US2400061A

US2400061A - Telephone system

Info

Publication number: US2400061A
Application number: US527636A
Authority: US
Inventors: Henry H Abbott; Henry M Bascom
Original assignee: Bell Telephone Laboratories Inc
Current assignee: AT&T Corp
Priority date: 1944-03-22
Filing date: 1944-03-22
Publication date: 1946-05-14
Anticipated expiration: 1963-05-14

Description

May 14, 194e.

H. H. ABBOTT ET AL TELEPHONE SYSTEM Filed wia/rch 22, 1944 4 Sheets-Sham*l 1 H H ABBOTT H, M AscoM ATTORNEY NI/ENTORS May 14, 1946. H. H. ABBOTT Erm. 2,400,051

TELEPHONE SYSTEM Filed March 22, 1944 4 Sheets-Sheet 2 SUB STA.

H H ABBOTT WENTORS' H. M AscoM I er A TTORNE Y May14,1946. H. H.ABB 5TT UAL l 2,400,061

i TELEPHONE SYSTEM Filed March 22, 1944 4-SheetS-Shee13-3 y 'H H ABBOTT /NVE'NTORS By WMW A TTORNEV May "14, 1946'. H. H. ABB'TT ETA. 2,400,061 TELEPHONE sYsTVEM Filed Maron 22,/ 1944 4 sheets-sheet 4 REGIS TE R M1-TO HMBAscoM TME-5MM ATTORNEK Patented May 14, 1946 UNITED STATES PATENT OFFICE TELEPHONE SYSTEM Application March 22, 1944, Serial No. 527,631l

Claims.

This invention relates to telephone systems and particularly to systems in which automatically operated switches are employed to establish connections between subscribers lines.

An object is to simplify the automatic equipment and to economize in the use of such equipment.

Heretofore so-called cross bar switching systems have been used in various forms to establish automatic connections between subscribers lines. For example in small capacity systems of the order of from 1 to 200 subscribers lines, a single cross bar switch was used in which each subscribers line terminated in a separate row of contacts such as in a vertical row, while links for connecting the subscribers terminated in the horizontal rows. 'Ihe arrangement was such that a calling subscribers line was connected at the crosspoint of his vertical row of contacts with an outgoing branch of an idle link in a horizontal row and the called subscribers line was connected at the crosspoint of his vertical row of contacts with an incoming branch of this seized link in another horizontal row Vso that the connection extended from the calling subscribers line through this two-ended link to the called subscribers line. These connections were established by the usual means of select magnets and hold magnets operating on intersecting bars in a manner well known in the art.

It is a feature of the applicants invention to employ instead of such two-ended links, means whereby a connection between a. calling subscribers line and a called subscribers line is extended over a single-ended link in the same horizontal row of contacts. That the calling line is connected at the crosspoint of his vertical row of contacts and the contacts of an idle horizontal row of link contacts and the called subscribers line is connected atv the crosspoint of his vertical row and contacts ofthe same horizontal row of said seized link.`

Another feature oi' the applicants invention is to provide `a ringing equipment for ringing the called line over one conductor of the line from the single-ended link and the called line through the called subscribers ringer to ground and through a ringingtrip relayconnected in series with a ringing source and so arranged that this relay is energized while ringing is taking place and released when the called subscriber answers as a result of the opening of the ringing path to the called spbscribers ringer to ground. The release of said relay disconnects the ringing source and establishes the talking connection. This arrangement also provides that the ringing is tripped only during a ringing interval and thereby prevents any loud clicks in the calling subscribers receiver while tripping takes place which would occur if the tripping would take place during a silent interval.

The applicants invention has lbeen illustrated in the accompanying drawings in which:

Fig. 1 shows in schematic form a typical layout of the applicants invention in connection with a cross bar switch; and

Figs. 2, 3, 4 and 5V arranged in theorder as shown in Fig. 6 disclose in detail the circuit arrangement for carrying out thev applicants inventionin a small capacity system.

Referring now to the drawings and particularly to Fig. 1, the arrangement shown may consist of a single cross bar switch 5 divided into two sections' and '7 having a capacity of ten subscribers each. That is, in section 6 there are ten vertical rows of contacts for ten subscribers lines as indicated at 8 and in section 'I there are another ten subscribers lines terminating in ten vertical rows of contacts indicated at 9. The horizontal rows of contacts may -be divided in six single-ended links shown at I0 and four outgoing trunks shown at Il. These links may be provided with a separate group of control relays such as I2 for link No. land common control relays indicated by the box I3, while a common register as indicated at I4 and an idle link allotter' arrangement at I6 with a common ring arrangement at I'I. If a connection is desired, for example, from a subscriber No. 1 to a subseriber No. l1, the subscriber No. 1, removing his receiver from the switchhook causes a connection to be established over,for example, the link 20, allotted by the allotter I6, through crosspoint ZI to theregister I4 over the individual relays I2 and the common relays I3. He then after receiving dial tone dials the number of the desired subscribers line which requires a first digit determining whether the calling subscribers line is in group 8 or in group 9 and a second digit determining the individual subscribers line. When the dialing has been completed the register I'4 operates these mechanisms to establish a 'connection at the crosspoint 22 between the Vcalled subscribers line and the link 20 and the ringing equipment I1 is then operated to ring the called subscriber over the chosen link. When the called subscriber answers, the ringing equipment I1, the common relays I3, the register I4 andthe allotter I 6 are released for common use and the talking circuit is established from the calling subscriber No. l through the cro-sspoint 21 over link 20 to the called subscriber No. 11 through crosspoin't 22. A trunk connection is established by, for example, a subscriber No. 1 by a single connection at a crosspoint such as, for example, 25 between the subscribers line No. 1 and the iirst trunk 26 or if this trunk is busy at a different crosspont to the next succeeding idle trunk. The trunk may extend to a distant oice, central oce or a private branch exchange.

Referring now to Figs. 3 to 5, a call will be traced from a calling subscribers line to a called subscribers line over these circuits. followedl by a description of a call to a trunk from a calling subscribers line.

In Fig. 2 the cross bar switch 200 has been shown with the connections for one subscribersv line with his station equipment as shown at 201. In this switch have also been shown the connections terminating in the box 202 which would contain the same station equipment for another subscribers line. The individual control equipment for one link 203 has been shown in Fig. 2 and the common control circuit arrangement as been shown partially in Figs. 3 and 4: the allotter has been indicated by a box 400 and. similarly the standard register by a box 001 While the ringing equipment has been shown in Fig. 5.

It should be noted that a subscribers station equipment consists of a series of hand-operated keys indicated at 205, the

key parts

1, 2, 3 and 4 are for the purpose of selecting outgoing trunks one of which has been shown at 206', while the key marked L is for the purpose of starting the operations to establish connection between a calling subscriber and the register and the common equipment over a link such as a linkl 203 which is the rst link While 200 represents the sixth link. Key H is provided for holding purposes but is of no importance as far as the present invention is concerned.

If it is assumed that the subscriber at station 201 desires to establish a connection to another subscriber such as 202, for example, this subscriber will remove his receiver from the switchhook and press his key L. This closes a circuit for the operation of line relay 210 from battery, contacts of the hold magnet 211, which is used for establishing connections for this Calling subscribers lines in the switch 200, through the Winding oi relay 210, a winding of the repeating coil 212, transmitter 213, contacts of the dial 210, switchhcok contacts 2 I 5. contacts of relay 210 to ground at contacts of cut-oir relay 216. This closes a circuit for the individual relay 301 for the calling subscribers line in series with a start relay 403 from battery over a winding of this relay 403. through a circuit in the link allotter 400 over a start lead, contacts of relay 210, contacts of the operated key L and the closed

contacts nf keys

4, 3, 2 and 1, switchhook contacts 215, contacts of relay 210, winding of relay 301 to ground at relay 302, causing the operation of these relays 4.03 and 301. The relay 301 represents the rst subscribers lines in the first group of ten, that is, subscriber No. 1 in group 6, while the relay such as S represents the first subscribers lines in the second group of ten and it is understood that eighteen other similar relays not shown represent individually 2 to 10 and 12 to 20 subscribers lines. These relays are interconnected in various ways as will be described hereinafter. On the other hand, the start relay 403 is located in the control circuit for link 203 and this relay and the corresponding start relay in the other links may be connected in succession through the allotter 000 to the common start lead and through the contacts of all line relays such as 210 and 21'1 for

lines

1 and 20, respectively. The direct result of operation of relay 301 is that relay 306 is operated from battery through the Winding of this relay, contacts of relays 301, 308, contacts of relay 301 to ground. Relay 306 closes a circuit for the operation of relay 308 from battery through` the winding of this relay, contacts of relays 301 and 30B to ground. Relay 308 opens the circuit for relay 306 which now releases slowly and relay 308 locks over a circuit through its winding, contacts of relays 30",', 300 and 301 to ground. When relay 305 releases a circuit is now completed for the select magnet for the link chosen, in this case link 203, and consequently the select magnet 220 is operated from battery winding of this magnet, contacts of

relays

409, 403, 300, 308, 301 to ground. The operation of this select magnet prepares connections for extension over links 203 and closes an obvious circuit for the operation of relay 310 which in operating closes a circuit for the cut-01T relay 216 of the calling subscribers circuit from battery through the winding of this relay, contacts of relays 301 and 310 to ground. Cut-off relay 216 closes an obvious circuit for the operation of the hold magnet 211 which now connects the calling subscribers line at the crosspoint 222 to the link 203. Hold magnet 21 1 opens the circuit for the relay 210 which now releases. Relay 210 in releasing releases relay 301, while the start relay 403 remains operated from battery over its two windings and its own contacts through the contacts of relay 406 over the ground supplied at the crosspoints 222 over the lead 223. Relay 301 in releasing releases relay 300 and also the select magnet 220 while cut-off relay 210 is maintained operated over the connection through the crosspoint 222 to ground over the connection through keys L, l, 2, 3 and 4. svvitchhook contacts 215 and contacts of cut-olf relay 210 to ground. Dial tone is now transmitted to the calling subscribers line from the dial tone circuits in Fig. 5 from ground through one of the windings of the repeating coil 502, the circuits for starting the dial tone being completed on the operation of relay 403. That is, this relay 403 applies ground at its contacts to operate relay 503 alternately through its self-interrupting contacts. The dial tone is induced thereby through the windings of repeating coil 502 to the tip side of the subscribers line over lead 504, contacts of

relays

403 and 401 and a winding of relay 400.

The calling subscriber may now dial the desired subscribers number which consists of two digits, one to determine the group of ten subscribers in which the called subscribers line is located and the second to determine the number of the subscribers line in this group. As the connection is established from the calling subscriber by the operation of the dial 214 through the switch 200, the relay 1508 is operated through both windings over the tip and ring conductors. When this relay is first energized, a circuit is completed for the relay 400 from battery, the make-beforebreak contacts of this relay, contacts of relays 408 to ground over crosspoint 222 in switch 200. Relay 409 in operating closes a locking circuit for itself through its upper outer armature and front contact to this ground'in switch 200. This relay also opens at its lower armature and back contact a connection to the link allotter i to release it to allot another link for a succeeding call.

That is, the allotter now extends the start lead to another start relay in another link corresponding to start relay 403 in link 203. On the first release of relay 408, relay 4|I operates from battery through the winding of this relay, contacts of

relays

409 and 408 to ground at switch 200. Relay 4I3 is also operated from battery through the winding of this relay, contacts of relays 4I2, 4I4, 409 and 408 to ground. Relay 4I3, in operating, closes a circuit for the operation of relay 4I6 from battery through a winding of this relay, make-before-break contacts thereof, contacts of relays 406, 4I3, 4| I, 4I'I and 409 to ground. Then when relay 408 operates at the end of the first impulse, relay 4I4 operates from battery through the winding of relay 4I3, contacts of relay 4I2, 4I 3, upper winding of relay 4I4, contacts of relays 4II, 4|1 and 409 to ground and as relay 408 releases at the beginning of the second impulse, relay 4 I 2 is operated from battery, winding of this relay, the lower winding of relay 4I4, contacts of this relay, contacts of

relays

409 and 408 to ground, so that now relay 4I4 is held in series with relay 4I2, while relay 4I3releases. Relay 4I3 in releasing operates relay 406 from battery, a winding of this relay and its make-before-break contacts, contacts of relays 4I6, 4I3, 4I I, 4I'I and 409 to ground. Relay 4I6 opens the holding circuit for relay 403., Then when the relay 408 operates at the end of the second impulse, relays 4I2 and 4I4 are released. lIf only two impulses are received, it indicates that the called subscribers line is located in the iirst group of ten subscribers, that is, the same group in which the calling subscribers line is located. On the other hand, if a third impulse is received, the release of the relay 408 in response to this impulse would operate relay 4I3 which now would operate relay 420 over a circuit from battery, a winding of this relay and its make-before-break contact, contacts of relays 42|, 4I6, 406, 4|3, 4II, 4I'I and 409 to ground. Relay 420 would in this case transfer certain leads through the register to indicate that the -called subscribers line is located in the second group of ten subscribers lines. No further impulses can have any effect on the circuit as far as the selection of a group of subscribers lines is concerned as a fourth impulse would prevent this by the operation of the relay 42| on the release of relay 4I3.

If it is assumed that only two impulses have been sent, relay 4| I which is slow in releasing will release on the operation of relay 408 at the end of the second impulse and this relay in turn releases relay 4 IB, which connects the odd and even leads for the register for the control thereover by the second digit. Now when the second digit is dialed on the rst release of relay 408, relay 4II will again be operated which in turn will operate in this case relay 423 from battery through the winding of this relay and its make-beforebreak conta-cts, contacts of relays 406, 4I6, 4| I, 4I'I and 409 to ground. Relay 4I3 will also operate from battery through the winding of this relay, contacts of relays 4|2, 4I4, 409 and 40B to ground and an impulse will be sent to the register for recording this first digit from ground at contacts of relay 409, contacts of relays 4I'I, 4| I, 4I3, 40E,

4 I3 is released and ground will now be applied to a the even lead 421 from ground through contacts of relays 409, 4II, 4II, 4I8, 4I6, lead 421. This ground operates other relays in the register to record the second digit. If it is, however, assumed that only one impulse is received, relay 4| I will release on the operation of relay 408 at the end of this impulse. This causes the operation of relay 42| from battery through the lower winding of this relay and its make-before-break contacts, contacts of

relays

423, 4| I, 4II and 409 to ground. This connects the busy relay 428 to the lead, for example, 429 for the `called subscribers line which subscriber in this case would be the first subscriber in the second group such as the one whose equipment is shown at 202. A test will now therefore be made to determine whether this line is busyor not. This connection extends from battery through the upper winding of the busy test relay 428, its make-before-break contacts, contacts of relays 423, 42| and 420 through the register to the unit and test lead 429, contacts ofA the hold magnet 228 of the desired subscribers line connection at switch 200 through the winding of the cut-oil relay 229 to battery, that is, provided this line is idle. If the line is busy a ground will be found applied at the'contacts of the hold magnet 228 which will be operated in this case. Relay 428 will therefore operate from this ground and apply a busy tone to the calling subscribers line by first closing an obvious circuit for the relay 5I0 which closes an obvious circuit for the operation of relay 50,3. Relay 503 alternately operates and releases through its self-interrupting contact and thereby induces the busy tone through the transformer 502, while relay 5I0 also closes an obvious circuit for relay 5I5 which operates relay 5I4 which in turn operates relay 5I6. Relay 5I6 releases relay 5I5 which releases relay 5M and these operations are repeated at intervals depending on the slow-to-close characteristics of these relays to send busy tone signals from repeating coil 502 over lead 5I2 through contacts of relays 5I4, 5I0, 428, condenser 430 over the tip conductor to the calling subscribers line.

On the other hand, if the called line is idle as indicated by the released condition of the hold magnet 228, and relay 428 is not operated, relay 4I6 closes a connection for the operation of the relay 3 I 4 from battery, winding of this relay, contacts of relays 428, 4I6, 423, 302 to ground- Relay 3I4 is one of six relays for operating the select magnets in the switches 200 representing six links, this relay being the one associated with the chosen link. This relay 3| 4 operates relay 3I6 from battery, winding of this relay, contacts of relays 3I4, 423, 4II, 4I'I, 409 to ground and also relay 306 from battery, winding of this relay, contacts of

relays

308 and 3| 4 to ground. Relay 3I'I is also operated from battery, winding of this relay, through the chain circuit of relay 3|8 and the intermediate relays in the group to which relay 3 I4 belongs, contacts of relay 3I4 to ground at relay 302. Relay 3II locks over its own contacts to ground at the contacts of relay 3I4. Relay 302- is then operated from battery through the winding of this relay, contacts of relay 30T, contacts of relay 3I`I to the same ground at contacts of relay 3I4. This ground also furnishes a holding circuit for relay 3I4 through contacts of relay 3I'I. Relay 300 closes an obvious circuit for relay 308 over contacts of relay 301. Relay 302 closesa circuit for the operation of relay 301 from battery through the winding of this relay, contacts of relays 302, to ground at relay 3I4. A circuit is now completed for the operation of the select magnet 220 of the chosen link 203 from battery, Winding of this magnet, contact of relays 3|4, 3|6, 301 to the ground at contacts offrelay 3| 4, while relay 301 releases relays 306 and 300, the latter releasing relay 301. These relays 306, 308 and 301 are slow in releasing to permit select magnet 220 to remain energized long enough to perform its functions. The select magnet 220 closes an obvious circuit for the operation of relay 3|0 which latter relay holds this select magnet operated for an instant. Relay 3|0 applies a ground at its outer right-hand armature and front contact which causes relay 423 to release. This causes the operation of the cut-ofi relay 229 from battery through the winding of this relay, contacts of hold magnet 228 over the unit lead 420 which represents the first subscribers line in the second group and through the register 40|, contacts of relays 420, 42 to ground at contacts of relay 423. Relay 229 in operating closes an obvious circuit for the operation oi the hold magnet 228 which now closes a connection between the link 203 at the crosspoint 23| to the called subscribers line 202. Relay 220 is now locked over the sleeve connection at crosspoints 23| and crosspoint 222, keys L, 4, 3, 2 and l at the calling subscribers line, the switehhook contacts to ground at the cut-off relay 2|6. Relay 423 also causes the release of relays 3 i4, 3|6 and 3|1, while relay 3|4 releases the select magnet 220 and the relay 3|1 causes the release of relay 322.

As the calling and called subscribers lines are now connected to the same link 203 and as relay 423 is released, the ringing of the called subscriber will commence by the operation of the relay 401 over a circuit from battery through the upper winding of this relay, contacts of relays 4|1, 42|, 428, 40B and 423 to ground. The operation of relay 401 transfers the tip and ring conductors from the battery and ground through the windings of relay 408 through the windings of the relay 43| through the two windings 520 of the repeating coil 52| to battery and ground in the ringing circuit and also starts the ringing by closing a circuit for the operation of relay 522 from battery, winding of this relay, contacts of

relay

523, 524, 525 to ground at the contacts of relay 401. Relay 522 in operating applies alternating ringing current from the source 530 through contacts of this relay to the opposite winding 53| of the repeating coil 52| to ground. This applies a ringing voltage from ground through repeating coil 52| to both sides of the called subscribers line. As the called subscribers ringer is connected through a condenser to ground as shown, for example, at the calling subscribers line where the ringer is marked 250 and the condenser the circuit for ringing is extended irom ground and battery through the upper of the two windings 520, through the lower winding of relay 43|, contacts of relay 401, lower winding of relay 408 over the ring conductor through the ringer and condenser to ground at the called subscribers station, that is, the ringer and condenser corresponding to the ringer 250 and condenser 25| of the calling subscribers station. It should be observed that the tip and ring conductors are closed at the calling subscribers line for this connection through the upper winding of relay 408 and the upper winding of relay 43| through the lower right-hand winding of the repeating coil 52| to ground, but that there is no connection for the tip conductor at the called subscribers station. Consequently, due to the low resistance path through the ringer to ground at the called subscribers station through the lower winding of relay 43| and due to the fact that the windings of this relay are wound in opposite directions this relay will operate at this time. This causes the operation of relay 4|1 from battery through the winding of this relay, contacts of relay 43|, make-before-break contacts of relay 4|1, contacts of relays 42|, 428 and 406 to ground at relay 423. Relay 4|1 in operating closes a locking circuit for itself over the circuit to ground at relay 423 independent of the connection of the contacts of relay 43 Thus relay 401 is held operated while the ringing current is transmitted to the called line due to the operation of relay 43|.

It should now be observed that when relay 401 was operated, it closed a circuit for the operation of relay 5|5 which closes a circuit for relay 5|4, which relay in turn operated relay 5|5. Relay 5| 6 releases relay 5| 5 and this relay releases relay 5|4. This cycle of operations is repeated to close ground connections from relay 401 through contacts of relay 5|4 alternately for the

relays

525, 525, 524 and 523 for their ultimate operation and release. When this ground is iirst applied, it causes the operation of the relay 520 from battery through a resistance, winding of relay 526, its make-before-break contacts, contacts of relay 5|4 to ground at relay 401 and when relay 5|4 releases, relay 525 operates with relay 526 locked to this ground at relay 401. When relay 5|4 again operates, relay 526 releases, which causes relay 523 to operate from battery through a resistance, winding of this relay, contacts of relays 523, 52B and 5.25 to ground at relay 401. When relay 5|4 releases relay 525 releases causing the operation of relay 524 from battery through a resistance, contact of relay 523, to ground at relay 401. When relay 5|4 operates, a third time, relay 525` operates, when relay 5|4 releases relay 525 operates, when relay 5|4 is again operated, relays 52S and 523 release and when relay 5i4 releases, relays 525 and 524 release. These operations are repeated so as to alternately release and operate relay 522 at intervals as determined by the time release characteristics of relays 5|4, 555 and 5|5. That is, relay 522 releases on the first operation of relay 525 and operates on the first release relay 524, These operations are in the nature of one second for the application of ringing and three seconds for a silent period. Therefore when relay 522 releases for the first time, that is, on the operation of relay 525, relay 401 is held operated over a circuit from battery through contacts of relay 522, contacts of relay 401 and the lower winding thereof to ground at contacts of relay 4|1 while relay 43| releases due to the cutting off of the ringing current, then when relay 522 again operates on the rst release of relay 524, relay 43| operates and holds relay 401 operated. These operations continue as long as ringing is continued. Then when the called subscriber answers, the ringing is released only during a ringing period, that is, when relay 522 is operated. When the called subscriber answers under these circumstances, by removing the ringer through the condenser to ground at his station, relay 43| releases due to the opening of the path through the ringer to ground. The holding circuit for relay 401 at this time is opened at the contacts of relay 522. Relay 401 in releasing removes the operating ground from the relay 5|5 and the associated relays and consequently prevents relay 522 from again operating. Should the subscriber answer during the silent period no release operations are possible since relay 401 will still be maintained operated due tothe released condition of relay 522 which maintains the holding circuit for this relay and not until ringlng is applied will ringing be discontinued. Thus the ringing will be tripped only during the ringing period. However, the calling and called subscribers will be able to talk before the ringing is tripped and no loud clicks will be caused by the tripping although the transmitter current will temporarily be less than normal as the resistance of the windings of the repeating coil 52| through which ringing is transmitted to the line will be in series with the talking battery supply circuit until after the ringer is tripped. The talking current supply is through the windings of relay 408. As 401 releases the common holding ground at contacts of relay 409 is removed causing the release of relays 40E, 42|, 420 and 416.

What is claimed is:

1. In a telephone system, a cross bar switch, lines terminating in said switch, single-ended links terminating in said switch, means responsive to the seizure of a calling line for connecting it to an idle one of said single-ended links, and means responsive to designation signals received over said calling line and connected link for connecting said link to a called line.

2. In a telephone system, a cross bar switch, lines each terminating in -contacts in a single row in one coordinate direction oi said switch, links each terminating in contacts in a single row in the other coordinate direction of said switch, means responsive to the seizure of a calling line for establishing a connection through the contacts at the intersecting point of said line and an idle link, and means responsive to dial pulses received over the calling line and the associated link for establishing a connection through the contacts at the intersecting point of said called line and said seized link.

3. In a telephone system, a cross bar switch, lines each terminating in contacts in a single row in one coordinate direction of said switch, links each terminating in contacts in a single row in the other coordinate direction of said switch, a source of current associated with each link, means responsive to the seizureof a calling line for establishing a connection between said line and an idle link through contacts at the intersecting point of said line, and link means responsive to dial pulses received over said calling line and the connected link for establishing a connection between said link and a corresponding called line through contacts at the intersected point of said called line and said link to complete a, talking circuit over said seized link between said calling line and said called line with said source of current associated with said seized link serving as a common talking battery source.

4. In a telephone system, a cross bar switch, lines terminating in said switch, a, single-ended link terminating in said switch, means responsive to the seizure of a calling line for connecting it to an idle link through said switch, means responsive to dial pulses received over said calling line and connected link for connecting said link to a called line, a relay in each of said links, means responsive to the seizure of said called line for transmitting ringing current to said called line and for operating the relay in the connected link, and means operative when the subscriber of the called line answers the ringing for releasing said relay to discontinue said ringing.

5. In a telephone system, a cross bar switch, lines each terminating in said switch inline contact in a single row in one coordinate direction, links each terminating in said switch and link the contactsy in asingle row in the other coordinate direction, a source of current associated with each1inkmeans responsive to the seizure of to transmit, ringingsignals'tofthe calling line, a

relay in said seized link operative in response to said ringing signals means operative when the called subscriber answers for releasing said relay, and means operative on release of said relay for causing ringing signals to cease and for connecting said source of current across the conductor of said link to serve as a common talking battery for both parties.

6. In a telephone system, a cross bar switch having select bars arranged in one coordinate direction, a select magnet for each bar, hold bars associated in the other coordinate direction, a hold magnet for each hold bar, contacts at the intersecting point of said bars, a telephone line terminating in contacts controlled by each hold bar, a link circuit terminating in the contacts controlled by a select bar, means responsive to the seizure of a telephone line for actuating a select magnet of an idle link circuit and the actuation of the hold magnet associated with the callin-g telephone line to establish connections between the calling telephone line and said link circuit over the contacts at the intersecting point of the actuated bar and for thereafter releasing the actuated select magnet, and means responsive to impulses received over said calling telephone line and connect link circuit for reoperating associated select magnets and for actuating the hold magnets of a desired called telephone line for establishing a connection between said called telephone line and the seized link circuit over the contacts at the cross-point of the associated select bar and hold bar.

7. In a telephone system, a cross bar switch, lines terminating in said switch, single-ended links terminating in said switch, means responsive to the seizure of a calling line for connecting it to an idle link, means responsive to impulses received over said calling line and link for connecting said link to a. corresponding called line, means responsive to the seizure of the called line for transmitting ringing current over one of the line conductors ol' the called line, and means operative when the subscriber of said called line answers the call for discontinuing the transmission oi said ringing current.

8. In a telephone system, a, cross bar switch, lines terminating in said switch, single-ended links terminating in said switch, means responsive to the seizure of a calling line i'or connecting it to an idle link, means responsive to impulses received over said calling line and link for connecting said link to a, corresponding called line,

an alternating current responsive relay in each link circuit, means responsive to the seizure oi said called line for transmitting alternating current signals over one of the line conductors of the called line to said associated relay to cause said relay to operate and to signal the subscriber of said called line, and means roperating when the subscriber of said called line answers the call for transmitting the ringing current to said associated relay to cause it to release, and means responsive to the release of Vsaid relay for discontinuing the transmission of ringing current over said called line.

9. In a telephone system, a cross bar switch, lines terminating in said switch, links terminating in said switch, each line having access to each l0 link through a single set of contacts in said cross bar switch, means responsive to the seizure of a calling line for connecting it to an idle link through the associated set of contacts, and means responsive to designating signals received over 1,

said calling line and the connected link for 'connecting said link to the corresponding called line over the associated set of contacts.

10. In a telephone system, a cross bar switch, lines each terminating in contacts in a single row in one coordinate direction of said switch, links each terminating in contacts in a single row in the other coordinate direction of said switch so that each link has access to each line through the contacts at the single intersecting point of said coordinate rows of contacts, means responsive to the seizure of a, calling line for establishing a connection to an idle link at the corresponding single s'et of contacts, and means responsive to dial pulses received over the calling line and the connected link through the associated set of contacts for establishing a connection to a called line between said link and said called line at the corresponding single set of contacts.

HENRY H. ABBOTT. HENRY M, BASCOM.