US2247254A - Automatic telephone system - Google Patents

Description

June 24, 1941. w. SCHWENN AUTOMATIC TELEPHONE- SYSTEM Filed Dec. 21, 1938 2 Sheets-Sheet 1 (N bi- INVENTOR. WILL! SCHWENN June 24, 1941. w. SCHWENN AUTOMATIC TELEPHONE SYSTEM 2 Sheets-Sheet 2 Filed Dec. Zl, 1938 WILL! SCHWENN W M ATTORNEY.

Patented June 24, 1941 2,247,254 AUTOMATIC TELEPHONE SYSTEM Willi Schwenn, Berlin-Charlottenburg, Germany,

assignor to Fides Gesellschaft fur die Verwaltung und Vcrwertung von gewerblichen Schutzrechten mit beschrankter Haftung, Berlin, Germany, a corporation of Germany Application December 21, 1938, Serial No. 246,988

In Germany December 24, 1937 12 Claims. (01. 179-23) The invention relates to automatic telephone installations in which a local, for example, a sub-exchange is supplied with current from the lighting mains in which on failure of the power supply, receives current over a junction line from the main exchange.

With known arrangements of this kind the case is simple as under undisturbed condition of the installation the dialled impulses do not.

main exchange on failure of the power supply is very much more difficult when dealing with installations in which both-way operation is effected and the dialling pulses are transmitted as inductive direct currents or alternating currents. In such installations on account of the necessity of good impulsing and speech transmission, contrary to the known arrangements, no current feeding source can be applied to the connecting line under normal circumstances. In order in such systems, to ensure the auxiliary feeding means to the sub-exchange from the main exchange there are, in accordance with the invention, at the ends of the connecting line supervisory means provided which on failure of the local current supply bring into operation. switching means at the sub-exchange and these effect the connection of a source of current in the main exchange HVSt to the junction lines.

The invention will best be understood by reference to the specification and the accompanying drawings, in which Fig. 1 is a schematic diagramil-lustrating a sub-exchange UVST, a main exchange -I-IVSt, interconnecting trunk line FL, and the associated switching apparatus in each exchange. Figs 2A and 2B show the detail circuits of the schematic diagram which are necessary for a complete understanding of the invention. Fig. 2A shows the equipment in the sub-exchange at one :end of the trunk line FL and Fig. 2B shows the equipment in the main exchange at the other end of the trunk line FL.

Fig. 1 is aschematicdiagramof the arrangement by which the sub-exchange UVSt is con.- nected through transformers Trl, TrZ inthe two-way trunk line FL to the main exchange.

scriber, Tl for example, on taking down his rer The subscriber cf the sub-exchange is fed with ceiver causes a callfinder AS to set itself on the calling line. By means of his calling dial the subscriber sends out impulses which position the line selector connected to the call finder on :to the terminals of the desired subscriber, say, T2.

Connections which pass from the sub-exchange over the line FL to the main exchange can be effected in two Ways. Either the subscriber, after a call finder has set itself on his line selects, by dialling a special digit, the line .selectorLW which is connected via repeater Uel to line L3. Further digits are then transmitted from the repeater Uel via the transformer TrLline .FL to the transformer Tr2, repeater Ue2, group selector GW3 of the main exchange. The direct current pulses from the calling subscriber become inductive direct current pulses in the repeater Uel. These impulses pass as such over the lineFL and in repeater Ue2 at the main exchange are transformed again into pure direct current pulses. There is the further possibility of asubscriber of the sub-exchange UVSt to effect connections to the main exchange via the call finder and line selector if, after taking down his receiver, he presses a key and thereby causes the operation of a mixing selector MW at the sub-exchange which sets itself on his line. When the selector MW has found the calling line, the call finder AS is released and returns to its home position. The dialling pulses from the calling subscriber Tl pass over the line TL, resting contact w, line Ll, mixing selector MW, repeater Uel, transformer Trl, resting contact v, line FL, resting contact 1/, transformer Tr2, contact a to the group select0rGW3.

Connections from the main to the sub-exchange pass from the group selector GWI over resting contact a of the change-over switching arrangement Ub, resting contact a of the re-' peater U62, transformer Tr2, resting contact y of the change-over switching arrangement Uh, line FL, resting contact 1;, transformer Trl, repeater Uel, mixing selector MW to the call finder AS. The call finder starts up and sets itself on the calling line La which is, similarly to a subscribers line, connected to the contact bank of the call finder. The direct current pulses from the group selector GWI of the main exchange are transformed into inductive direct current pulses in the repeater UeZ and are transmitted over the line FL to the repeater Uel of the sub-exchange. In the repeater Uel, the inductive pulses are transformedback into pure direct current pulses and pass as such to the line selector LW. The line selector is then set on the terminals of the called subscriber. Among the subscribers of the sub-exchange is one, TI according to the example given, privileged in so far as by failure of the power supply he is connected to the contacts to and c of the change-over switching arrangement so that line TL is immediately connected via line L2 to the line FL and switched through to the main exchange. At the main exchange on the failure of the power supply at the sub-exchange, contacts y and 11, of the switching arrangement Ub reverse. Subscriber Tl can set up outgoing calls which, at the main exchange, pass via the preselector VW and the group selector GWZ. He can also receive calls from the main exchange which pass via group selector GW I, the reversed contact a of Ub, the repeater Ue3, the home contact of the preselector VW, the reversed contact of U1), the line FL, reversed contact '0 of Ua, line L2, reversed contact to the subscribers line TL. If in the direction main to sub-exchange a call does not, as in Fig. 1 arrive over a group selector GWI, but comes via a line selector, then repeater Ue 3 in the main exchange can be dispensed with as calling current can be sent out from the line selector to the privileged subscriber.

In Figs. 2A and 2B the circuit details of the schematic are shown so far as these are necessary to an understanding of the invention.

The current feeding arrangements of the subexchange UVSt are effected in known manner through a rectifier connected to the alternating supply WQ. 7 I

Current from the supply'WQ through the rectifier is'fed" to the supervisory relays W and V over the circuit: 60 volts, windings of relays W and V, contact 'Ia', earth. So long as current is delivered from WQ, both relaysW and V are energized. Parallel to the relay W is a condenser Cp of large capacity so that relay-W requires a greater operating time than relay V. The purpose of this arrangement is explained later. When relays W and V are energized, the subscribers station TI is connected to the wires al/bl which correspond to the line L! of Fig. 1 via contacts 2'10 and 4w. The junction line FL is connectedto the transformer TTI at the subexchange, the upper wire of via contacts H12 and-l 13wv and the lower wire bf via contact 61). Repeater Uel is reached by the transformer Trl The setting up of connections under normal conditions is not pertinent to the invention and will therefore not be described.

If the current supplyat the sub-exchange fails, the supervisory relays W and V of the changeover switching arrangement Ua release. Station TI is now switched directly on to the line FL. As aresult of this operation at the sub-exchange the current feeding source at the main exchange is connected to the line FL. After the switching over the followingcircuit is formed for the relay S of the change-over group Ub at the main exchange earth, indicator SZ at station Ti, choke coil Dral, contact Ir, I31) of change-over group ca, wire of of line FL, upperhalf winding of transformer Tr2, contact 3071, winding I of relay S, contact 32y, winding II of relay S, battery, earth. Relay S of the change-over group Ub operates in this circuit and closes the following circuit for relay Y: earth, contact Ms, winding of the slowacting relay Y, battery, earth.

Relay-Y closes the following circuit for relay U: earth, contacts 36y, 35s, winding of relay U,

battery, earth. Relay Y at contact lBy inter-- rupts the connecting of line FL to transformer Tr2 while simultaneously at contact l9y the feeding bridge relay A is connected to the lower wire of the line FL. Relay S is connected to the upper wire line FL via contact Hu and, after relay Y has operated, the high resistance winding of relay S is disconnected by the opening of contact 32y. Relay S locks up over: earth, battery, Wi of low resistance, contact Ely, winding I of relay S, contact 39h, Ilu, wire a) of the line FL, contacts i311, 1x, choke coil Dral, indicator SZ, earth. At contact lliu the circuit for connecting line FL to the preselector VW is prepared. Relay U prepares further by closure of its contacts Mu, the busy circuit for incoming calls.

When the subscriber Ti of the sub-exchange takes down his receiver to efiect a connection the following circuit is closed; earth, winding of relay A in the main exchange, contact 193/, wire bf, contact 522, winding III of the relay X in the subexchange, contact 320, closed subscribers loop Tl, contact lw, windings I and II of relay X, contact I322, wire of, contacts Wu, 3071., winding I of relay S, contact My, resistance W2, battery, earth. 7

Relay X at the sub-exchange operates in this circuit and relay A at the main exchange. Relay X by means of its contacts 1x and 9x disconnects both choke coils Dral and DTaZ and at the same time the circuit of the indicator SZ and the earth potential. Further, relay X at its contact 8r short-circuits its own winding II so that it operates as a slow-to-release relay during the loop interruptions resulting from dialling.

In the change-over group Ub at the main exchange, relay A by means of its contact 2111 closes the following loop to the calling relay Row of the preselector VW: earth, battery, winding I of relay Row, contact 15 of the test relay of the selector, contact 28drb, winding II of relay Drb, contact 21a, contact if, winding II of relay Row, earth. The calling relay operates in this circuit and effects in known manner" the start of the preselector VW. As soon as the preselector has left its home position, relay E, previously energized by direct current, of the repeater Ue3, releases. This has the result that U63 can no longer be seized via group selector GWI in the incoming direction; Relay A further, at its contact 28a, switches through the wire a to the pre-selector VW. The opening of contact 2 la disconnects the calling relay R from the talking wires. When the preselector VW has found a free group selector, the test relay T operates.

Subscriber Tl receives in known manner dialling tone from the group selector seized by the preselector VW over the following circuit: a wire from the group selector, a wiper of the preselector VW, contacts t, 261;, 29a, talking condenser, contact l6u, wire of, contact I31), c, condenser C2, contact lw, subscriber station Tl, contact 3w, condenser C3, contact 50, wire bf, contact 19y, talking condenser, contact 24q, contacts t, b wiper of preselector, b wire of group selector.

If the subscriber now dials to set the group 7 and line selectors, his loop circuit is alternately opened and closed. Thereby relays A and S of the change-over group Ub are impulsively released. Relay A at its contact 21a interrupts the impulse loop to the group selector. At the first rel-ease of relay S a short-circuit for relay Q is opened at contact 358. Relay Q operates in series with relay U. Relay Q bridges, at its contact 25!; the relay Drb serving as bridging choke forthe duration of theimpulse groups. The talking wires to subscriber Tl are cut off :by opening of contacts 24d and 26q during the dialling period. At the end of this, relays A and S operate continuously again. Resulting from this relay Q releases. The talking wires to the calling su'bscriber are again switched through. Further, relay Drb again operates and at itscontact 28 drb interrupts the short-circuit on its highly inductive'winding I. Further processes for effecting the connection are not part of the inventionand are therefore not described. At the end of the conversation when subscriber Tl hangs up the receiver, relay X in the sub and relay A in the main exchange release which brings about the release of the preselector and the selector seized by it. Relay S at the main exchange is held energized over the earth potential and the indicator S2 at subscriber station Tl in the following circuit: earth, indicator SZ, choke coil Dml, contact 1r, I31), wire of, contacts flu, 30h, winding I of relay S, contact 3| resistance Wi, battery, earth. Relay S maintains relays Y and U energized. In this way the feeding battery in the main exchange remains connected to the line FL. If subscriber Tl of the sub-exchange is, after failure of the power supply, desired for a connection from the main exchange via the group selector GWI, relayA-3 in the calling repeater U63 operates via: earth, battery, wiper c of group selector GWI, contacts Mu, 50c, 5M3, 5303, 54112, 55q3, winding III of relay A3, earth. Relay A3 operates and breaks at its contact 5Ia3 the shortcircuit of the busy relayC3. C3 operates in series with A3 and breaks at the contact 5303 the original busy circuit. The circuit for winding III of relay A3 is thereby broken. Relay A3 locks up over both its windings connected to the talking wires and the loop to the group selector: earth, winding I of relay A3, contact 3910, wiper b of the group selector 'G-W'l, loop .at group selector, wiper a of GWI, contact 382;, winding II of relay A3, battery, earth. The occupancy circuit is held via: earth, resistance W13, contact 5203, winding of relay C3 contacts 50c, Mu, wiper c of GWI, battery, earth. Relay C3 feeds the following circuit for the relay Q3: earth contacts 1903, 1833,, 11113, 15122, 14:13, winding of slow relay Q3, resistance Wifi, battery, earth. Relay Q3 at its contact 55113 disconnects the high resistance winding II of relay E from .the direct current supply which flows via wiper c of the preselector in .its home position. Relay E is held energized via the low resistance winding I, in the following circuit: earth, contacts 1.903, 8803, '66q3, winding I of relay E, wiper c of the preselector VW in the home position, test relay T of the preselector, wiper d of VW in the home position, battery, earth. Further, relay Q3 switches through at its contacts 58q3 and 59q3, the talking wires from the group selectorv line wipers to thechangeover group Ub.

If the calling subscriber now dials, a repetition of the impulses and transmission of ringing current to subscriber TI is prevented in the following manner: By the loop interruptions in the group selector GW! resulting from dialling, relay A3 of the repeater Ue3 releases impulsively. On the first release of .relay A3 the short circuit of relay V! is broken by the opening of the contact "a3. Relay VI operates in series with relay Q3, it opens its contact Biol and thereby prevents the application of ringing current generator *RQ. Further, it closes the following circuit for relay V2: earth, contact Hui, winding II of relay V2, resistance Wid, battery, earth. During :impulse transmission relay V2 is impulsively short-circuited .at contact 10123 and locks up during the series of impulses. At the conclusionof the impulses relay A3 operates and remains operated; Relay V2 releases due to the continued closing of contact Illa-3, and completes the short circuit around relay VI via contacts 74:13 and 1502; relay Vl releases. Relay V2 becomes energized via its winding I and the 10 second switch over the following circuit: earth, 10 second switch, contacts 69113, 6803, 67.93, winding I of relay V2, battery, earth. Calling current is now sent to the call receiving relay R of the change-over group Ub over the following circuit: calling current generator RQ in repeater U63, contacts 6121i,

6202, winding II of relay Y3, contacts 58q3, 281 call receiving relay R, contacts 21a, 23q,24q, 5'9q3, 64s3, earth. Relay Y3 as a result of the shortcircuiting of its winding I at contact $3 is not operated by the calling current. 0n the contrary call responding relay R operates in the change-over group III). Via contact 331', relay H is energized. Relay 'H at contact 22h switches the upper talking wire through to the subscriber TI. After this wire has been switched through ringing current flows parallel to the ringing responding relay R to the subscriber Tl over the following circuit: ringing generator RQ in repeater Ue3, contacts Blvl, 62112, winding II "of relay Y3, contacts 58q3, 2 61], 22h, condenser "F511, wire a), contacts 132), winding II of relay 'X, condenser C2, contact lw, subscriber T-ls be'll, contacts 310, condenser C3, contact 51), wire bf, contact I9y, condenser, contacts 24g, 59q3, -64s3, earth. Relay H in the change-over group "Ub cuts off the relay S from the upper wire of the line FL at contact 30h during the calling period. Relay S during this time is held energized in the following circuit: earth, contact 29h, winding I of relay S, contact 3ly, resistance W2, battery, earth. During the non-ringing intervals relays A and S of Ub are energized. Relay A at its contact 21a closes the direct current loop-for relay Y3 of the repeater Ue3. RelayY3 operates and at its contact 691 3 interrupts the circuit for the call connecting relay V2. In this way the transmission of ringing current is stopped. By the energization of relay Y3, the short-circuit for relay S3 is broken at contact "U3. Relay S3 operates in series with relay Q3. The connection is now established. The release of the connection can be effected by the called subscriber T! by back release, or by the calling subscriber. "If the called subscriber Tl hangs up, relay A in the change-over group Ub releases. Release of relay A results in the release of relay Y3 in the repeater Ue3 whereby the release of the selectors is effected.

If the calling subscriber hangs up, the loop in the group selector GWI is broken and relay A3 in the rep-eater Ueil releases. Relay C3 is short circuited at contact 5M3. Relay C releases and by opening its contacts 1903 and 8003, opens the holding circuit of the relays Q3 and S3. Relay Q3 is slow to release and breaks the circuit to the selector GWI at the contact 5$q3 whereby the release of the selectors is effected.

The talking circuit to the called subscriber is broken at contacts 58q3, 59113 after relay Q3 has released.

If now the called subscriber Tl hangs :up, relay A of Ub releases. Relay *8 is, however, held energized until the power network at the subexchange is again effective.

If the power supply at the sub-exchange is restored during a conversation originating with subscriber Ti the energization of the supervisory relays W and V during a connection over the line FL and the relay X in the feeding bridge of the main exchange, is prevented. The latter relay at its contact Mr breaks the circuit for both relays. At, the end of the conversation the relay X releases. Relays W and V can now operate. In order to prevent permanent energization of both feeding bridge relays A and S in the changeover group Ub via the repeating winding of the transformer Tr'l of the sub-exchange, the two supervisory relays W and V have differing operating times. Relay V operates first opening its contacts 517 and I322 and closing to and Ho. Somewhat later contact lilw closes. The loop to the main exchange is thereby interrupted for a period of time so that relay S and the relays in the change-over group Ub' which are dependent on this can definitely release. If relay W is operated, the line FL is switched through to the transformer Trl of the sub-exchange. In the main exchange after release of relay S, relays Y and U release which results in again connecting the line FL to the transformer Tr2.

What is claimed is:

1. In an automatic telephone system, a subexchange having a local source of operating current, a, main exchange, a trunk line interconnecting said exchanges, a sub-exchange subscribers station, switching equipment in said sub-exchange controllable from said station for extending'cormections via said trunk line to said main exchange and controllable from said main exchangevia said trunk, line for extending connections to said station, means operated responsive to the failure of said local operating current for disconnecting said switching equipment and for connecting said station to said trunk line, and means in said main exchange operated responsive to said connection for feeding operating current over said trunk line to permit connections to be established between said station and said main exchange in either direction over said trunk line. 1 2. In an automatic telephone system, a main exchange, a sub-exchange, a trunk line interconnecting said exchanges, a source of operating current for each of said exchanges, a sub-exchange subscribens station, switching apparatus controllable from said station for extending connections to other local stations or via said trunk line to said main exchange, and changeover means operated responsive to the failure of sub-exchange operating current for disconnecting said apparatus and for connecting said station to said main exchange operating current via said trunk to thereby permit said station to extenddirect connections to said main exchange viasaid trunk line.

3. In an automatic telephone system, a main exchange, a sub-exchange, a trunk line interconnecting said exchanges, a source of operating current for each of said exchanges, a sub-exchange sulbscrib'ers station, switching apparatus controllable from said station for extending connections to other local stations or via said trunk line to said main exchange, change-over means operated responsive to the failure of sub-exchange operating current for disconnecting said apparatus and for connecting said station to said main exchange operating current via said trunk to thereby permit said station to extend direct connections to said main exchange via said trunk line, and means in said sub-exchange operated responsive to the establishment of a direct connection for preventing the reoperation of said change-over means togreconnect said switching apparatus. I

4. In an automatic telephone system, a main exchange, a trunk line interconnecting said exchanges; a source of operating current for each of said exchanges, a sub-exchange subscribers station, switching apparatus controllable fromrsaid station for extending connections to other local stations or via said trunk line to said main exchange, change-over means operated responsive to the failure of sub-exchange operating current for disconnecting said apparatus and for connecting said station to said main exchange op-' erating current via said trunk to thereby permit said station to extend direct connections to said main exchange via saidtrunk line, and means in said sub-exchange operated responsive to the establishment of a direct connection for'preventing the reoperation of said change-over means to reconnect said switching apparatus in. the event that the sub-exchange operating current is reestablished. a

5. In atelephone system, a sub-exchangaa main exchange, a trunkline interconnecting said exchanges, a local source-of operating current for said sub-exchange, a subscribers station, switching means in said sub-exchange operated responsive tofailure of said operating current for connecting said station to said trunk line, a source of operating current for said main exchange, and supervisory means in said main. exchange operated responsive to said connection for connecting said main exchange operating current to said station via said trunk line.

6. In a telephone system, a sub-exchange, a main exchange, a trunk line interconnecting said exchanges, a local source of operating current for said sub-exchange, a subscribers station, switching means in said subeexchange operated responsive to failure of said operating current for connecting said station to said trunk line, a source of operating current for said main exchange, supervisory means in said main exchange operated responsive to said connection for connecting said main exchange operating current to said station via said trunk line, said switching means in the sub-exchange controlled responsive to the reestablishment of the localsub-exchange operating current for disconnecting said station from said trunk line and for restoring the supervisory means in said main exchange to normal.

7. In a telephone system, a first exchange, a second exchange, a transformer, a trunk line interconnecting said exchanges and terminating in said transformer at said second exchange, a local source of operating current for said first exchange, a subscribers station, switching means in said first exchange operated responsive to the failure of said operating current for connecting said station to said trunk line and for placing a potential on one conductor of said trunk line, a local source of operating current for said second exchange, supervisory means connected to the mid-point of said transformer operated over the said one conductor of said trunk line for connecting said second exchange operating current to said station via said trunk line.

8. In a telephone system, a branch exchange, a main exchange, a transformer at said main exchange, a trunk line interconnecting said exchanges and terminating at one end in said transformer, a local source of operating current for said branch exchange, a subscriber's station,

} switching means in said branch exchange operated responsive to the failure of said operating current for connecting said station to said trunk line, supervisory means connected to the midpoint of said transformer operated responsive to the connection of said station to said trunk line, control means, auxiliary means operated responsive to the operation of said supervisory means for connecting said supervisory means to said trunk line independently of said transformer and for connecting said control means to said trunk line, and means operated responsive to the initiation of a call from said station for operating said control means to thereby permit the extension of a connection over said trunk line to a subscriber in said main office.

9. A system as claimed in claim 8 including a finder switch, the control means starting said finder switch to find an idle line extending to main exchange switching apparatus and repeating dialled impulses received from the said station to thereby control said switching apparatus to extend the connection to a main exchange subscriber.

10. In a telephone system, a main and a subexchange, a trunk line between said exchanges, subscribers lines terminating in said exchanges, automatic switchin equipmentin said exchanges, a local source of operating current for said subexchange, means for extending talking connections from subscribers in one exchange to subscribers in the other exchange through said switching equipment and over said trunk line, and means in said sub-exchange operated responsive to the failure of the operating current thereat for connecting a particular one of the sub-exchange subscribers to said trunk line independently of the switching equipment in the subexchange whereby talking connections between said particular subscriber and subscribers in the main exchange are established through the main exchange switching equipment and over the trunk line.

11. In a telephone system, a main and a subexchange, a trunk line between said exchanges, subscribers lines terminating in said exchanges, automatic switching equipmentin said exchanges, a local source of operating current for said sub-exchange, means for extending talking connections from subscribers in one exchange to subscribers in the other exchange through said switching equipment and over said trunk line, means in said sub-exchange operated responsive to the failure of the operating current thereat for connecting a particular one of the sub-exchange subscribers to said trunk line independently of the switching equipment in the sub-exchange whereby talking connections between said particular subscriber and subscribers in the main exchange are established through the main exchange switching equipment and over the trunk line, and means in the sub-exchange controlled over the trunk line during the time that said particular subscriber is using his telephone for preventing the means operated responsive to the failure of the sub-exchange operating current from disconnecting said subscriber from said trunk line in the event that the sub-exchange operating current is reestablished.

12. In a telephone system, a main and a subexchange, automatic switching equipment including a repeater in said exchanges, a trunk line between said exchanges terminating in the repeater at each of said exchanges, a subscriber's line terminating in said main exchange, a subscribers line terminating in said sub-exchange, a local source of operating current for said subexchange, means for extending connections between said subscribers through said switching equipment and repeaters and over said trunk line, and means responsive to the failure of the said operating current for extending connections between said subscribers independently of said repeaters.

WILLI SCHWENN.

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