US2289505A - Telephone system - Google Patents

Description

Jul -14, 1942. KU H'L Y 2,289,505

TELEPHONE SYSTEM Filed May 27, 1959 4 Sheets-Sheet 1 E awavrom JOSEF Kym/45y ATTORIVE y 1 19 2- J. KUCHLEY 2,289,505

TELEPHONE SYSTEM INVENTOR: JOSEF Kl/CHLEY BY; M

A TTORNEY.

Patentecl July 14, 1942 UNITED STATES PATENT OFFICE TELEPHONE SYSTEM Application May 27, 1939, Serial No. 276,139 In Germany May 30, 1938 11 Claims.

The present invention relates to automatic telephone installations, in which a group of subscribers is connected to an exchange by one single connecting line.

In known systems of thistype it is necessary, in order to establish a connection between two subscribers of such a group, either to establish and to maintain a connecting path which extends over all or part of the digit impulse receivers, at the exchange, used for connection with other groups of subscribers, or to arrange special discriminators, consisting of groups of relaysor of step-by-step switch mechanisms, associated with a connecting path seized by a call from one of the subscribers or the common junction line of the groups of subscribers. after selection of the marking digit of the group of the ringing subscriber, switch the connection to the special switching apparatus used for establishing and maintaining internal connections. These known arrangements are in many cases uneconomical, particularly if internal connections between the subscribers of a group are relatively rare. The present invention discloses an economical and, at the same time, perfectly reliable manner of establishing connections between two subscribers of a group of subscribers which is connected to an exchange by a common junction line. According to the invention the selection of the marking number for connections between two subscribers of the group (internal connection) causes a selector arranged for communication with other subscriber groups of the installation to effect, at a point of the connection path preceding the group selector, the connection to the connection path of a switching mechanism (revertive call transmitter) utiised only for establishing and maintaining internal connections.

The drawings illustrate, by way of example, two embodiments of the invention, all the switching means and circuits which are not necessary for explaining the invention having been omitted.

The embodiments illustrate the internal connection for two-conductor junctions. The group of subscribers which is connected to the exchange by a common connecting line may consist of more than two subscribers. The invention is therefore applicable to party lines having a greater number of branch stations and for group stations. In these instances the switch mechanisms (revertive transmitters) which, in accordance with the invention, are arranged to be switched into use for internal communication are merely associated with switching means These discriminators,

which, under the control of the calling subscriber, effect the selection of the desired branch station (of party lines) or the desired group station subscriber.

Fig. 1 illustrates the circuit arrangement of two subscribers stations (two-conductor junction) forming a group which is connected to an exchange by a common junction line (party line) and the preselector associated in the exchange with the common junction line.

Figs. 2 and 3 illustrate a path to a group selector IGW to which a switching mechanism for internal connections (revertive transmitter) may be connected by a service selector. This embodiment requires the selection of a one-digit marking number for initiating internal connections.

Figs. 4 and 5 illustrate'a further embodiment, wherein a marking number comprising a plurality of digits must be selected for initiating internal connections. a two-digit marking number being assumed. Figs. 4 and5 illustrate only the access means toa first group selector, reached over a preselector, and a revertive transmitter RUZ adapted to be connected to this access means. The wiring of the subscriber stations and the associated preselector in the exchange to the party line corresponds to that shown in Fig. 1.

I. EMBODIMENT Accoanmc T0 Freumcs 1, 2, AND 3 1. Internal connection, the subscriber Tnl making a call The subscriber Tnl removes his receiver, closing the following call circuit: earth winding I of the startrelay El, subscribers station, choke Drl, conductors Zal, la, contact ltl, winding I of relay RI, The relays El and RI operate. The relay El controls'the blocking circuit which includes the condenser KI and the choke Drl, and which prevents overhearing or cutting in on an existing. connection when the party line is engaged,and over which the subscriber Tnl is connected to its conductor la! and, thence to the conductor la of the party line. At the contact 2el the choke Dr! is short-circuited. Contact 3e] opens and breaks the direct earthing to the condenser KI, earth being now connected to the condenser over the winding II of the start relay El, establishing the symmetry of the subscribers conversation loop; At the contact 4el the subscriber Tnl is connected to his secondconductor lbl and, consequently, to the second conductor of the party line.

lntheexchange, the relay RI closes the-cir- .means, and A2, in the group selector.

cuit of the rotary magnet D of the preselector VW, at the contact 514 wiper 6, rest contact 'I of the preselector, contacts 5H, 8H, rotary magnet D, interrupter RU, The preselector leaves its rest position, the wiper 6 passing on to the contact segment I I, over which the circuit of the rotary magnet extends, independently of the contact 5H By opening contacts I2rI and I3rI and closing contacts I4rI and IErI the relay RI has, moreover, crossed over the conversation conductors. Whether the conversation conductors remain crossed after the preselector is set on an extension line, depends on which of the two subscribers is calling. As the call is initiated by the subscriber TnI, the line connections are subsequently reversed again, the meter ZI is again connected at the contact ISrI and meter Z2 is again disconnected at the contact IIrI. At the contact I8rI the connection of a winding III of relay RI is prepared.

When the wipers of the preselector reach the contacts of a connecting means I8, I9, to a free group selector, the test relay TI operates in series with the seizing relay CI of the group seby it the group selector IGW are locked against The contacts seizing by any other preselector. ItI, 2425i open and cause the ringing coils I and II of the relay RI to be disconnected, and at the contacts tI, 26tI the talking conductors are switched through. At the contact 21tI the highresistance winding III of relay RI is connected to the locking circuit. The winding III is a differential winding to winding I. The relay RI is restored and its contacts are restored to the positions illustrated in the drawings. The crossing of the conversation conductors is reversed, and the meter ZI of the subscriber T'nl is again in parallel with the locking winding II of relay TI.

The group selector IGW is equipped with two different access means. Over the line I 8, I9, 20 this group selector can be engaged only by preselectors of two-conductor junctions, while it may be seized over the access 28, 29, 30 by preselectors of connection lines of other subscribers, for example single line subscribers.

Switching means are arranged in th access means I8, I9, 20 which permit the normal operation of the group selector when engaged by a two-conductor junction line. The microphone feeding circuit for a subscriber in a two-conductor junction line passes, contrary to that of a single-line-subscriber, only over a talking conductor (I8). and the relays AI, in the access The bridge relay B2 in the group selector is connected by the relay AI at contact 3IaI: choke Dr3, contact 3IaI, relay B2, At the contact 32aI the relay OI is put under the control of the ofi' normal contact 33kgw, which, however, is closed only on the selection of a special marking digit, for example 0.

In order to provide a connection with the subscriber TnZ of the two-conductor junction, the subscriberflnl must select-a special marking digit, for example 0.

The contact 33kgw in the group selector is then closed. If another cipher for example 3 is to be used as a marking digit for internal connections instead of 0, a contact of the control relay which is only energized during transmission of current impulses is connected in series with the contact 33kgw, in order that when the contact 33kgw is temporarily closed, during the setting of the group selector by a current impulse series comprising more than three impulses, the relay OI in the special access means to the group selector will not be energised and induce a service selector of a free revertive transmitter to operate.

When the marking digit for internal connections is transmitted, the relay OI operates as follows: relay OI, contact 320A, conductor ZclI, contact 337C911), The start relay AnI of the service selector DWI of a free switching mechanism (revertive transmitter RUI provided for the two subscribers of a two-conductor junction, is energised: contacts 59t2, 5IoI, 52pI, resistance 53, relay AnI, The rotary magnet DI of the service selector DWI is connected over contact 54anl. The service selector makes one step. At the contact 550 the relay AnI is shortcircuited; is de-energised and disconnects the rotary magnet D I. The alternate reciprocal connection and disconnection of AnI and DI continues until the test wiper 56 of the service selector is connected with the access means I8, I9, 20 since then the following test circuit is completed: relay T2, contacts 5'I0I, 58, wiper 56, windings I and II of relay PI, contact GIIhI, Contact 6| pl opens and arrests the service selector DWI. At the contact BZpI the high resistance winding I of relay PI is short-circuited locking the access means I9, I8, 20 against seizure by another service selector. The relay AnI is disconnected at contact 52pI and the start line is switched through to the next revertive transmitter at contact 63pI. Contact G IpI closes and connects to the conductor 28 over the resistance 65, the wiper 66 and contact 61, establishing a new circuit which holds the relays TI and RI at the preselector energised. Contact 68pl closes and connects the relay A3 to conductor I8 over the wiper 69 and contact I0, so that relay A3 is energised.

In the access means to group selector IGW which has been seized relay T2 is energised. At the contact I lt2 it looks up independently of contact 5IoI, releasing the group selector IGW, which had been seized at the ringing of the subscriber 2nI, by opening contacts 2It2, I2t2 and 13132. The relays AI, A2, CI, B2, OI are restored. The group selector returns into its rest position and can be seized again also during the interval, in which the access I8, I9, 20 is included in an internal connection, as the switching means of the access I 8, I 9, 20 cannot exert any influence on the group selector. The relay A3, energised in the feeding circuit of the subscriber TnI, closes the contact 14113 arranged parallel with contact 60hI in the circuit of the test relay PI, and energises, over contact I5a3, the relay HI which opens contact BOhI. The contact l6a3 is opened preventing a premature short circuit of resistance 65. At the contact "a3 the following ringing circuit is completed: Ringing current source, winding I of relay RaI, contacts 18ml, 11113, wiper I9, contact 80, conductor I9, contact and wiper of the preselector, contacts I3rI, 26tl, conductor Zb, la2, choke Dr2, bell of the subscribers station Tn2, relay E2, earth (-I-). A small portion of the ringing current flows to earth over the condenser K2 and contact34e2. The relay E2 does not chatter, as its winding II is shortcircuited' at the contact 34e2; In the revertive transmitter the relay RaI does not operate.

The calling of the second subscriber of the twoconductor junction therefore takes place automatically, from the revertive call transmitter and without any further selective action on the part of the calling ubscriber.

When the subscriber Tn2 answers the call, relays E2 and Hal arranged in series are energised by the direct current path established at his station. Relay E2 effects the connection to the conductor 2122 and switches over the blocking circuit. At the contact 49e2 the chokeDrZ isshort circuited; and by the opening of contact 34e2 the direct earthing of the condenser K2 is discontinued. Earth is connected to thecondenser K2 over windingII of relay E2. The symmetry of the conversation loop of the subscriber T112 is established. The relay Ral locks up over its winding II at the contact 8I1'aI in acircuit dependent on contact 15413, connects'the potential required for the feeding of the microphone to conductor I9 over choke D14, contacts 82ml, I'Ia3, wiper I9 and contact 80 and disconnects its winding '1, at the contact 18ml. The short-circuit'for resistance 65 is preparedat the contact 83ml.

When at the termination of the conversation, the calling subscriber TnI hangs up, the relay A3 is ole-energised. Contact I6a3 closes and shortcircuits the resistance 65, so that the current in the blocking circuit over the conductor 20 is increased to such an extent that the meter ZI is enabled to operate. At the contacts 15:13 and 14:13 the circuits for the relays Rail, HI, PI, T2 are broken. The relay TZhas a longer delay before release than the relaysRaI and PI, so

that during a short time interval all the contacts fidpl, 83ml and 2It2 which control the flow of current through the conductor 20 are open. The relay TI of the pre-selector, therefore, restores and returns the pre-selector to its rest position.

2. Internal connection, the subscriber T1t2 making a call When the subscriberTn2 removes his receiver,

his start relay E2 operates '-in series with the:

winding II of relay RI earth, winding I of relay E2, subscribers station T112, choke Dr2, conductorsla2, lb, contact 24tI, winding II of relay RI, The relay E2effects the previously described switching over of theblocking circuit and connects the subscriber Tn2 to the conductor- 1122.

The relay RI startsthe pre-selector and effects acrossing of the conversation conductors by opening contacts I2rl, I31-I, and closing contacts I IrI, IrI. over contact I'IrI and disconnects the meter ZI at the contact I61'I. When the subscriber T111 initiates a call, relay RI remains energised during the connection as the winding II of relay RI is Moreover, it connects the meter Z2 contacts I5'1I, 26H, conductor l-b m2; contact conductor.

Mel, subscriber's station T1z2; winding I of relay earth 'Thegroup selector IGW is set in accordance with the marking number for internal connnections. This marking number is the same, for example 0 which the subscriber Tnl must select; inorder to call the subscriber T112. The relay OI is energised and a free revertive transmitter RUI'connected to the access means I8, I9, 20.-

Since the talking line is crossedin the preselector, the ringing circuitpasses over conductor I9, contacts I ITI, 25tI, conductors la, Zal, the bell of subscriber T7, winding I of relay EI earth When the subscriber Tnl answers the call, the ringing current is switched off in the manner described.

H. EMBODIMENT ACCORDING TO FIGURES 1, 4, AND 5 1. Internal connection, subscriber TnZ making a call The subscriber T112 removes his receiver, causing the connection to the conductor Zb2/Za, the switching over of the "blocking circuit and the setting of the pre-selector VW, as described. Relay RI remains energised.

In the feeding circuit the relay A l in the access means to the group selector IGW and in the group selector IGW the relay A5 are energised. on the contact IOIa4 a circuit over choke D1'5, winding II, and relay B5 is closed. At contact mm the condenser K3 and the winding I of the choke Dr5 are connected to the upper talking The circuit over a winding I of relay O2 is prepared at the contact I03a4.

For initiating an internal connection the selection of a two-digit marking number is necessary. The connection of the revertive transmitter RU2 is effected after the emission of a train of current impulses corresponding to the first digit of the marking number, while the release of the group selector IGW and the associated number impulse receiver set by the second train of number impulses is effected only when the second train of number impulses corresponds to the second digit of the marking number for internal connections. Afterterminationof the first train of impulses contact IMkgw is closed and relay O2 is energised: contact loamug, conductor Zd2, contacts H1511, I03a4, winding I of relay O2, Relay O2 closes its contacts H1502, M1602, M1102. The impulse "for connecting 'a free revertive transmitter is transmitted'over: contacts Ill8n, H1502, start conductor I09, wiper I I0, contact III of discriminator' ML, contacts H2122, II3d2, relay A112, At the contact I I4an2 the rotary magnet D2 of the service selector DW2 is connected whereby the circuit of'relay A112 is opened at the "contact I I M2 and the wipers of the service selector DW2 are advanced'by one step. The magnet'D2 is disconnected and the circuit of the startrelay An2 is re-established. The alternate reciprocal connection and disconnection of the magnet D2 and the start relay A112 continues; until the wipers of the service selector DW2 reach the junction of that access means to a "group selector IGW from which the impulse for the connection of the revertive transmitter istransmitted. The relays P2 and N then operate: winding'I of relay N, contacts I0Io2, I I5, wiper'of service selector DW2, windings II and I of 'relay'P2,"contact IIIg, Contact I I8p2 opens and arrests the service selector DW2. The seized a'c'cess"means"is'-1ocked' at'the contact H9112 against seizure'by another service selector by a short circuit of the high-resistance winding I of relay P2. At the contact II2p2 the relay A112 is disconnected and at the contact I20p2 the start conductor I09 is switched over to the start conductor I 2| leading to the next revertive transmitter. Contact I22p2 closes and connects the relay A6 over the wiper I23 and contact I24 of the service selector to conductor I8 so that it operates in parallel with the relays A4 and A5. By the closing of contact I25p2 the winding II of relay O2 is connected in parallel with relay C2; resistance I26, contact I25p2, wiper I21, contact I28 of the service selector DW2, winding II of relay O2, conductor 20.

The relay AB, when operated, prepares at the contact I29a6 the calling of the subscriber T112 of the two-conductor junction. It opens at the contacts I3Ia6 and I32a6, the circuit of the control relay V and the rotary magnet D3 of the discriminator ML, connects the relay H2 at the contact I3Ila6 and prepares at the contact I33a6 the circuits for the relays F and G. The contact I'34a6 is used for the operation of the meter of the calling subscriber, after termination of a revertive connection.

The relay N opens at the contact I95n the circuit of relay O2 (winding I) and at the contact IIIBn the access means to the start conductor I99. By opening contact I35n the short circuit is removed from winding II of relay N, and at the contact I36n a locking circuit controlled by contact. I3Ia4 is established over the winding II of relay N.

When the calling subscriber TnZ sends out a train of numerical impulses corresponding to the second digit of the marking number for an internal connection, the impulses are received by both relays A and A6. The setting of the numerical impulse receiver arranged subsequent to the group selector IGW is here without interest. The discriminator ML associated with the revertive transmitter RU2 is set: contacts I32a6, I38), I39g, I49h2, rotary magnet D3 of the discriminator, At the contact I3Ia6 the connection of relay V takes place and the relay short-circuits its winding II at the contact I4Iu, so that its armature is held attracted during the train of impulses. Contact I421) is opened, whereby any action on relays F and G by the wiper I43 of the discriminator lVlL during the setting thereof is prevented.

After the number has been selected the wiper I43 of the discriminator is set on contact I44. The relay V restores as contact I3Ia6 remains open. Contact I420 is closed and relay F operates. It looks up at contact I45 in a circuit dependent on contact M6712 and closes at the contact I4'If a circuit for the cut-off relay T3 which passes over the wiper I48, contact I49 of the service selector DW2 and contact H1602. Relay T3 operates and opens at the contacts I50t3, I5I't3 and I52t3 the conductors I8, I9, 20 of the access means to the group selector IGW. The relay A4 of this access means and the relays A5, B5 and C2 in the group selector are restored. The group selector and the subsequent similarly arranged numerical impulse receiver of the connection path set are released and may thereafter be engaged for completing a new connection, The seizure of group selector IGW is only possible by an access means 28, 29, 30, since the access means I8, I9, 29 for party line subscribers is locked at the preselector VW.

In addition to the switch operations described above the relay F has opened the contact I38 in the circuit of the operating magnet D3 of the discriminator and has established the ringing circuit at the contact I531: source of alternating current, winding I of relay Ra2, contact I54ra2, I53 I29a6, wiper I55 and contact I56 of the service selector DW2, conductor I9, contact and wiper of the preselector VW, contacts I4rI, 25tI', conductors la, laI, choke DrI, bell of the subscriber station TnI, winding I of relay EI, earth A small fraction of the ringing current flows over the condenser KI and the contact 3eI of the blocking circuit previous to the subscriber station TnI. The operation of the bell is thereby not influenced in any appreciable manner. The relay Ra2 does not energise in the ringing circuit.

When the called subscriber TnI answers, the relays EI and R112 operate, relay EI performing the above described switch-over actions. The relay Ra2 locks itself energised at the contact I5Ira2 in a locking circuit controlled by contact I58h2 and passing over its winding II. It disconnects its winding I by opening contact I54ra2, effecting a connection, over contact I59ra2 and the choke Dr6, to the feeding circuit of the subscriber TnI over conductor I9.

The subscribers T712 and TnI are now connected with each other. If, upon termination of the conversation, the calling subscriber T122 hangs up, relay A6 will be restored and return its contacts to their rest position. Since the relay H2 which is directly controlled by relay A6 is a slow relay the contacts I69h2 and I63ra2 remain in their operative position for a short period of time after the contact I34a6 has been closed. The resistance I26 is short-circuited whereby the current through conductor 20 is increased, so that the meter Z2 of the calling subscriber Tn2 which is connected over contact IIrI and the wiper 9 of the preselector to the conductor 20, can energise.

The relay V operates, because the contact I 3Ia6 is closed. When the contacts of the slow to release relay H2 restore, relay F is disconnected and restored. At the contact I60h2 the relay V is disconnected and at the contact I6Ih2 the circuit of the operating magnet D3 is prepared. When the relay V is restored, the following circuit is closed: contact [6221, off-normal contact I63lcml of the discriminator, contact I6Ih2, rotary magnet D3, The discriminator takes one step. At the same time the relay V is switched-in over contact I64d3, opening at the contact I621) the circuit of the rotary magnet, thus de-energising it. The relay V and the rotary magnet, D3 are alternately connected by their mutual interaction until the discriminator reaches its position of rest in which the off-normal contact I63lcml is open and the circuit of the rotary magnet D3 is finally interrupted.

When the relay H2 is restored, relay G is connected over contacts I68h2 and I6Ikm2 (olfnormal contact of discriminator). The circuit over relay P2 and the winding I of relay N is broken. At the contact I25p2 the locking circuit over the windings II of the relays O2 and TI is opened. As the contact I25t3 of the relay T3 which is disconnected at the contact I4'If by the release of relay F and which has a long delay when restoring, is still open for some time, the relay TI in the pre-selector VW can restore and. step the pre-selector round into its rest position.

A seizure of the revertive transmitter RU2 cannot take place during the release movement of the discriminator ML because the start conductor IE9 is connected to the start relay An2 only in the rest position of the discriminator (wiper III) on contact I I I). In all the operative positions of the discriminator the start conductor H19 is connected to the extension start-conductor I2I over the wiper I I I and one of the inter-connected contacts I65.

Testing on the service elector DWZ during the release movement of the discriminator ML is also prevented, because the relay G is energised and keeps the contact II!!! in the circuit of the testing relay P2 opened.

The marking number for internal connections can obviously also have more than two digits. In such an instance the revertive transmitter is associated with adiscriminator which releases the set connection selectors only after the current impulses corresponding to all the digits of the marking number have been sent out and which effects the calling of the second subscriber of the two-conductor junction.

2. The calling subscriber sends out an impulse train which does not correspond to the second digit of the marking number of internal connections release of the revertive transmitter RUZ -con-' nected to the access means I8, I91, 20 takes place.

The wiper I43 of the discriminator ML is set on one of the interconnected contacts In, by the second train of impulses. After the release of the relay V re-energised during this train of impulses relay G operates and locks itself energised at contact I'Hg, in a circuit dependent on contact I'IZhZ. It opens the circuit of relay P2 and the winding I of relay N at the contact I IIg. Relay N remains energised over its winding II, as this winding is included in a locking circuit controlled by contact I3'Ia4. Relay P2 is restored and disconnects relay A6 at the contact I22p2 and relay 02 at the contact I25p2. Both relays restore. Relay H2 is disconnected. The discriminator is stepped on to its rest position. During the release movement of the discriminator ML relay G remains energised.

I claim:

1. In a telephone system, a first switch, a second switch, party lines and individual lines, means for seizing said first switch over any of said lines to extend a call and for transmitting thereto a signal code, said first switch effective upon receipt of said code if same comprises any of one or more predetermined codes to extend the call in a direction dependent upon said received code, said direction being the same regardless of whether the calling line is a party line or an individual line, said first switch effective upon receipt of said code if same comprises a predetermined code different from all of said one or more codes and if the calling line is a party line to cause said second switch to seize the calling line, means in said second switch operated to signal the wanted subscriber, thereby to extend the desired call, and means operated to release said first switch to make same available for another call before said first call is terminated.

2. In a party line telephone system, a party line, an automatic switch, reverting call equipment, means controlled by a calling subscriber at any substation on said line to extend a connection over said line to said switch, means for then operating the switch over said connection either to further extend the connection or to cause said reverting call equipment to connect with the connection at a point intermediate said calling substation and said switch, and means in said equipment for transmitting a signal to another substation on said party line.

3. In a telephone system, a party line, an automatic switch, reverting call equipment, means controlled by a calling subscriber at any substation onsaid line to extend a connection from said line to said switch, means in said switch then operated variably over said connection and effective if operated in one way to cause the switch to further extend said connection, means controlled by said switch in response to the operation of said last means in another way to connect said reverting call equipment to the connection at a point intermediate the calling substation and said switch, and means in said equipment for transmitting a signal to another substation on said party line.

4. A telephone system as claimed in claim 3, wherein said last means is automatically operated to transmit said signal responsive to said equipment being connected to said connection.

5. In a telephone system, a two-party line terminating in an exchange, an automatic switch, ring-back equipment, means in the exchange operated responsive to the initiation of a call on said line to seize said switch, a ringing circuit prepared by said means upon said operation thereof, said prepared circuit extending from the exchange over one or the other side of said line depending upon which of the substations on said line is calling, means in said switch operated variably over said line by the calling subscriber and effective if operated in one way to cause said switch to extend a connection therefrom, means controlled by theswitch in response to the operation of said last means in another way to connect said ring-back equipment to said ringing circuit, and means in said equipment operated responsive to said equipment being connected to said ringing circuit for automatically impressing ringing current thereupon.

6. In a telephone system, a plurality of party lines, a plurality of automatic switches each accessible to all of said lines, reverting call equipment common to said switches and also common to said lines, means responsive to a call on any of said lines for completing a connection from the calling line to one of said switches, means in said switch then operated variably over the calling line and effective if operated in one way to cause the switch to further extend said connection, and means controlled by said switch in response to the operation of said last means in another way to connect said reverting call equipment to the connection extended to said switch from the calling line.

7. In a party line telephone system, a party line substation, an automatic switch, reverting call equipment, means controlled by a calling subscriber at said substation to extend a connection from that substation to said switch, means in said switch then operated variably over said connection by the calling subscriber and effective if operated in one way to cause the switch to further extend the connection, means controlled by said switch in response to the operation of said last means in another way to connect said reverting call equipment to the connection at a point intermediate the calling substation and said switch, and discriminating means in said reverting call equipment thereafter controlled over the connection by the calling subscriber and effective at times to cause said switch and the portion of said connection extended thereby to release.

8. In a party line telephone system, a party line substation, an automatic switch, reverting call equipment, means controlled by a calling subscriber at said substation to extend a connection from that substation to said switch, means in said switch then operated variably over said connection by the calling subscriber and effective if operated in one way to cause the switch to further extend the connection, means controlled by said switch in response to the operation of said last means in another way to connect said reverting call equipment to the connection at a point intermediate the calling substation and said switch, and discriminating means in said reverting call equipment thereafter controlled over the connection by the calling subscriber and efiective at times to cause said equipment to be disconnected. from the connection.

9. In a party line telephone system, a plurality of party lines, an automatic switch, reverting call equipment, means for seizing said switch over any calling one of said lines and for controlling the switch thereover either to extend a connection or to cause said reverting call equipment to connect with the calling line, means operated to release said switch if said equipment is caused to connect with said calling line, said equipment being maintained connected with said line independently of said switch, means in said equipment then operated to transmit a signal back over said calling line, and means for seizing said switch over another one of said lines to extend a callwhile said reverting call equipment is still connected with said first calling line.

10. In a telephone system, party lines and individual lines, an automatic switch, reverting call equipment, means for seizing said switch over any of said lines to extend a call and for transmitting thereto a signal code, said switch eflective upon receipt of said code if same comprises any of one or more predetermined codes to extend the call in a direction depending upon the received code, said direction being the same regardless of whether said calling line is an individual line or a party line, said switch effective upon receipt of said code if same comprises a predetermined code difierent from said one or more codes and if the calling line is a party line to cause said reverting call equipment to seize the calling line, means then operated to release said switch to make same available for another call before said first call is terminated, means for preventing said switch from being seized by another party line for a call before termination of said first call, and means for seizing said switch over an individual line for another call before termination of said first call.

11. In a telephone system, a two-party line terminating in an exchange, a source of signaling current, means at the exchange responsive to the initiation of a call on said line, said means operated variably dependent upon which of the substations on said line is calling and effective, upon said operation, to automatically prepare one or the other side of the line to be connected to said source depending upon which of the substations on said line is calling, and means operated at times by the calling subscriber after one or the other side of the line has been so prepared to cause the prepared side of the line to be connected to said source.

JOSEF KUCHLEY.

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