting apparatus is included in each such trunk for indicating to the associated apparatus of an automatically operable toll office, the character ofthe trunk connected to this apparatus in order that the same character of trunks shall or shall not be connected together for transmission purposes, and in order that it shall be determined whether supervision of the telephone connection is required. The same or diierent characters of intertoll trunks are connected together depending upon the length of the interconnected toll trunks for completing a telephone connection. It is therefore necessary that the connecting apparatus be guided in the matter of class of intertoll trunk and the transmission characteristics of both interconnected trunks. In the system disclosed, such information is automatically available responsive to the connection of an incoming trunk with the connecting apparatus and responsive to the registrations for selecting an outgoing trunk to a local or distant office.

A call from a distant oflice actuates the apparatus of the receiving toll oiiice by signals, which automatically energize the apparatus of a link for connecting the intertoll trunk such as disclosed in Figs. 1 and 2 with a cordless toll operators position, such as disclosed in Figs. '7, 10 and 11. An idle link channel is chosen by the energization of the link-control circuit of Fig. 6 which selects an idle channel, Fig. 4, entering one of a plurality of cordless toll operators positions. There are ordinarily a plurality of channels entering each position. Each channel is connected to a secondary link switch, such as

switches

302 or 303. These are interconnected to a plurality of primary link switches available to the calling incoming trunks. By means of cross-wiring these secondary switches may be associated through one of a plurality of primary switches with the calling incoming trunk thus an idle channel of a position may be actuated by the link-control circuit, Fig. 6, and connected by this link-control circuit through a secondary and primary link switch which are also actuated by the link-control circuit. The operation of the link switches connects the apparatus of the channel with the apparatus of the calling incoming trunk circuit causing the energization of apparatus in both the channel circuit and the calling incoming trunk circuit. The energization of this apparatus is successively interacting which adjusts the incoming intertoll trunk circuit, Figs. 1 and 2, and adjusts the apparatus of the channel, Fig. 4, and the position apparatus, Figs. "I, l and l1, for successive cooperative signals. The apparatus of the channel and position circuit is adjusted for receiving class of trunk line signals from the incoming trunk circuit. The incoming trunk circuit is adjusted for transmitting these signals. The operation of the position apparatus progresses to a point where signals are given to the cordless toll operator including a tone signal to indicate to this operator the character of call to be answered.

The apparatus of the position control circuit, Figs. and 8, is energized including a start circuit for the sender 900. Registrations are made in the sender by the cordless toll operator according to code designations given to her by the Acalling party at station 00. The sender energizes a marker connector for associating an idle marker therewith which receives code registrations from the sender covering the distant toll office or station to which the call should be routed, the character of the trunk lines, the class of the call and the character and class of the incoming trunk line. The registrations are used for selecting an outgoing trunk of a particular routing having the characteristics required for the type line connection to be made.

Circuit combinations are made in the marker by apparatus operated in accordance with the foregoing registrations which control operations in the sender and the position control circuit when the marker is in the process of releasing. The circuits energized determine whether a link and channel is to be connected between the incoming trunk and position channel apparatus for the duration of the telephone conversation or whether this apparatus shall be released. When supervision is to be maintained over a telephone connection during the period of conversation, circuits are established in the position control circuit for energizing a particular relay in the incoming trunk circuit. The energization of the latter relay establishes a locking path for the link and a locking path for particular apparatus in one channel of the position which is associated with this link connection. The position channel and the link is thus locked for maintaining supervision of the telephone connection. Energization 0f apparatus in the position control circuit by a circuit combination in the marker also energizes a. relay in the incoming trunk when no supervision is required. In this case the channel and link switches are released and may be associated with other incoming trunks for serving other incoming calls. When the link is locked to a channel, only one relay in the channel is kept operated for associating signal paths between the position and the incoming trunk circuit so that the toll operators position signals may be actuated at any time when either the calling or called parties require the attention of the cordless toll operator.

In addition to the arrangement for locking a link and channel automatically from the marker, a second arrangement is used for locking the link and channel manually by the energization of a position key which energizes relays accomplishing the result manually which is accomplished automatically by the marker. The actual locking of the link is only accomplished after the marker has completed the selection of the outgoing trunk and set the switches for the connection between this outgoing trunk and the incoming trunk. As before, the marker in the process of releasing energizes apparatus which completes circuits for locking the link by the energization of particular relays in the position control circuits. This manner of locking the link manually is placed under the control of the marker in order that apparatus operations take place in proper sequence.

DETAIL DESCRIPTION In the present disclosure the distant office |00 is connected to the automatically operable toll cnice illustrated in the drawings Figs. 1 to 1l, inclusive, by a ringdown intertoll trunk which is energized by transmitting ringing current from office |00 over conductors |35 and |36 to the incoming trunk, Figs. 1 and 2. After the distant operator in office |00 has completed setting apparatus for the connection, this ringing current is applied .automatically or manually to conductors |35 and |30 which is transmitted through the winding of alternating current relay |03 energizing this relay. The energization of relay |03 releases relay |04 which is normally energized from battery through its winding to ground on the contact of relay |03. The release of relay |04 establishes a circuit for operating the incoming trunk relay 202 over a circuit from battery through the winding of relay 202, contact 2 of relay |04, contact 1 of relay ||1, contact 6 of relay 203 to ground. Relay 202 in operating establishes a locking circuit for itself through its contact 3, contact 1 of relay ||1 to ground through contact 0 of relay 203. When ringing current is disengaged from the trunk conductors |35 and |36', relay |03 releases which reenergizes relay |04. A circuit is thus established for relay ||3 from battery through its winding, contact 5 of relay M2, contact 2 of relay |04, contact 3 of relay 202, contact 1 of relay |1, contact 0 of relay 203 to ground. Relay ||3 is locked through contact 4 of relay 20|, contact 5 of relay H3 to its operating ground on contact 6 of relay 203. The operation of relay ||3 now establishes a start circuit for a link which associated the incoming trunk and the operator at ofce |00 with the cordless operator Whose telephone apparatus is shown in Fig. 11 of this disclosure. This linkstart circuit may be traced from ground on contact of relay ||4 through contact 2 of relay H3, contact of relay ||2, lead 320, contact of relay 3|2, winding of link-start relay 3| i to battery. The link-connector and link-control circuit is shown diagrammatically and reference is made to the patent application to King et al. Serial No. 295,010, iiled September 15, 1939 issued as Patent No. 2,236,246, March 25, 1941 or Link connector The energization of the link-start relay 39| establishes an obvious circuit for a link-connector selecting relay 3|@ which operates a multicontact relay such as `3|1 for connecting a large number of leads from an idle link-control circuit, Fig. 6, to the incoming trunk circuit, Fig. l

Aand Fig. 2, to a plurality of toll positions, Fig. 4,

and to a plurality of switches, Fig. 3. There are a plurality of link-control circuits, Fig. 6, which are small compared to the large number of switches, Fig. 3, and the large number of position channels, Fig. 4. Consequently, as noted in the aforementioned patent applications, it is necessary for a link connector to nd an idle linkcontrol circuit before operating the multi'contact relay 3|1 to connect these different units together. The switches 300 and 30! represent a single horizontal level in two verticals of a primary link cross-bar switch connected to an incoming trunk circuit.

Switches

302 and 303 are known as secondary switches of which there are a large plurality connected to a largevplurality of channels in a plurality of cordless toll positions. The ones shown are diierent horizontal levels on diierent verticals of the same or different cross-bar switches. The function of the link-control circuit is to test a plurality of channels associated with a plurality of cordless toll positions to obtain an idle channel and the services of the toll operator in the cordless position to which this channel is connected. In view of the fact that each channel is connected to a different horizontal level of secondary switches, such a

's

302 and 303, the test of the channel determines the secondary switch to be used. Each incoming trunk appears on at least one horizontal level oi. a primary linkv switch which may be reached from different secondary link switches through diierent verticals on this primary link switch. The hold magnets for the primary and secondary switches, which constitute a channel, are connected in multiple as shown and operate together. An idle channel in a position having an operator in attendance has battery on lead 340 and ground on lead 34|. Ground is placed on lead 34| by the operation of relay 40|I actuated when relay 10| is actuated. Relay 10| is only actuated when an operator is servingv the cordless position. The circuit for relay 10| may, thus, be traced from battery through its winding, contact oi individual channel relays 42|, 420 and 402 normal,.jack H04 which has its contact closed when the telephone operators headset plug |00 is inserted therein, key 505, to ground on contact of relay 500. Relay 40| has as many contacts thereon as there are channels in the position and, therefore, its operation makes all channels idle which are not in use. The release of this relay makes all channels busy. This will be seen fromthe description of the channel apparatus.

Link and Zink-control circuit The link-control circuit, Fig. 6, is used for selecting an idle channel from a large plurality of channels entering cordless toll positions. The control circuit is associated with channels which are connected to certain levels of the secondary cross-bar switches shown in the right-hand portion of' Fig. 3. These control circuits are in an incoming group arranged to serve the calling incoming trunks for testing the channels of the position and operating switches which connect a calling incoming trunk with an idle channel. The operation of start relay 3|| establishes circuits for energizing a connector unit for controlling the association of'a calling incoming trunk with an idle link-control circuit. The switches 300 and 30| comprise a portion of a primary link switch. Each switch of vthis character ordinarily has ten separate levels and a large plurality of verticals. In this instance only one is shown which is arranged to connected the calling incoming trunk to a secondary switch by the operation of a select magnet and a hold magnet. In practice the incoming trunk may be associated with Various

secondary switches

302 and 303 through a number of different verticals on the primary switch, making a large plurality of choices of apparatus for extending a, call from the incoming trunk to the apparatus of the channels in the toll olice switchboard. The

secondary switches

302 and 303 may be on a single crossbar switch or on separate cross-bar switches depending upon the choice of connection which is best suited for use. The secondary switch points shown may thereforebe considered as one level of any vertical on a single cross-bar switch or one level of a vertical on any of a plurality of cross-bar switches.

The multicontact relay 3|3 and the multicontact relay 3|1 and the relays shown in the lower portion of Fig. Sconstitute an arrangement for giving an incoming trunk a plurality of choices,

in obtaining the services of a link-control circuit, Fig. 6, which may be associated therewith by the operation of the multicontact relay 311. The control circuit associated with a relay, such as 311, must test idle before it is seized. There are a plurality of multicontact relays 313 for each incoming trunk circuit. This plurality of relays are connected to a plurality of relays 311 which are interconnected when strapped as shown. There are a plurality of relays, such as 311, for each connector extending between the contacts of relays 313 and 31'1. Each control circuit has a representative relay in each connector so that any one of the control circuits may be associated when idle with any of the connectors between a group of trunks and the control circuits. The operation of start relay 311 by a circuit as previously established from the incoming trunk initiates the selection of an idle control circuit. -A circuit is first established from battery through resistance 310, contact of start relay 3| 1, winding of relay 316 to ground where a chain of relays, such as 316, is used to prevent the actuation of a connector by more than one trunk and for the selection of an idle control circuit. When the control circuits associated with such relays are busy no circuit is established for the relay. The energization of relay 316 establishes an operating circuit for the multicontact relay 311 for seizing an idle link-control circuit.

As previously stated the organization of the link switching arrangement and the control circuit is such that a choice is made from a large number of channels. In some instances a number of idle channels are simultaneously associated with the control circuit and only one of these is selected. The selection is made by a chain circuit in a secondary switch level selecting circuit 604 in which there are a plurality of relays equivalent to the number of channels which are tested. Relay 605 represents one channel. This relay, however, represents a switch combination associated with diiTerent channels, such as secondary switch 302 and primary switch 300 or secondary switch 302 and primary switch 301, each combination being associated with a difierent channel. In the same manner a plurality of verticals on the primary switch are connected to verticals on a plurality of secondary link switches. The verticals of the secondary link switches each have a plurality of horizontal levels connected to diierent position channels. The hold magnet on the vertical of the primary link switch and the hold magnet on a. vertical of a secondary link switch are in multiple so that they may be operated simultaneously. The operation of any of the relays 605 indicates that they are associated with an idle channel and the preferred idle channel in the chain of relays, such as 605, is taken for the connection. In practice there are as many contacts on relay 314 of the connector as channels which are connected to the control circuit, Fig. 6. These relays are operated for associating the channel equipment with the control circuit to energize apparatus of the control circuit for selecting the idle channel and for making a test of this idle channel through the contacts of relay 315. This latter test is actually a secondary or double test to make sure that the channel is not seized by another control circuit immediately after it has been found idle by the control circuit being described. The operation of any particular relay, such as 605, determines the secondary switch level to which the idle channel selected is connected and, consequently, the

control circuit may energize the switch combination of primary and secondary switches for connecting the incoming trunk to the channel selected.

A group of links and link-control circuits serve a plurality of groups of trunks which may be known as subgroups of trunks within the larger group. When a particular trunk within a subgroup of trunks actuates a link circuit, it is necessary to identify the subgroup with which it is associated. The link-control circuit is therefore provided with a plurality of relays 608 equivalent to the number of trunk subgroups served through the contacts of the associated connector relays. In this instance it may be assumed that a circuit is established for the group relay 608 to show the subgroup of trunks requiring service. A circuit is now established for relay 313 belonging to this subgroup. There are a plurality of trunks in each subgroup served by the same start relay 311. These are represented in the control circuit by a plurality of relays, such as relay E00. It will be remembered that a start ground was placed on conductor 320 of the incoming trunk when the start circuit was established. This ground operated relay 311 but at the same time extends ground through a plurality of contacts on relay 312 and a plurality of contacts on relay 313. There are as many contacts on relay 312 and 313 as there are trunks in a subgroup. This plurality of contacts is represented by one contact on relay 312 and contact 5 on relay 363. There are as many trunk relays 600 as there are trunks in the subgroup, all of which are initially operated from the start ground extending through one of the contacts on relay 312 and relay 313. The operation of these relays associates ground through a chain circuit, such as shown on contact 2 of relay 600, contact 6 of relay 313, winding of relay 312 to battery. 'I'he energization of relay 312 releases the start relay 311 and opens the leads from all trunks except the calling incoming trunk. The start ground therefore extends through only one contact of relay 313 through the winding of a relay 600 representing the calling incoming trunk. This relay remains operated and the relays associated with the other trunks are released. Relay 600 locks over the operating circuit traced to the start ground. The operation of the relay establishes the level of a primary switch to which the incoming trunk is connected and immediately establishes a circuit for the select magnet 304 for this level of the primary switch. This circuit may be traced from battery through contact 1 of relay 600, Contact 2 of relay 31'1, winding of select magnet 304 to ground. The operation of select magnet 304 connects ground through its contact and through contact 3 of relay 3H, winding of control circuit relay 601 to battery energizing the latter relay. The operation of relay 600 now establishes a circuit to determine the class of service required by the incoming trunk. This class of service is determined by the operation of one of a plurality of relays, such asrelay 603, in the control circuit. Since, in y.this case, only one class is required, a circuit is shown established for relay 003 through the apparatus of the incoming trunk circuit. This circuit may be traced from ground through contact 4 of relay 500, contact 1 of relay 3H, contact 3 of relay 313, conductor 330, contact 9 of relay 252 of the incoming trunk circuit which is operated thence over lead 331, contact 4 of relay 313, contact 8 of relay 311, winding of class relay 603 .necessary for the release of the control circuit.

'to battery. The operation of this relay connects The operation of relay 4II removes ground from battery through its contact, contact II of relay 3I1, contact 1 of relay 3I3, winding of relay 3I4 to ground. As previously stated there are as many contacts on relay 3I4 as there are channels associated with the control circuit. An idle control circuit establishes circuits for one or more relays, such as 505, in the control circuit. This circuit may be traced from battery through the winding of relay 605, contact I3 of relay 3I1, contact of relay 3i 4, lead 34I, contact 2 ofrelay 4II to ground on'contact I of relay 40I. The establishment of this circuit indicates an idle channel in a switchboard position attended by an operator since, as previously described, relayr 40I is only operated when the operator is attending the switchboard position circuits. The operation of relay 335 establishes a circuit for operating the double test relay 3I5 as shown from battery through contact I of relay 605, contact I4 of relay 3H, winding of relay 3I5, to ground. Since relay 305 is individual to the idle channel selected, the testing circuit of the control circuit is applied to the apparatus of this channel. This testing circuit comprises delicate apparatus which f vmay operate if two control circuits are associated with the same channel. This testing circuit has been limited to relay 6I0 which is now associated with the idle channel over a circuit from 24-volt battery through its winding, contact if 4 of relay 605, contact I5 of relay 3I1, contact of relay 3 I 5, lead 340 to Llil-volt battery connected with contact I of channel relay 4I I. The operation of relay 605 also establishes a circuit for the select magnet associated with the level of the secondary switch connected to this idle channel. This circuit may be traced from battery through contact 3 of relay 605, contact 4 of relay 3I1 through ground through the select magnet 3I8.

The operation of the select magnet connects;

ground through its contact, contact 5 of relay SI1, relay 602 to battery. The operation of relay 6I0 indicates that no interference has been encountered in the selection of the idle channel and establishes a circuit for relay 600. All of the` elements to be used have now been tested and the mechanism associated therewith energized. The operation of the select magnets of the priymary and secondary switches energizes relays The test of the channel associated!V 60I and 602. with the secondary switch Was made by the energized relay 606. A circuit may therefore be established at this time for energizing the hold magnets of this switch combination for connecting the incoming trunk with the selected charl-` relay SI1, contact 2 of relay 605, contacts of:

relays 303, 60| and 602 to ground. A circuit is also established for relay 4I0 from battery through its winding, contact 2 of relay 403, contact 1 of switch 302, contact 1 of switch 300,

lead 32 I, contact 2 of relay I I2, to ground throughY contact I of relay II3. The operation of relay 4I I disassociates 48-Volt battery from the testing circuit lead 343 and connects ground therewith. This causes a reversal in the testing circuit of the control circuit releasing relay 6I0 which is the test lead 34| and this lead now remains open. This causes the release of relayA 305 in the control circuit which enters into the release of the control circuit. This control circuit Will now be released as soon as the trunk start circuit is opened.

Position channel The operation of relay 4H establishes obvious circuits for lighting the busy lamp 401 and the guard lamp 446. Relay 4I0 establishes an obvious circuit for lighting guard lamp 449. The operation of both relays 4H] and 4H establishes a circuit for energizing the channel preference relay 402. There are as many relays, such as 402, as there are channels in a cordless position. These relays, such as 402, 420 and 42|, are in a chain circuit to prevent seizure of more than one channel at a time or seizure of one channel in a position when another channel is connected to the operators headset. The operating circuit for relay 402 may be traced from battery through its winding, contact I of talking relay 4I0, contact 3 of relay 4I I, contact 2 of relay 432, contact I of relay 10I to ground. Other operating circuits for relay 402 are also established through contact 2 of the monitoring relay 452 when operated or through contact 4 of the backward relay 4I3 when the latter relay is operated. Relay 402 in operating establishes a locking circuit for itself from battery through its winding, contact I of relay 4 I 0, contact 3 of relay 4I I to ground through its contact 2. This relay also opens the operating circuit for relay 10| extending through its contact I and establishes a circuit for relay 4I3. The circuit for relay 4I3 may be traced from battery through its winding, contact I of relay 432, contact of the operators jack 504, contact of emergency key 535, contact I of backward release relay 500 to ground. The release of relay 10I opens a circuit for relay lill to cause its release so that all channels of the position are made busy during the period required by the operator in serving a call entering her position. This includes supervising operations, such as talking to either a calling or a called party or monitoring as explained later. The operation of relay 4 I3 establishes a circuit for operating relay 402 from ground through contact 4 of relay 4I2,

"contact 6 of relay 4I3, winding of relay 403 to battery. This alters the guard lamp 403 from a steady to a flashing condition by the connection of ground from interrupter 408 through the lamp filament. This flashing signal indicates to the position operator that an incoming trunk has been connected to an idle channel of the position as a preparatory signal in advance of a tone signal given to the operator a fraction of second later. Relay 4I3 establishes a locking circuit for relay 4I I and a holding ground circuit through its contact 3 and contact 4 of relay 4I I for the of relay 003, contact 1 of relay 500, contact I0 of relay 403, winding of relay 404 to battery. The latter relay locks to its operating ground. The operation of relay 403 now energizes relay I I2 in the incoming trunk circuit for opening the link-start circuit extending to relay E of the link-control circuit. The circuit for relay I|2 may be traced from ground on contact I of relay 504, Contact I of relay 503, contact .0 of relay 403, contact i2 of

switches

302 and 300, lead 332, contact 2 of relay H1, contact 3 and the winding of relay H2 to battery. Relay I|2 establishes a locking circuit for itself to ground on contact 6 of relay 203 over a circuit including contact 4 of relay I I3, Contact 2 of relay |04, contact 3 of relay 202 and contact 'I of relay I I1. The operation of relay I I2 removes the start ground from lead 320 which extended through its contact I and causes the release of relay 50|! in the link-control circuit. I'he release of relay 600 causes the release of relay 608 which releases relay 3I3. The release of relay 3I3 opens the locking circuit for relay 3|| which releases and, in so doing, releases relay 3|1. The release of relays 3I3 and 3|1 opens the circuit of all relays in link-connector and linkcontrol circuits. The link connector and linkcontrol circuits may now serve other calls entering the telephone oice. As previously stated, a ground is supplied from the position circuit for maintaining the hold magnets 305 and 301 operated and, therefore, the switch connection bei,

tween the position channel and the trunk remains established.

Class of trunk signals The operation of the previously described relay 1I3 in one of the channels connects ground from its contact I through the winding of position relay 102 to battery. The operation of the latter relay connects ground through its contact 2, contact of relay 500, contact I of the class relays III1 and II I9 to battery through the winding of class relay 109. Relay 109 operates and connects leads 1I5 and 1| 6 through its contacts I and 2 to the windings of class relays II2I, II22,

I |23 and I |24 to battery through resistances I |25;

and H26, respectively, thus starting class determination. The ground from. contact 2 of relay 102 also extends through contact 5 of relay 500, contact 3 of relay 109, winding of relay 1I0 to battery. Relay 1|0 opens leads 1|8 and 1|9'l extending to the operators telephone circuit and establishes an operating circuit for relay 1|| which may be traced from battery through the Winding of relay 1| I, contact I of relay 1I0, contact 5 of relay 500, contact 2 of relay 102 to;

v nected to the cordless position for toll or terminating connections may be of the ringdown or straightforward type from distant toll o'ices or from tandem offices and they may vary in transmission characteristics. For example, a Via intertoll outgoing trunk must be selected by the marker for a call from a distant toll office which shall be routed outgoing to another toll oflice. On the other hand, if a call is for a connection which may extend from one toll oice to this toll oiice and is terminated in a local subscribers station, it is not necessary to use a toll trunk of the equivalent transmission characteristics as v some combinations that are made.

lthrough the Winding of relay 106.

used for the via connection. There are also `trunks which are of these characteristics in so far as transmission qualities are-concerned but which have different signaling devices, such as the difference in signals between the straightforward intertoll trunk and the ringdown intertoll trunk. The class signal in each case indicates vthe character of the trunk by associating a grounded circuit which may or may not have resistance in series therewith and open circuits in Various combinations with the class relays. These are connected from the trunk circuit, Fig. 2, through the contacts of relay 20| or a similar relay in a diiierent intertoll trunk circuit over

leads

333 and 334 through the cross-bar switches of Fig. 3, contacts 1 and 8 of relay 4|3 to the class relays II2I, ||22, II23 and II24. These relays are marginal and, consequently, operate according to the resistance in series with the energizing circuit. The following are examples of Il a grounded resistance is connected to lead 333 and lead 334 remains open, relay II2I operates which energizes relay III1. The latter relay is operated from battery through its winding, contact of relay |I2I to ground on contact II of relay 1|I. Relay II l1 when operated locks to this operating ground. When lead 333 is connected directly to ground with no resistance in series therewith, relays II2I and ||22 are operated which causes the operation of relays I I I1 and III8, both locking to ground `on contact II of relay 1| I. The same combination is used where lead 334 is either connected directly to ground or grounded resistance which operates relay II23 in one case and both relays II23 and |I24 in the other case. This causes the operation of either relay |I|9 or both relays I I I9 and I |20 which lock in the same ma-nner as described for relays III1 and III8.

Varied combinations are used throughout to indicate the characteristics of the different trunks. These indications are later transmitted to the sender and marker and are used for establishing circuits as will later be described.

Splitting relay It will be noted that when any class determination is made the operating path for class relay 109 is opened by the operation of either relay II|1 or |II9, thus causing the release of relay 109. This relay is slow to release to allow time for class determination. The release of relay 109 operates relay 106 and releases relay 1|0. The circuit for relay 106 may be traced from ground through contact 5 of relay 1I I, contact 5 of relay 109, contact 6 of relay 500 to battery During the foregoing operations a check is made for the sleeve holding ground provided by the incoming trunk circuit when relay 202 was operated as previously described. If this ground has been properly associated with the sleeve lead, a circuit is established for relay 108 which may be traced from battery through the windings of relays 108 and 101 in series, contact 6 of relay 504, contact 6 of relay 5I6, contact 5 of relay 80|, contact 4 of relay 803, contact 1 of relay 4I3, contact 9 of the link switches, Fig. 3, thence over lead 329 through contact 9 of relay 20| and contact 4 of relay 202 to ground. Relay 108 is locked to ground on contact 8 of relay 1| I. This holding ground later serves to hold the switch hold magnets operated on a connection which has been established when the splitting relay 20| is operated for talking to the called party. Relay 101 is a lwith responsive to calls of different character.

polarized relay and does not operate unless the circuit traced is associated with a connection which has already been established. If this circuit is associated with anestablished connection,

battery through the switch hold magnets will operate relay '|01 to ground on contact 8 of relay 'III or to ground on contact 2 of relay '106. When this relay is energized a circuit is established for relay 800' through the contact of relay '101, contact 4 of relay III, contact 2 of relay '|I0, contact 5 of relay 500 to ground on contact The operation of relay 800 supplies ground to the position circuit for lighting lamp |I0 to show that the position is associated with an established connection. Relay |01 is also used in connection with the release of the position apparatus. The operation of relay '|06 over the circuit previously established associated ground with lead 1|'I to operate the splitting relay 20| of the incoming trunk over a circuit which may be traced from ground on contact 3 of relay 500 through contact I of relay 106, lead III, contact 0 of relay 403, contact 6 of

switches

302 and 300, contact 4 of relay ||2, winding of relay 20| to battery. Relay 20| in operating establishes a holding circuit for relay II3 from battery through its winding, contact 4 of relay 20|, thence to the operating ground for relay 20|. Relay I I3 remains operated after the release of relay 20| over a circuit traced from battery through the winding of relay I3, continuity contact of relay 20|, contact 5 of relay II3, contact 2 of relay |04, contact 3 of relay 202, contact 'I of relay II'I, contact 6 ofrelay 203 to ground. This splitting relay 20| is released when conversation between the operator and the calling operator has ceased and part of the position Aapparatus is released. At this time, however, the

splitting relay 20| is operated to disassociate the 'inward and forward ends of the trunk and associate the forward end with the cordless position circuit for signaling purposes and for conversation between the operators. such as 404, of the position channel is operated if no other'forward relay in the sequence circuit is operated. A circuit 'for this relay is established as described when the backward relays 403 and 4I3 of the channel operate. Relay 404 establishes a circuit for relay 5I5'over an obvious circuit and the latter relay establishes a circuit lfor-relay '|05 which ties the forward and backward portions of the position circuit together for service on the same call. The circuit for relay '|05 may be traced from ground through contact 3 of relay SI5, contact 3 of relay 803, winding of' relay '|05 to battery.

Position signals be traced to the position circuit through contacts I of the link switches 300 and 302, contact 2 of relay 403 and thence through the windings of marginal relaysV |0I4, |055 and IOI6 to ground. The number of these relays operated depends upon the value of `resistance associated there- The forward relay,

For example, when a call isa new call or connection to an outgoing toll trunk, relay II2 is operated which associated resistance IIO in circuit with relays IOI4, |0I5 and |016. The value of resistance I|0 is such that only relay |0|4 is operated. This establishes a circuit for relay |003 from battery through its winding, normal contact of relay |0I5, contact of relay IOI4 which is operated to ground. This indicates that the call to be answered by the cordless operator is a new call. In this case the apparatus of the position toll circuit will establish a circuit for relay IOI'I. In the case of a recall from the calling distant operator, the same circuit will be established with the exception of the circuit for relay IOI'I. In the case of a recall, relay 800 in the position control circuit is operated and there will be no circuit for relay |0I'I. Therefore, on a recall a circuit is established to light lamp |0I0 and a distinctive tone is transmitted to indicate this type of call. When a manual recall is made from a called oice, circuits are established for relays I I2, 201 and 204 of the incoming trunk circuit, Figs. 1 and 2. The operation of the above three relays connects resistances 222 and |I0 in multiple and these multiple resistances are connected in series circuit with relays |0I4, I0|5 and IOI0. The value of resistance 222 in multiple with resistance H0 is such as to cause the operation of relays IOI4 and I0| 5. The operation of both relays I0| 4 and IOI5 establishes an obvious circuit for relay |002 which lights lamp IOI and associates a distinctive tone with the operators headset. A different signal is given when the distant called party does not answer. In this case, incoming trunk relays I|2 and 201 are operated which connects resistances 22| and IIO in series with relays IOI4, I0I5 and IOI6. The Value 4of resistance 22| in multiple with resistance IIII is such as to cause the operation of all of the aboverelays. The operation of these three relays establishes an obvious circuit for both relays |002 and |003 which'lights lamp IOI2 through their contacts and establishes a circuit for a distinctive tone. v

The tone circuit, known as the order tone, for indicating to the operator that a particular connection has been established which is either a,

new call, a recall or that'the connection desired has not been established. This tone circuit is established by the operation of relays shown in the left portion of Fig. l0 over the control relays IOI4, |0I5, I0|6, |002 and |003. The operation of eitherrelays |002 or |003 indicates to the position operator that the incoming call is from a ringdown intertoll trunk and also establishes a characteristic circuit to the marker. With these relays released circuits are established for indicating that the call is from a straightforward intertoll trunk. In the case where both relays are released, three pulses of order tone are transmitted toboth the distant operator and the cordless operator. When only one of the aboverelays is operated, the tone will be transmitted only to the cordless operator. One pulse of tone is transmitted when relay |002 is operated and two pulses of tone are transmitted when relay! 003 is operated.

Position tone circuit The order tone circuit is established from the position control circuit which associated ground with lead |029 through contact 4 of relay |004, lead |030, contact 4 of relay |020, contact'lI of relay ||8, winding of relay |02| to battery. Relay |02| is the i'lrst of a series of operations for energizing and deenergizing the tone circuit. This tone circuit may be traced from tone source |022 through Various contacts of relays |0|3,

|0|8, |,0|9, |020 and |02|, thence through the right winding of tone transformer |005 to ground. The tone is transmitted by induction through tone transformer |005, contacts I and of relay |004 to the talkingconductors which in one case extend through contacts and 4 of relay ||0| and the windings of transformer ||02 by induction to the cordless operators headset. As previously stated, on certain calls the tone is transmitted only to this cordless operator but when a call is transmitted ov`er a straightforward intertoll trunk, relays |002 and |003 are both released and the tone is transmitted through contacts and 5 of relay |003, contacts I and 6 of relay |002, thence to the contacts of relays |00| and |000,

contacts

3 and 4 of relay 403 to the trunk conductors.

The operation of relay |004 separates leads |029 and |030 at its contact 4, thus releasing all of the relays which were held to this ground including |0|3, |0|8 and |02I.

The foregoing describes the operation of the tone circuit for transmitting three tones which is the maximum used in this circuit arrangement. As previously explained, three tones are used when the toll call is incoming over a straightforward trunk and may indicate a new call over this trunk or a recall by the originating distant operator. A call from an originating operator over an incoming ringdown trunk actuates relay |003 either when this call is a new call or when it is a recall from the originating operator. A recall from the called party operates relay |002 and the called party does not answer both relays |002 and |003 but relay |002 is the only one effecting the control of the tone circuit. Under the condition of a new call or a recall from the originating operator, using an incoming ringdown intertoll trunk, the operation of relay |003 causes one pulse to be transmitted to the cord- The talking circuit to the incoming trunk is opened to contacts and 5 of relay |003 and thus this one pulse does not reach the incoming trunk. The operation of relay |003 establishes a circuit for relay |004 after one pulse has been transmitted. This circuit may be traced from battery through the winding of relay |004, contact 2 of relay |002 which is normal, contact 2 of relay |004, operated, Contact of relay |0I9 which is operated at this time, and thence to ground over leads |030 and |029 through contact 4 of relay |004. Relay |004 in operating operates leads |030 and |029 and locks -through its Contact 4 to lead |029. As previously stated, the operation of relay |004 releases the tone actuating relays and ends the transmission of tone after one pulse. The operation of relay |002 on a recall from a called toll oice or information operators desk causes the transmission of two pulses to the cordless operator. These pulses do not reach the incoming and outgoing trunks. The operation of the toll circuit relays proceed as previously described until relay |020 operates a second time. A circuit is thus established for relay |004 from battery through its windings, inside contact 2 of relay |002, contact 2 of relay |0|8, contact 2 of relay |020, contact 2 of relay |02I to ground over lead |029. Relay |004. opens the tone circuit as previously described and locks through its contact 4 to lead |029.

The foregoing indicates the action in the cordless toll operators position circuit both for a new call entering this position as previously described, and for a recall from a distant operator. It is assumed for this description that the distant toll operator in toll oice |00 requests a connection to an operator in a distant toll oflice over a via intertoll trunk and, consequently, the apparatus of the sender 900 and the marker must be actuatedin a manner to actuate the

cross-bar switches

282 and 285 for connecting the incoming intertoll trunk, Figs. 1 and 2, with an outgoing trunk 230 extending to ofce 28|, disclosed diagrammatically in the right portion of Fig. 2. Reference is made to the Patent 2,236,246 to King, McKim, Myers, March 25, 1941, for a com- Vthrough its contact I.

plete description of' thev cordless toll position equipment, positionr control circuit, position sender 900 and marker 90| forfoperating the apparatus of. this oliice` to complete thev connection between the. incoming intertoll trunk: and the information operators trunk. In order to simplify this description,y only the, partsk which are. involved in carrying out the operation of this. invention are disclosed anddescribed.

Sender During the foregoing operations which provide a signal tothe operator indicating'a call has entered the position andthe character of the incoming call, a circuitis established for the sender start relay 104 as soon. as certain relays are in the following position:y Relay 102 operated, relay 500 released, relay 1I0" released, relay 1II operatedy relay 101 released, relay 105' operated, and relay 10.3 released; The positioning of the foregoing relays was-established as'previously described. The circuit for the4 sender start vrelay 104 may thereforebe tracedfrom ground through Contact 2l of relay 102', contact 5 ofv relay 500, contact I of` relay 1I0, contact 4 of. relay V1 II, contact of relay'10'1, contact 5: of relay 105, contact 2 of relay 103, winding of relay 104 tov battery. Relay-'1041 locks through contact I of" relay SIG, contact 5 of position release relay 804 to ground through Contact 2 of relay 5I5'which was operated by relay 404. The operation of the sender start relay 104r establishes an operating circuit for senderl control relay 925. in the sender 900 from ground through contact 3y ofr relay 104, winding ofi relay 925-to battery.` Relay 9.25 operaltes relay'103 from battery through its winding, Contact 2 of relay SIS, contact ofv relay 925 to ground. Relay 103 locks to thissame ground The operationv of the latterrelay opens the operation path for' the sender start relay 104 which now remains operated under the control of its locking circuit which extends through the position release relay 804; Relayy 103fis slow in operation to guard against too rapid seizure of the sender.

The elements of the position sender may be roughly divided with respect to theirvfunctions into principle parts, the key-set, the register ciry The position sender is now in readiness to receive registrations from the position circuit. The

cordless toll operator upon observing a lamp signal and receiving a tone signal indicating the type call to beanswered challenges the distant operator which in this case is a toll operator at toll cflice IIl0 and receives the codeor code and numerical designation of a wanted party.` In certain cases where therx connection to another distantv toll oice is; desired only the code number isgiven to the cordless tolll operator. When a call incoming from another toll olice terminatcs in the area of the toll olice receivingthe call, the code designation and numerical designation may be given by the calling toll operator so that a telephone connection can be completed in thisarea by the cordless toll operator. A large Variety of combinations ofV interconnections between incoming trunks of various, character and outgoing trunks of various character are pro-.T

vided. For this` reason numerous combinations of call registrations are required both for indicating the character of the calling incoming trunkand the character of the outgoing trunk required for completing the connection. Only suicient apparatus combinations are shown to carry out the operating circuits of the invention.

The cordless toll operator manipulates the keys of the position key-set for energizing registers in the sender. These registrations in the sender are transferred to the marker after the energization of a marker connector by the sender which associates the sender with an idle marker. There are only a small plurality of markers by comparison with the plurality of senders inthis character of toll oflice and consequently a markery connector is used for finding an idle marker: and associating the sender which has been energized'with this idle marker. Registrations are transferred to the marker covering the routing of this connection and the character of" the calling incoming trunk circuit. This includes the character of the outgoing intertoll trunk to be used for the connection. The above registrations in the marker are used for completing the telephone connectionV and for controlling apparatus ofthe cordless toll position as soon as this connection has been made. This automatically adjusts the incoming trunk circuit to either arrange circuits for placingvthe telephone connection under the constant supervision of: the cordless toll operator by locking the link switches ofthe channel or for indicating that this supervision isnot-required.

Call registrations Were transferred to the marker from the yclass registers in the lower portion of position circuit, Fig. 11, for indicating the class of the incoming trunk by operating relays 9I'I`, QIZ or 9I3. The operation ofv relay SI2 signals the marl'cerv that. the calling incoming runk is` a via incoming trunk of the highest transmission cllaracteristic. The operation of relay: SI Iy signals the marker that the calling incoming trunk is a terminal trunk. When relay BI I` is energized the telephone connection may beA extendedv either to a distant toll oice and therek terminated or it may be extended to a local oicezin the areav of this toll oiiice. An incoming call over a via intertoll trunk may terminate in a local' oice `in the area of' this toll office. In this case re1ayJ9'I2 will be energized to indicate` an incomingcall over a via intertoll trunk and also relay 9I'3 will be energized by the coder registers to indicate the terminating area of; the call. The energization of route relay 005, along with other apparatus not shown, is for a via connection to an intertoll trunk extending to another distant toll ofce. When the incoming intertoll trunk is a via intertoll trunk and. the outgoing trunk is a via intertoll trunk the connection requires supervision and therefore the route relay energizes a class relay 908 which establishes a combined circuit for automatically locking a link between a position channel and the calling incoming trunk. This circuit, however, is not completed until the via outgoingk trunk has been selected by the marker andthe switching paths completed between this idle outgoing trunk and the calling incoming trunk.

The energization of relay SI I by the class relays and the energization of a route relay, such as route relay 901, establishes a circuit for relay t: in; the sender control circuit instead of relay G06.. In this case the route relay ener-