US2100523A - Automatic telephone system - Google Patents

Description

1937- N. H.-SAUNDERS El AL 2,100,523

AUTOMATIC TELEPHONE SYSTEM Filed Dec. 16, 1955 s sheets-sheet 1 INVENTORS NORMAN H.. SAUNDERS PIEI2 BAKKER ATTORNEY,

3 Sheets-Sheet 2 NIH. SAUNDERS ET AL AUTOMATIC TELEPHONE SYSTEM Filed Djec.

Nov. 30, 1937.

J8 f: 62 L L 323 .IJL L $2: $2:

, INVENTORS NORMAN H. SAUNDERS ATTORNEY.

I PIER BAKKER Nov. 30, 1937.

N. H. SAUNDERS El" AL 2,100,523

AUTOMATIC TELEPHONE SYSTEM Filed Dec. 16, 1935 3 Sheets-Sheet a ATTORNEY.

Patented Nom -'30, 1937 I I if UNITED STATES PATENT OFFICE Norman H. Saunders and Pier Bakker, Chicago,

Ill., assignors, by mesne assignments, to Assoelated Electric Laboratories, Inc., Chicago lllo a corporation of Delaware Application December 16, 1935, serial No. 54,637

is Claims. (01. 179 17) The present invention relates in general to closes a 'circuitfor slow-actingrelease'relay 6. automatic telephone systems and more in par- Relay 6, on energizing, Shifts the test conductor ticular to small automatic systems which are 42 from the cut-ofi relay 4 to ground, thereby adapted for use in rural communities. The obmaking line I busy. f I

5 ject of the invention may be stated to be the Having listened in his receiverto make sure 5 provision of a new and improved system of this hat his li e is ncti se by another Party On character. the same'line, the subscriber at station A will The complete system as installed comprises now dial the first digit of the desired number. nine subscribers lines and. two trunk lines. The s a e ult he d al ng C c s interrupted subscribers lines may be party lines andthe stamomentarily' s'even times at the callingdevice 1 tions are of the local battery magneto type. CD, and the line relay'5fa1ls back seven times, Each station has a dial or calling device. The r lay 6 mainin ene z d due to its being sl w trunk lines provide for interconnection with anacting. On the first deenergization of relay 5' other exchange. Each subscribers line and each a circuit is closed from. ground y- Y' IT,

1 trunk line is provided with an individual relay I8, 26, and wi di s o ys d pa allel type connector, and each connector has access to battery. Relays I and 9 ac o din ly ene to all the lines and trunk lines. and the former relay closes its energizing circuit The automatic switchboard or exchange proper over a new path including contacts 22, so as to therefore consists of eleven relay connectors a n ts uit Closed ifel'elay the busy i when fully equipped. There is also a. storage test relay, should encrgizeand open 6- Re y battery or other source of direct current for oper- 7 s s ow acting d remains Operated '0 e t e ating the relays, and means for supplying ringing described circuit while line relay 5 is responding current and busy signalling current. to the first digit. At 23 relay l closes another The invention and novel features thereof will 'f ay 9 so this re y holds D 3180- At be described hereinafter with reference to the I 22' relay 1 sho t circnitszthe o d n which is 25 accompanying drawings, which Sh w by ea of in series 'with the left-hand windings of the rethe usual circuit diagrams sufficient of the equip- Beating 00i1- This Operation a the e ect of ment involved to enable an adequate explanation including the line conductor-3 in the dialling cirto be made. cult in parallel with line conductor 2. Relay 9 0 Referring to the drawings, Figs. 1 and 2 show p pa s a ir uit f r th usy t st r lay 8' at the complete equipment for one subscribers'line 3 a d at 3 p s do e ringing maof the system. A subscriber's line and one stachine Start d RM thereby Starting p the tion thereon is shown at the leftof Fig. 1, and n n hin V i a a is labeled LINE l. The remainder of Fig. 1 On its first ideen'ergization linerela'y 5: also as and Fig. 2 show the relay connector which is closes a circuit from ground by W yindividual to line I. There is also indicated at '18, 26, and 2, 39 5. I 5, and upp winding of I the right of Fig. 2 several stations on line I and relay l08'to battery. Relays I01 and I08 are the V the connector I63 individual to that line.- Fig. se-cal edod-d and even re ays. used tocontrol 3 shows the ringing machine and the arrangethe-'wunting ys 0n e e i e- 40 ment for generating busy signalling current. lay I08 closes a circuit from ground by W Of 0 The battery symbols shown throughout the draw- I55, 34nd ings will be understood to refer to a single batrelay ml to e y -R y therefore e tery or other source of direct current, erglzes, locks itself at I'5I,and prepares a cir-' It will be assumed now that a, call is to b cult for relay I 02 at I50. It'will be observedalso 425 made from station A on line I to station B on that relay IIH makes atentative selection'of lines 45 line I, the telephone number of the latter sta- I and 6, but the connections closed to these lines tion being 792. When the receiver is removed at are p t other POinilSv and consequently'may station A, a dialling circuit is completed which be neglected at this time, It may be noted, how-' extends from ground at the upper pair of switchever, that the test conductor '42 'of line I is p hook springs by way of the impulse springs of closed through to busy relay 8 and since line I 50 calling device CD, upper ringer magnet, line is usy th ay 8 w ll e n i ed. This d es conductor 2, contact II, a winding of repeating no harm due to theprovision'of contacts '22, as coil R, contact controlled by spring I 2 of relay previously mentioned. 4, and lower winding of line relay 5 to battery. On energizing after its first deenergization, line Y Relay 5 energizes over the above circuit and relay 5 separates springs I I and I8, but armature 55 16 picks up ground at I1 and. thus closes a circuit over 46 for the lower winding of relay I08 which maintains the relay energized. The lower winding of relay I01 is also included in this circuit and relay I01 accordingly energizes. Relay I01 breaks the former operating circuit of relay I08 at H and prepares a holding circuit for itself at the same point.

On the second deenergization of line relay 5, armature I6 disengages spring I1 and the latter again engages spring I8. This recloses the circuit over 45, which now holds up relay I01, and breaks the circuit over 45, which permits relay I08 to fall back. On deenergizing, relay I08 closes a circuit by way of grounded conductor 43, H6, I2I, I35, I44, I50, and relay I02 to battery. Relay I02 energizes, locks itself at I48, opens the locking circuit of IOI at I49, permitting IOI to deenergize, and prepares a circuit for relay I03 at I41. Relay I02 closes connections to lines 2 and 1 but for reasons previously stated these connections may be neglected.

On energizing after the second deenergization, line relay 5 breaks the circuit over 45 and permits relay I01 to fall back. Relay I08 being deenergized, no circuit is closed over 46.

On the third deenergizaticn of line relay 5, a circuit is again closed over 45 for relay I08. On energizing, relay I08 closes the prepared circuit for relay I03. The latter relay energizes, locks itself at I45, unlocks relay I02 at I46, and prepares a circuit for relay I04 at I44.

On energizing again, the line relay 5 holds relay I08 over 46 andenergizes relay I01 over the same circuit, all as previously explained.

On the fourth deenergization of line relay 5, relay I01 is held over 45, while relay I08 is allowed to fall back, closing the circuit for relay I04, previously prepared by relay I03. On energizing, relay I04 locks itself at I40, unlocks I03 at MI, and prepares a circuit for relay I04A at I39.

On the next energization of the line relay, the circuit over 45 is broken and relay I01 falls back. Relays I01 and I08 are both deenergized now.

On the fifth deenergization of line relay 5, a circuit is closed over 45 for relay I08, which operates and closes the previously prepared circuit for relay I04A. On energizing, relay I04A locks itself at 50%, breaks the chain to relay illl at 565, and closes a circuit for relay I05 at I61. On energizing, relay I05 looks at I36, opens the locking circuit of I04 at I31, and prepares a circuit for relay I06 at I35.

On energizing again, the line relay5 closes a circuit over 46 which holds relay I08 and operates relay I01.

On the sixth deenergization of line relay 5, the circuit over 48 is broken, allowing relay I08 to fall back, while relay I01 is held over 45. On deenergizing, relay I08 releases relay I04A, and closes a circuit for relay I06, previously prepared by relay I05 at I35. Relay I 06 energizes and looks at I24, also breaking its initial energizing circuit at I23. Relay I06 is a reflexing relay, which provides for using the counting chain IOI-I05 over again to count the digits 6 to 0, this being accomplished by shifting the test lead 44 and talking conductors 41 and 48 from their normal association with lines I,-5 into association with lines 69 and the two trunk lines.

In addition to theforegoing, relay I06 re-' verses the connections between the contacts at H6 and the two operating leads extending to the counting chain, the same being effected at HI and I22. Since relay I08 is now deenergized a circuit is closed from the grounded conductor 43 by way of H6, I.2I, I39, I65, I43, I41, and relay IOI to battery. Relay IOI energizes, looks itself at I5I, breaks the locking circuit of I05 at I52, and prepares a circuit for I02 at I50.

On the next energization of line relay 5, the circuit over 45 is broken and relay I01 falls back.

On the seventh and last deenergization of line relay 5, a circuit is closed over 45 for energizing relay I08, which operates and closes the previously prepared circuit for relay I02, it being recalled that relay I06 is now locked up so that the circuit is completed over 43, H6, I22, I35, I44, and I50 to I02. On energizing, relay I02 locks itself at I40, unlocks relay I0! at I40, and prepares a circuit for relay I03 at I41. This latter circuit, of course, is of no interest in the present case, since the last deenergization of the line relay has occurred.

The line relay energizes again after the final deenergization and comes to rest in energized position. Relay I08 is accordingly held over 46 a and relay l01 is energized. These relays, however, have no further functions to perform.

It will be recalled'now that relays 1 and 0 are maintained in energized position while the line relay is responding to the first digit. This is due to the fact that relay 1'has its circuit closed on each deenergization of the line relay and being slow acting is able to stay in operated position, holding relay 9 energized by way of 23. When the line relay comes to rest, however, relay 1 receives no more impulses and shortly falls back. Before this occurs a test is made of line 1, which has been selected by relay I02.

The rectangle i63 represents the relay connector individual to line 1 and test conductor E52 corresponds to test conductor 42, Fig. 1. It will be seen that if line 1 is idle the conductor E52 will extend through to the cut-off relay in the connector I63 while if the line is busy the conductor I52 will be grounded. If busy due to the line being in calling condition, the test conductor will be grounded at contacts such as l0, as already explained, while if the busy condition is due to the line having been called by another connector the test conductor will be grounded at contacts such as 4i of such other connector.

Assuming new that line 1 is busy when called, the test relay 8 is energized over a circuit which extends from the grounded test conductor E62 by way of I54, I18, 44, contacts controlled by 4|, 33. (relay 9 is still energized), and winding of test relay'8 to battery. On energizing, relay 8 grounds the busy start lead EST at 28, prepares a locking circuit for itself at 21, opens the initial energizing circuit of relay 1 at 26, and connects the busy tone lead BT to the talking circuit at 25, Relays 1 and 9 new fall back and test relay 8 is locked up over 21 to ground at 20.

The grounding of lead EST energizes relay 202, Fig. 3. On energizing, this relay'closes a circuit for its upper winding and since the windings are in opposition the relay falls back and opens the circuit of its upper winding, whereupon it again energizes- Thus relay 282 operates as a buzzer while conductor BST is grounded. Relay 20I, which short circuits itself on energizing, also operates as a buzzer, but at a very much slower speed due to being slow to energize also slow tofall back. The operation of relay 202 rapidly changes the potential at 203 and thus produces a tone current on conductor ET. This conductor is interrupted at regular intervals by relay 20I to give the calling subscriber the characteristic busy signal. 204 is a radio frequency choke-coil.

On hearing the busy signal the calling subscriber will hang up his receiver. This breaks the dialling circuit at the switchhook springs and the line relay 5 falls back, followed by release relay 6. The falling back of relay 6 breaks the locking circuit of any relays that may be energized at this time and the connector is thus restored to normal.

It will be assumed now that line i is idle when called. This being the case, no ground is found on conductor I62 when the busy test is made and relay 8 is not energized. Whenrelay 9 falls back a circuit is closed for relay I0 whichextends from ground at 20, by way of 21, lower winding of i0, 33, contacts controlled by 4d,.

5 i0, 154, IE2, and winding of the cut-off relay (similar to 4) of the called line. The cut-off relay energizes and disconnectes the line relay at contacts corresponding to II and I3, Fig. 1. Relay I0 also energizes and locks itself at 20. Relay Iii grounds the test conductor I62 at M, opens the conductor 45 at 30, opens conductor 43 at $9, closes points in. the talking circuit .at 35 and 3.8,and prepares the rin ing circuit at 3?. Relay I09 energizes in parallel with the upper winding of relay I0. Relay I09 prepares a circuit for relay I70 at I28, and shunts contacts II and I3 of relay 4 at I27 and I32. Relay ltfi also closes certain contacts I23, I29, I30, and lti, which would be included in the talking circuit if lines such as line 2 or line 5 had been called. The purpose of these contacts is to prevent the possibility of momentarily connecting together two lines such as line I and line 2 while the counting relays are operating. Relay lfil, for instance, connects up line i and relay I02 connects up line 2 and breaks the circuit of IOI, from which it follows that line 2 is connected up before line I is disconnected. This does no harm, however, because of the insertion of contacts I2! and I23 which are open at the time the counting relays are operating.

Relay I09 also places a ground on the ringing machine start conductor RMST at I33. This conductor, it should be stated, is first grounded at 32 by relay 9 when dialling begins, the object being to get the ringing machine in operation so that it will be ready for use upon the dialling of the second digit, which is a ringing digit. When conductor RMST is grounded, the start relay 205 is energized. This relay is slow acting so that it holds up during the slight interval betweenthe falling back of relay 0 and the pulling up of relay I 09.

On energizing, relay 206 closes a circuit for the vibrator magnet 209, which'attracts the vibrating element 2I0 with considerable power, so that no time will be lost in building up the proper amplitude of vibration. Relay 205 also closes a circuit for slow-to-energize relay 201. When this relay operates it inserts a resistance in the circuit of magnet 209, and closes a circuit over which the magnet short circuits itself through element H0. The vibrator now starts operating at normal amplitude, magnet 209 alternately attracting and releasing element 2J0. Relay 20? also closes a circuit for relay 203 which is slow to energize due to its normally short circuited lower winding. Relay 208, on energizing, connects the vibrator contacts through to the primary winding of transformer T. The delay introduced by relay 208 is desirable to prevent possible welding together of the vibrator contacts on starting, which is especially liable to happen in thecase of'the left-hand pair of contacts. The

device enclosed within the rectangle 2! I isa suppressor of radio frequencycurrents.

Having selected the desired line by dialling the digit 7, thecallingsubscriber can now proceed with the dialling of the remaining digits of the number, which will be effective to promote the ringing operation. The desired station on the line is signalled by code ringing, and the code of such station is one long ring and one short ring. This code is produced by dialling the final digits 9 and2 of the. called number," as will now be ex-' plained.

When the digit 9 is dialled the line relay 5 falls back nine times and sends nine impulses to relays and 9, which pull up andhold on throughout the series of impulses .as. previously; explained; 'If relays I01 and. I08 are in energized position, as they are inf the instant case, they Line relay, 45 is open at 39. The falling back of lllifcauses no further action at the counting chain because 33 is open at 49. Relay 9 closes the ringing circuit in an obvious manner at 30 and 31, produce ing a long ring onthe called line.

When the digit 2 is dialled, the line relay 5 controls the relays I and 9 the same Way, except that these relays are held up only for the duration of two impulses instead of nineimpulses, which produces a short ring on the called line. r

The telephone at station B may be the same as the telephone at station A, and it Will be seen therefore that when the receiver is removed both sides of line I will be grounded through the ringer magnets, calling device, and switchhook contacts. This closes a simplex circuit for energizing relay I10, which was connected up to the junction of the right-hand windings of repeat-' ing coil R by relay-I09. On energizing, relay I70 closes a circuit for the upper winding of relay 6,

The opening of contacts II and 26, and thereby prevent further "operation of these relays such as would occur if another digit 20 both fall back onthe first .deenergizationo'f the f l0! not being able to hold upbecause should be dialled at station 'A, or if the dial- .should be accidentally disturbed suflicient to operate the calling device. {The locking up of relay 8 also prevents the operation of relays l and 9 when the receiver is hung up at station A.

The desired connection has now been estab lished and the subscribers can engagein conver sation. The talking circuit is shown in heavy lines and may be readily "traced. The calling station is connected to the left-hand windings of repeating coil R over conductors 2 and 3. and through contacts of relay I09. windings of the repeating coil are connected to the called station through contacts of relays 9, l0, I06, and, I02, and over conductors Hi0 and NI. When the subscribers are through talking they will hang up their receiver's. mentof the receiver at station A breaks the circuit of, line relay 5 which falls back. and breaks The replace-.

The right-hand vious, for instance, that if the subscriber at station A had dialled the digit 3 instead of the digit 7 he would have selected line 3 by means of counting relay I03. Relays IOI to I05 select lines I to 5 responsive to digits 1 to 5. On digits 6 to 9 the counting relays IOI to I04 select lines 6 to 9, due to the operation of relay I06, which energizes whenever a digit greater than the digit 5 is dialled. On the digit the counting relay I selects the first trunk line.

There are two trunk lines and provision is made for automatically selecting the second trunk line if the first is busy. Explaining how this is done, when the subscriber at station A dials the digit 0 the connector operates as previously described except that the counting proceeds for ten deenergizations of line relay 5, resulting in the energization of relay I05 on the tenth deenergization. On energizing, relay I05 looks itself at I36, breaks the locking circuit of I04 at I31, and prepares a circuit for H0 at I38. Relay I05 also selects the first trunk line at I89, I90, and I9I, since relay I06 is now energized.

If the first trunk line is busy there will be a ground potential on test conductor I82, and test relay 8 will energize over a circuit including ground at I82, I88, I9I, H9, 44,. 33, and winding of. relay 0 to battery. Relay 8 having energized and relay I04 having deenergized, a circuit may be traced from ground at 2I by way of 24, 28, I25, I42, I38, and winding of relay IIO to battery. On energizing, relay IIO locks itself at I34, and at I86, I31, and I88 substitutes the second trunk for the first. If the second trunk is busy the busy test relay 8 will be held up from ground on test conductor I85 of the second trunk, and when relays 1 and 9 fall back, the busy test relay 8 will stay locked up and will give the calling subscriber a busy signal. On the other hand, if the second trunk is idle there will be no ground on test conductor I85, and the busy test relay 8 will fall back as soon as the switch is made from the first trunk to the second. Then when relays 1 and 9 fall back a circuit will be closed for relay I0 which operates and closes the connection through in the manner previously explained. It will be understood, of. course, that if the first trunk is idle when called the test relay will not energize and no circuit will be completed for relay IIO, so that the first trunk will be taken for use.

As stated before, each trunk line is equipped with an individual relay connector which is the same as the connector shown in the drawings. The connector for trunk I is indicated in the drawings at I92. The trunk lines extend to an operators position at adistant exchange, where they terminate in jacks and suitable associated equipment. Each trunk may terminate, for instance, in a trunk circuit such as the trunk circuit T65 which is shown in Fig. 6 of Patent No. 1,772,690, August 12, 1930. I

Assuming now that the subscriber at station A has operated the connector shown to establish a connection with the first trunk line, the cut-off relay in the connector I92 will be energized to cut off the line relay. The trunk number will include a ringing digit, the complete number being 05, for instance, and when the last digit 5 is dialled ringing current will be transmitted over trunk conductors I80 and I8I to operate a ringup relay in'the trunk circuit at the distant end, which locks and brings in the line lamp. When the operator plugs in to answer, the lamp is extinguished and a grounded simplex circuit is established over the two trunk conductors I80 and I8I in parallel, energizing relay I10 of the calling connector with results previously explained. The ground connection for the simplex circuit includes a marginal supervisory relay which cannot energize in series with relay I10, the latter being of high resistance. The marginal supervisory relay remaining unoperated, the supervisory lamp in the operators cord circuit remains dark, indicating the continued presence of the calling party'on the line.

The desired connection is now completed by the operator. When the calling party at station A is through talking he will replace his receiver, releasing the connection to trunk I. The deenergization of the cut-off relay in connector I92 thereupon restores the normal connection of the trunk conductors I80 and I8I to the line relay of the associated connector I92. The lower winding of the line relay (similar to 5) is of relatively low resistance and the distant supervisory relay now energizes, lighting the supervisory lamp in the operators cord and informing the operator that the calling party has hung up.

If the operator at the distant exchange should desire to call a station such as B, she will plug into one of the trunk lines, trunk I for instance. As before mentioned the art of plugging in cornpletes a grounded simplex circuit, which in the present case will energize the line relay of the connector I62. The lower winding only of the line relay is included in the circuit and the marginal supervisory relay therefore energizes, lighting the supervisory lamp in the operators cord circuit. The number is now dialled and the connection completed in the manner described. When the called party answers the relay in connector I92 which corresponds to relay I'zIl is energized, energizing in turn the cut-off relay such as 4, which inserts the high resistance upper winding of the line relay in series with the lower winding. This causes the distant supervisory relay to fall back and put out the supervisory lamp. When the called party hangs up the relays such as I10 and 4 fall back again, the upper winding of the line relay is cut'out, the distant supervisory relay pulls up, and the supervisory lamp is lighted again.

The foregoing brief explanation o-fthe supervision on trunk calls has been given so that the reason for the high and low resistance windings of the line relay and for the high resistance relay I10 may be understood. As regards the latter relay it may be pointed out further that although this relay could theoretically be eliminated by connecting the junction of the right-hand repeating coil winding direct to the upper winding of relay 4 by way of I20 and making the upper winding of relay 4 a high resistance winding, this would not be practical because of the number of contact springs on relay 4. It will be understood that these supervisory features are not involved on local calls. On a call from station A to station B, for instance, the insertion of. the high resistance winding of the line relay 5 in the dialling circuit when the called party answers has no particular function, although conceivably this operation could be made to control some substation device such as a coin collector. However this may be, it is desirable in any event to have the connectors in a given exchange all alike for various reasons, and especially for-convenience of maintainance.

If the subscriber at station A should desire to call another station on his own line, he can do this by operating his magneto, or hand generator, code ringing the wanted station in the well known manner. There is a. condenser inserted between the left-hand windings of the repeating coil R at the connector to avoid placing a heavy shunt on the generator. The removal of the receiver at station A of course operates line relay 5, which operates release relay 6, and the line is made busy by grounding conductor 42 at l9.

Itwill be clear that the relay connector herein disclosed can be readily modified for use in a ten line isolated exchange. Line ll] would be connected up at. contacts, I89, I99, and I9! of relay I05 and relay Ill] would be omitted, as well as the circuits for operating it. The supervisory arrangements could also be left out, that is, relay lfi5 could be a single wound relay, contacts :2 could be left out, and relay I10 could be omitted, since the upper winding of relay 4 would not have to be of high resistance. The connector therefore would be considerably simplified over the one shown herein.

The invention having been described, what is a considered to be new and is desired to have protected by Letters Patent will be set forth in the following claims.

What is claimed is:

1. In a telephone system, a subscribers line, a relay connector individual to said line, a chain of counting relays in said connector controlled by digit impulses received over said line, contacts on each counting relay for selecting two other lines, and means controlled in accordance with the value of the digit received for making a selection between the two lines selected by any counting relay.

2. In a telephone system, a subscribers line, a relay connector individual to said line, other lines, means including counting relays in said connector for connecting said first line to any one of said other lines, means for controlling said counting relays by transmitting digit impulses over said first line, and ringing means responsive to additional digit impulses transmitted over said first line, and means for preventing the said counting relays from responding to the impulses which control the said ringing means.

3. In a relay connector, a chain of counting relays under dial control for selecting and extending talking connections to a plurality of lines,

' means for operating any counting relay once or twice depending on the value of the digit dialled, a series of lines arranged to be selected by said relays on the first operation thereof, and a second series of lines arranged to be selected by said relays on the second operation thereof.

4. In a relay connector, a chain of five counting relays for selecting and extending talking connections to a plurality of lines, means for controlling said relays to count the impulses in any digit from one to five, or to count the impulses in any digit from six to naught by reoperation after five impulses have been counted, two groups of lines to which connections are extended by said relays, and circuit arrangements whereby the group in which a line is selected depends on whether or not the controlling digit is greater than five.

5. A reflex counting relay arrangement comthan the maximum number 7 V counted, means for operating and reoperating.

' ing to impulses, a busy test relay prising a chain of counting relays less in number certain or all of said relays responsive to a series of impulses containing more impulses than there are relays, and circuit arrangements whereby the relays which "count the odd impulses the first time they are operated count-the even impulses on reoperation and whereby the relays which count the even impulses the first time they are operated count the odd impulses on reoperation.

6. A reflux countingrelay arrangement com-' of impulses to be prising a chain of counting relays, a control re-.

lay energizing on the odd impulses of a series to be counted and deenergizing on the even impulses, two control conductors leadingfrom front and back contacts, respectively, of said control relay to saidcounting chain, circuits for energizing the odd relays of said chain over one control conductor and the..even relays over the other control conductor, and circuit arrangements such I that when the number of impulses already counted equals the number of counting relays the next impulse will cause the said'control conductors to be reversed with respectto said control relay contacts. V

7. In a relay connector, a chain of counting relays'for selectingand completing talking connections to lines, means for operating said relays successively responsive to dialling operations, circuits such that the operation of any relay except the first causes the release of the previously operated relay, whereby upon the completion of a dialling operation only one relay will remain energized, and nection of lines associated with adjacent relays during the interval that such relays are both in operated position.

8. In a telephone system, a subscribers line, a

calling device at the station on said line, line conductors, and a line relay at the exchange, a control circuit including said calling device, a single one of said conductors, and said line relay, and means at the exchange. responsive to operation of said calling devicefor converting said circuit into a simplex circuit comprising both conductorsof said line.

9. In a telephone. system, a local battery magneto party line, a directively controlled switching device individual to said lineat the exchange, a repeating coil associated with said line at said means for preventing the intercon-- device, a control circuit for said device normally including only one. side of said line and one winding of said repeating. coil, there being a condenser inserted between the'line windings of said coil to increase theimpedance thereof to magneto ringing current, and means for short circuiting said condenser the line in said control circuit when the same is used to directively control said device. 7

10.In a connector, a line relay, a slow acting relay energized by said line relay While respondcontrolling the circuit of said slow acting relay,

ergizing said busy relay or not depending on to include both sidesof;

means for enwhether or not a called line with which connection is established by said connector is busy, ringing -means controlled by said line relay and slow acting relay if the called line is idle, and

means for operating said busy relay when the.

called party responds for preventing further energization of said slow acting relay under control of said line relay. 7

11. A relay exchange comprising subscribers 'lines and a trunk line, a relay connector individual to each line, a line relay in each connector having a low resistance winding controlled over the two sides of the associated line in parallel,

an answering relay in each connector having a' high resistance winding controlled over the two sides of a called line in parallel, and means effective responsive to the operation of the answering relay in any connector for inserting a high resistance in series with the line relay of such connector. V

12. In a relay connector, an incoming line, a plurality of outgoing lines, a chain of counting relays, means for energizing a variable number of said relays successively by digit impulses transmitted over said incoming line to select and connect a desired outgoing line to said incoming line, each counting relay having contacts for connecting a difierent outgoing line to said incoming line, another outgoing line alternative to .a particular one of said first mentioned outgoing lines, means including a relay effective in case said particular outgoing line is busy when connected up by the associated counting relay 'for switching the connection to said alternative outgoing line, and means for locking the concerned counting relay to maintain the connection.

13. In a relay connector, an incoming line, a plurality of outgoing lines, including two trunk lines, a chain of counting relays for connecting said incoming line to said outgoing lines, including one counting relay common to said trunk lines, a trunk switching relay, and means for operating said connector by impulses over said incoming line to connect the same with either one of said trunk lines through serially related contacts on said last mentioned counting relay and said switching relay.

NORMAN H. SAUNDERS.

PIER BAKKER.

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