US2167725A - Telephone system - Google Patents

Description

4 Sheets-Sheet 1 Aug. 1, 1939. w. PFAFF TELEFHONE SYSTEM Filed Feb. 17, 1937 Aug. 1, 1939. w. PFAFF 2,167,725

y TELEPHONE' SYSTEM ,f

Filed Feb. 17, 19:57 4 sheets-sheet 2 INVENTOK WALTER PFAFF ATTORNEY.

Aug. 1, 1939. w. PFAFF Y TELEPHONE SYSTEM Filed Feb. 17, 1957 4 Sheets-Sheet 5 ATTORNEY.

Aug. l, 1939. w. PFAFF TELEPHONE SYSTEM fi 4 Sheets-sheet 4 Filed Feb. 17, 1957 www@ Naw.

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INVENT OR. WALTER PFA FF ATTORNEY.

Patented Aug. l, 1939 TELEPHONE SYSTEM Walter Pfaff, Berlin-Zehlendorf, Germanrls- A signor to Siemens & Halske Aktiengesellschaft,

, Wernerwerk, Siemen many application February 17, 1931, semi N0. 126,163

In Germany March 6, 1936 Y l 1g claims. I'he invention relates to a circuit arrangement for call'indicating systems in association with.

telephone systems and aims at avoiding the withdrawal of the telephone system connecting path from the traffic when connection is established between the party who is sought and the call indicating system. 'I'his is achieved by the present invention in that the sought party causes a switch associated with the call indicating system to be set on-the line of the station from which he replies while simultaneously releasing the switches of the telephone system after a reply signal has been given.

The drawings comprising Figs. 1A, 1B, 2A and 2B show an embodiment of the invention. 'I'hey represent a private branch exchange system in association with a call indicating system. It may occur that a subscriber who is busy cannot answer a telephone call or that a visitor does not nd the desired person at his desk. In either case the seeking party can cause a special call indicating signal to be operated at various points in the works.` The desired party can then estalolsh connection to the calling party over the reply line after giving a special signal from the nearest equipment.

The individual switching operations are as follows:

When the seeking party at the station Tnl in Fig. lA takes up lthe receiver the call nder lil AS is set on the calling party in the known way. .citer the call finder has been set the testing re-A lay C energizes over wiper c of the call iinder AS and switches through the speaking leads at contacts ic and 2c. A feeding circuit is set up over relays AI and XI. The dileren'tial relay Xi does not energize. When the callingparty transmits a particular searching digit the iinal selector LW is set on a particular contact whereupon the following circuit is set up: positive, relay P, wiper c, lead 3 in Figs. 1A, 1B and 2A, winding I of relay Rl, contacts .4c2 and "tr, winding III of relay Tr and negative. In this circuit relays `l`P, RI and Tr energize. Relay Rl sets up the following circuit: positive, contacts 5c2, Srl and lu2, rotary magnet DSW and negative. 'I'he rotary magnet DSW advances the switch SW. Over the following circuit: positive, contact dsw, windingI of relay UI and negative, relay UI is energized. Relay UI at contact Sul completes a circuit for relay U2. Relay U2 opens contact lu2 and thereby breaks the circuit for the magnet DSW. At contact dsw the circuit for relay UI is opened and the latter releases and by opening contact Sul resstiult, near Berlin, Ger- (cl. 17e-1s) leases relay U2. 'I'he circuit over the rotary magnet DSW ls again setup over vcontact. 'lul so that the switch SW takes a further step forward. The rotary magnet DSW and the relays Ul and U2 operate together in the manner described un- 5 til the following circnit'becomes established over wiper d of the switch SW: positive. contact Ilvl, winding l1 of relay C2, contact Ilrl, wiper d of switch SW, lead l2 in Figs. 2A, 1B and 1A, wiper d of can finder as, Contact up, remy Hr, wiper :loV

d of the iinal selector LW, lead il, resistance WE and negative. In this circuit relay C2 in Fig. 2A energizes and opens contact 5c2 in the circuit for rotary magnet DSW. The switch SW is accordingly brought to rest. The guarding l5 circuit is prepared over contact i602.

The relay I-IT energizes over the circuit over wiper dof switch SW and releases the hnal selector LW in the known manner (not shown) and also ,releases the call nder AS. The known 20 guarding eilect over wiper c of call nder AS neutralized so that now the following i' circuit over wiper c of switch SW in Fig. 2A ca be set up: positive, contacts |662 and l'ltr, winding I of relay C2, wiper c of switch SW, lead il 25 in Figs. 2A, 1B and 1A, relay TI and negative.

The energizing of relay C! causes the line to be switched through at contactsV isc! and No2. Thus the following circuit is established for the calling party: negative, winding I or relay Si, winding I of relay X2, contact l9c2, wiper u of switch SW, lead 22 in Figs. 2A, lB and l, over the loop at station Tnl, lead 2l in Figs. lA, 1B and 2A, wiper l) of switch SW, Contact 201:2, winding II of relay X2, winding ll'. ci relay Si, and positive. Only relay Sl energiaes in the above circuit. Relay X2 is a. ldierental relay. Over contact 23sl relay VI is energized and breaks the short-circuit for winding I of relay C2 at contacts v2411i when contact 251| is closed after relay RI is released. The release of relays RI and Tr takes place when relay C2 energizes. Relay C2 opens contact c2 and closes contact 26c2. 'I'he following circuit is set up over relay V: positive, contact 3Ic2, winding III of relay V, wiper e of the switch DI in position 0, rotary magnet DMI, winding I of relay V and negative. In this circuit only relay V energizes; the rotary magnet DMI is not operated.

The calling party now dials the digit for con- 50 necting'up a particular calling signal.

It is assumed that the characterizing number for the desired party is the digit 6. In this case according to the embodiment the acoustic signal for the desired party consists of two short signals .5

followed by a long signal. Lamps LI and L3 are operated to constitute a visible signal.

'I'he impulse train of six impulses transmitted by the calling party is taken' up by relay SI in Fig. 2A yand in Fig. 2B is repeated by contact 2`|s| to the rotary magnet DMI of switch DI. 'I'he circuit of the rotary magnet DMI passes over positive, contacts 28D, 2312, 3011i, and 213|, rotary magnet DMI, winding I of` relay IV and negative. Relay V remains energized throughout the impulse train. When relay V falls back at the end of the train and the wipers of switch DI are in position 6 the following circuit is established over wiper a of switch DI: negative, contact 3211. wiper a of switch DI in position 6, lead 33, lamp LI and positive. Over wiper b of the switch DI the following circuit is established: negative, resistance W, contact 34D, wiper b, in position 8, lead 3l, lamp L3 and positive. Thus the lamps L| and L3 light up. Wiper c of switch DI is also set inr position 8 and is accordingly prepared for connecting up of an acoustic signal.

When relay V releases after the impulse train the following circuit is set up for rotary magnet DM2: positive, contacts 3611.2, 310|, 681'2 and 3811, rotary magnet DM2 and negative. The rotary magnet DM2 advances the wipers of switch D2 one step and by closing contact 33dm2 in Fig. 2A causes relay UI to be energized over positive, contact 39dm2, winding I of relay UI and negative. Relay U2 is energized over contact Sul. In Fig. 2B, over the windings II of relays UI and U2 and contacts 4312, 44s|, 451'2 and 461L2 a damping circuit is established soothat relays UI and U2 operate and release slowly and thus cause the switch D2 to be stepped slowly by the rotary magnet DM2. At contact 36u! relay U2 breaks a circuit for magnet DM2. Contact 39dm2 is opened and relay UI releases. At contact 3u| the circuit is broken for relay U2 so that the circuit for magnet DM2 is again established over contact 361L2. Magnet DM2 operates with relays UI and U2 as an interrupter so that the switch D2 is advanced until the called subscriber replies. When wiper c of switch D2 reaches contacts 8, 8, i0, and I2 the following circuit is established: positive, contact 40u, wiper c of switch DI in position 8, contacts 8, 8, I0, or I2, wiper c of switch D2 contact 48tr, and lead 4| over the bells at various positions in the works to negative. In rotating wiper c bridges adjacent contacts, so that ringing is not interrupted as the wiper passes over contacts l0, and I2, and the bells are thus rung in two short pulses followed by one long pulse. When the wanted party becomes aware of the signal which is individual to him he proceeds to the nearest telephone set. It will be assumed that he replies from the station Tn2 shown in Fig. 1A. When the receiver has been removed the call finder AS is set on the calling line. After the call finder has been setl the wanted party transmits a special relay digit whereby the final selector LW of the telephone system is set on a particular contact.

On account of this setting of the final selector LW the following circuit is set up over the test wiper c of the final selector LW: positive, test relay P, wiper c of the nal selector LW, lead 42 in Figs. 1A, 1B and 2A, relay R2, contacts 26c2, 41tr, winding III of relay Tr and negative.

Relay Tr opens contacts IItr and 41tr. Winding II of relay Tr was short-circuited so that relay Tr was made slow to operate. Shortly before relay Tr energizes relay R2 energizes. Conthe tact 481'2 closes so that the guarding circuit passes over winding I of relay C2 and contacts f2 and |8c2.y Relay R2 opens contact r2 and prevents further operation of the rotary magnet DM2. On

account of contact 4312 being opened the damping circuit for windings II of relays UI and U2 cannot be established when the switch MW is being set and consequently this switch is stepped rapidly. Relay'Tr also opens contact tr in Fig. 1A and closes contact Il tr so that a calling subscriber cannot start up a public exchange switch by dialling the characterizing digit for outgoing calls. Moreover, the switch MW in Fig. -2A is prevented from testing on a calling subscriber who has dialled the public exchange characterizing digit.

Relay R2 in Fig. 2A also closes contact 52r2 so that the rotary magnet DMW is energized over the following path: positive, contacts 53c3, 521'2, 54u2, rotary magnet DMW and negative. Magnet DMW closes contact SSdmw so that relay UI is energized. Relay UI closes the circuit for relay U2 over contact Sul. Relay U2 energizes and at contact 54112 breaks the circuit for the rotary magnet DMW. Magnet DMW restores contact 55dmw to normal. Relay UI releases so that contact 3u| is opened and thus a circuit for relay U2 is broken. Relay U2 again completes the circuit for magnet DMW over contact 54u2. Magnet DMW is operated together with relays UI and U2 until the following testing circuit is established: positive, contact 560| winding II of relay C3, contact 511'2, wiper d of switch MW, lead 58 in Figs. 2A, 1B and 1A, wiper d of call finder AS, contact |3p, relay HT wiper d of final selector LW, lead 53, resistance W2 and negative. In this circuit relay C3 in Fig. 2A energizes. By opening contact 53c3, relay C3 brings the switch MW to rest and at contact 6803 prepares the guarding circuit over wiper c of the switch MW. Relay HT energizes in the testing circuit over lead 58 and wiper.

d of the call finder AS and promotes the release of the final selector and of the call finder AS in the known way. On account of the release of the final selector the circuit over wiper c of this switch and lead 42 in Figs. 1A, 1B and 2A is broken. Relays R2 and Tr release. Relay Tr a lease of relay Tr the following guarding circuit is established over wiper c of switch MW: positive, contacts 60c3, Mtr and 6212i, winding I of relay C3, wiper c of switch MW, lead 63 in Figs. 2A, 1B and 1A, relay T2 and negative. The following feeding circuit is now established for the wanted party: negative, winding I of relay SI in Fig. 2A, winding I of relay X2, wiper a of switch MW, lead 64 in Figs. 2A, 1B and 1A over the loop at station Tn2, lead 65 in Figs. 1A, 1B and 2A, wiper b of switch MW, winding II of relay, X2 winding II of relay SI and positive.

I'he calling party at station T1l| and the wanted party who has replied from station T112 are now connected together over the switches SW and MW in Fig. 2A.

When the subscribers have conversed together and have both replaced their receivers the feeding bridge relay SI falls back. Relay SI breaks the circuit for relay V| at contact 233|. 'I'he rotary magnet DM2 is subjected to current over:

positive, contacts 38u! and 3lv|, wiper e of switch 7 position and the circuit for the rotary magnet DM2 over wiper e of switch D2 can no longer be set up. When the switch D2 is in the normal position switch DI is restored to normal in that the following circuit is set up for magnet DMI: positive, contacts 68c2, wiper d of switch D2 in the rest position. contact 50112, wiper e of switch DI in the working position, rotary magnet DMI,

winding I of relay V and negative. Magnet DMI closes contact |dml so that relay UI is energized over: positive, contacts IIvI and 10dmI, winding I of relayiU| and' negative. Relays-UI Y and U2 now :operate together with magnet rDMI until wiper e of switch DI has reached the normal: po-

sition. Whensthis .-has` occurredLthecircuitffor magnet DMI overwiper e is no longer established. l

Thus all thefdevices which-have been.. taken into use are onceinore in lthen'ormalposltion.

It is possible also for a subscriber connected to the exchange line AL to seize the devices of the call indicating system over the enquiry path if the party called in anenquiry call is absent from his position and accordingly does not reply.

An outgoing public exchange call is set up in the following way. After the receiver has been removed and the call finder AS has been set on the calling line the subscriber has to dial the digit characterizing outgoing public exchange calls. The following circuit is then set up over wiper c: positive, testing relay P, wiper c of the final selector LW, lead 12, contacts 50tr and 13b, winding I of relay R and negative. It should be noted that when there is a free public exchange line relay B is energized over: positive, contact 840| or 85s, contacts 86h, winding of relay B, contact 80h and negative, and its contacts assume the position shown inthe drawing. Relay R closes contacts 'I4r and '|5r. Contact 141' closes the circuitfor the rotary magnet DAW. The circuit Vpasses over positive, relay interrupter RU. contacts 16c| and 141, rotary magnet DAW and negative. The public exchange switch AW is stepped by the rotary magnet DAW until the following testing circuit is established: positive, contacts I'Iab abd Tir, winding II of relay CI, wiper d of the public exchange switch AW, lead I2, wiper d of call finder AS, contact |3p, relay HT. wiper d of the final selector LW, contacts 18h and |5ab, resistance WI and negative. In this circuit relay CI energizes and brings the switch to rest by opening contact 160|. Relay HT brings about the release 'of the final selector LW and of the call nder AS in the known man-l ner (not shown). 'I'he following guarding circuit is now established: positive, contacts 19u, 80122, and B|c| winding I of relay CI, wiper c of the public exchange switch AW lead I8, relay TI and negative. Relay CI switches through at contacts 82c| and 830|. T'he feed bridge relay S is energized and opens contact 85s. The circuit for relay B is broken by the opening of contact 85s. Relay B opens contact 86h and closes contact 81h. At the same time contact 13b has opened and contact 89h closed. Relay R falls back and a further impulse for setting a public exchange switch is transmitted over contact 89h 'to a. second public exchange switch.

Relay S switches through at contact 90s. The calling subscribed is thus connected with the public exchange line AL.

An incoming public exchange call is established in the following way.- Relay A is energized by the ringing current flowing over the exchange line. Relay A establishes a circuit for relay H over: positive, contact SI1', winding I of relay H,

contacts 92a and 92h and negative. locks up over contact 84c| or 05s, contact 94123, winding II of relay H, contact h and negative. Relay H establishes the following circuit: positive, contact 96h, windings II and I of relay C|,` wiper c of the public exchange switch AW in the normal position, lead 91, lead I8, relay TI and negative. Switching through is effected at contacts 82c| and 83c| by relay CI, while winding II of relay. CI is short-circuited by contact 8|c| and thus the line of subscriber TnI -is guarded in the known way. The following ringing circuit is set upzfffrom thevsour'ce RQ of ringingcurrent over contact 08h, winding I of relay S, winding IV of relay X, 'winding I of repeater Ue', contact 82cI, wiper a of the public exchange switch AW, lead 99, lead 22, to bell at station TnI, lead Relay H 2|, lead |00, wiper b of the exchange switch AW in the normal position, contact 83cI, winding 1I of repeater Ue, winding II of relay X, winding II of relay S and positive.

When the subscriber at station Tnl takes up the receiver relay S energizes. Relay S breaks the locking circuit for relay H and the circuit for relay B at contact 85s. Relay B releases and at contact 93h breaks the circuit for winding I of relay H. Relay H restores its contacts to normal. Current is fed to the called subscriber over contact IOIh.

After the switching through at contact 90s the calling public exchange subscriber is connected to the subscriber at Tnl. If now the exchange call is to be extended to another subscriber the subscriber at station 'I'nl promotes the establishment of an enquiry call. As a result of the transitory depression of key Tal the differential relay X disposed in the feeding circuit is energized and establishes the following circuit; positive, contacts |02c| and |0332, winding I of relay Z, contact |0411, resistance W4 and negative. Relay Z energizes and closes contact |052. When the key is released relay X falls back and contact I 03a: is opened. The following circuit is established: positive, contact I02cI, winding Il of relay Y, contact l05z, winding II of relay Z, winding I of relay Z, contact |0411, resistance W4 and negative. In this circuit relay Y is also energized and opens contact |04y and closes contact I 25g.

y The following circuit now obtains for relays Y and Z: positive, contact |02c|;,winding II of relay Y, contact |05z, winding II of relay Z, contact |2511, winding I of relay Y and negative. Relay Y establishes a holding bridge across the leads of the public exchange line over contact |053/ and resistance W5. Relay Y by opening contacts |06y and I0'Iy and closing contacts |081/ and |09@ causes the public exchange line AL to be switched over on to the enquiry line I|0/||I. 'I'he call finder AS is caused to be set on the enquiry line ||0/ by the loop over contacts |083/ and 90s, windings IV and III of the repeater Ue and contact |09y. After the call finder AS has been set impulses are transmitted for setting the final selector LW. The impulses are received by relay S and are repeated over the enquiry line ||0/||| by Contact 90s to relay A| in the final selector LW. If the final selector is set on the line of a subscriber who does not reply the enquiring party switches back on to the public exchange line. This is effected by again transitorily depressing the key. The diiferential relay X in the feeding circuit of subscriber Tn| is energized and short-circuits Winding II of relay Y and Z at contact |0332. Relay Z accordingly releases and opens contact |052. When a subscriber releases the key Tal relay X releases and contact |031: opens again. Relay -Y releases and switches back from the enquiry line on to the exchange line by opening contacts Illu and Illy and closing contacts Iliy and Illy. f

'Ihe subscriber at the calling station again causes the public exchange line to be switched over to the enquiry line in the manner already described. After this has been eiiected the characteristic digit for the call indicating device has to be dialled. The circuit for relays RI and Tr is set up over wiper e of the ilnal selector LW and lead 3 in Figs. 1A, 1B and 2A. Relay RI causes the switch SW to be set in the manner already described. The switch SW is brought to rest when the following circuit is established: positive, contact lllvl, winding II of relay C2, contact lirl, wiper d of switch SW, lead |12 in Figs. 2A, 1B and 1A, wiper d of the call ilnder AS, Contact |312, relay HT, wiper d of the final selector LW. lead I4, resistance W6 and negative. The switch SW is thus set on the enquiry line ||0/||I. Relay CI eiects the switching operations already described such as guarding and switching through while relay HT releases the nal selector LW and the call iinder'AS which has been set on the enquiry line. The subscriber at station Tnl now transmits the digits for operating the call indieating signal. The impulse trains transmitted are received by relay S and are repeated by contact s to relay SI in Fig. 2A. 'I'he setting .of the devices (switches D| and D2) for operating the call indicating signal takes place in the manner described.

When the wanted party perceives the signal he proceeds to the nearest telephone equipment and as already described causes the switch MW in Fig. 2A to be set on the line to the station from which he has replied by transmitting a characterizing digit. After this setting has been effected the following connection is established: from station Tnl over the public exchange switch AW, enquiry line lill/I Il in Figs. 1A, 1B and 2A, over the switches SW and MW in Fig. 2A and line- 64/65 in Figs. 2A, 1B and 1A to the station T112 from which the wanted party has replied.

It is possible for the subscriber who has replied from station Tn2 to take over the exchange call. For this purpose he has to operate the key Ta2. This energizes the differential relay X2 in Fig. 2A which is disposed in the feeding circuit. 'Ihe relay X2 opens contact H312 and closes contact ll42. The following circuit is established for relay RI: positive, contacts |5c|, H412, winding II of relay RI and negative. Relay RI closes contact Il Gal. When the subscriber releases the key relay X2 falls back. Contact ||4x2 opens and contact H312 closes. Relay RI on account of its slow operating features holds contact ||6r closed for a moment so that the following circuit obtains: positive, contacts ||5c|, H332, ||6r|, wiper e of switch SW, lead in Figs. 2A, 1B and 1A, contact H82, winding I of relay U and negative. Relay U is energized transitorily in the last mentioned circuit. Relay U opens contact 19u and closes contact IISu. Relay CI releases. Relay AB energizes. The release of relay Cl establishes the following locking circuit for delay U: positive, contacts ci and I'Ib winding II of relay U, contact |2011. and negative. Relay U maintains the feeding bridge. relay S energized over contact |2|u so that this relay is not deenergzed by the opening oi contacts 82c| and 83cl. The release of relay Cl breaks the circuit for relays Y and Z at contact I||2c|. Relays Y and Z restore their contacts to normal. The opening of contacts Illy and Illu and the closing of contacts |001 and lllly promotes the switching over from the enquiry line Ill/I on to the public exchange line AL. Through the energizing oi' relay U relay R is operated over: positive, contacts el and IIb, windings 11 and III of relay R, contact |2lu and negative. Relay R closes contact |2|r so that its winding II is short-circuited and it is accordingly rendered slow-to-release. It also closes contact '|41'. 'I'he public exchange switch AW is advanced by the rotary magnet DAW. The stepping continues until the following circuit is established: positive, contact |2'Ib, contact lir, winding In of relay Ci, wiper d, of .the public exchange switch AW, lead Il in Figs. 1A, 1B and 2A, wiper d of switch MW, contacts I22r2 and |23c3, winding I of relay Tr, contact I2lr| and |2512, wiper d of switch SW, lead ||2 in Figs, 2A, 1B and 1A, contacts |261' and |21ab, resistance Wl and negative. By opening contact 16c| relay CI brings the public exchange switch AW to rest. The exchange switch is thus set on the speaking leads 64 and 85 associated with station Tn2. 'I'hus the subscriber who has replied from station Tn! is connected to the public exchange line over the switch AW.

In the testing circuit for setting the public exchange switch AW on the line associated with station Tn2 relay Tr in Fig. 2A is also energid. At contact iltr breaks the circuit over wiper c of switch SW. Relay C2 releases. It breaks the circuit for relay SI at contacts |9c2 and 20c2.

Relay Sl releases and causes relay VI to release l by opening contact 233|. VRelays C2, SI and VI in their deenergized condition restore to normal the devices of the-call indicating system which have been used in the manner already described.

As may be seen from the preceding description a subscriber who has been sought over the en- Vquiry devices of the telephone system can cause a switch MW associated with the call indicating system to be set on the line of the station from which he replies by dialling a characteristic tending thereto, special control lines, and means for extending connections from calling or answering telephone lines to any one of said lines, a code calling system including first and second line ilnders, said finders having access to said telephone lines, signalling means located at points common to said stations, means operated when a connection is extended under control of a calling line to one of the special control lines for causing said first line finder to seize the calling line and extend a connection from said calling line to said second line ilnder, means for causing the extended connection to be released responsive to said seizure, means controlled by the calling line through said first line finder for operating said means in accordance with a predetermined code to signal a particular party, means operated when a connection is extended under control of an answering line to another one o f said special control lines for causing 1I *l said second line finder to seize the answering line,

'and means for causing said last extended connec tion to be released responsive to said last seizure.

. v2. In a signalling system, connector switches, a' plurality of lines having access to 'said switches, special positions` for said connector switches,

, means responsive to a call over any one of said said lines, means responsive to said operation of the connector for causing said line finder to seize said one line, and means responsive to said last seizure for causing the operated connector switch to be released.

3. In a system as claimed in claim 2, means responsive to a call over any other of said lines for seizing one of said connectors, means responsive to impulses over said other line for operating said last connector to another one of said special positions, a second line finder having access to said line and associated with the said first linefinder, means responsive to said operation of said last connector for causing the second line finder to seize said other line, and means responsive to said last seizure for causing said last operated connector switch to be released, whereby said oneline and said other line-are associated via said first line finder and said secondA line finder.

,4. In an automatic telephone system comprising a series of switches including a connector switch, a pluralitvof lines having access to said connector switch, a special position for said connector switch, a line finder havingV access to said lines, a trunk line terminating in said line finder, means responsive to a call over any of said lines for seizing one of said connectors, means responsive to impulses over said onefline for operating the connector to said special position, means responsive to the operation of the connector to said special position for causing said line finder to seize said one line and means responsive to said last seizure for causing said connector switch to be released.

5. In an automatic telephone system, a plurality of stations associated with a code calling system, signalling means common to said stations, means for extending a connection from a calling one of said stations to another station or to said signalling means, a trunk line, means for causing an incoming call over said trunk to be extended directly to a particular station, means controlled from Vsaid particular station for holding the trunk and for operating said signalling means to signal a particular called party, means lwhereby the called party may answer the signal from any one of said stations through the second-named means, and means controlled from the answering station for causing said last station to be connected with the trunk call independent of the second-named means. o

6. In a telephone system, subscribers substations and lines therefor, junction equipment having access to said lines, switching apparatus having access to said junction equipment, means at a plurality of stations controlled by subscribers thereat for seizing certain of said switching apparatus and for controlling said certain apparatus to cause said junction equipment to seize the lines of those stations, and means responsive to the seizure of each line for causing the certain apparatus seized and controlled thereover to be released, said junction equipment being thus associated with said plurality of stations concurrently and effective to join in a connection the lines thereof.

7. In a telephone system, subscribers' stations and lines therefor, a link circuit including a plurality of line finder switches each having access to' said lines, a plurality of seizing paths for said link, other links having access both to said lines and also to said first link, means responsive to a call over any of said lines for causing one of said other links to be associated with the calling line, and means for controlling said one link to seize said rst link over one of said paths, one of the line finders effective responsive to saidseizure to seize the calling line and to cause said one link to be disassociated therefrom, and means at another calling station for controlling one of said other links to seize said first link over another path, whereupon said first link is eifective to seize the line of the other calling station, to cause said last-mentioned one link to be released, and to join the calling subscribers in a connection.

8. In a telephone system, subscribers stations v'and lines therefor, switching equipment for extending calls of a particular character, other switching equipment for extending calls of a. different character, means responsive to a call over any of said lines for associating said rst switching equipment withv the calling line, and means at the. calling station for thereafter controlling said first switching equipment either to extend a call of'said particular character or to seize said other switching equipment, said other switchingA equipment effective if so seized to associate itself with the calling line and thereby cause said rst switching equipment tobe released.

9, In a telephone system, subscribers stations and lines therefor, switching equipment for extending a particular class of calls, switching equipment for extending each of a plurality of other classes of calls, means responsive to a calling condition on any of the lines for causing said first switching equipment to be associated with the calling line, and means at the calling station for thereafter controlling said first switching equipment either to extend a call of said particular class'or to seize the proper switching equipment for extending another class of call, the other switching equipment eifectiveif so seized to associate itself withthe calling line and thereby cause said first switching equipment to be released.

10. In a telephone system, subscribers stations and lines therefor, switching equipment for extending calls between said lines, a signalling means and other switching equipment associated therewith, means responsive to a calling condition on any of said lines for associating certain of said first switching equipment with the calling line, means at the calling station for thereafter controlling said certain switching equipment either to extend a call to another station or to seize said other switching equipment, said other switching equipment effective if so seized to associate itself with the calling line and to thereby cause certain switching equipment to be released,

Asaid other switching equipment then controllable by the subscriber at the calling station to actuate said signalling means, means for placing a calling condition on the line of any other station to respond to the signal and, when certain of said first switching equipment is associated with the responding line, for controlling said certain equipment to cause said other equipment to associate itself with the responding line, whereupon said certain equipment is released and said other switching equipment is effective to complete a connection between the calling and responding lines.

11. In a telephone system, subscribers stations and lines therefor, an inquiry line, switching equipment having access to said lines and eifective to respond to a calling condition upon any of the lines. a signalling means and other switching equipment associated therewith, a trunk line, means for connecting a subscribers line to said trunk line, said last means controllable by the subscriber to cause said trunk line to be held and to associate the subsribers line with the inquiry line to establish a calling condition thereon for the initiation of a call to another subscriber, means responsive to the calling condition on the inquiry line for associating certain of said rst switching equipment with the inquiry line, means at the calling station for thereafter controlling said certain switching equipment either to extend a call to another station or to seize said other switching equipment, said other switching equipment effective if so seized to associate itself with the inquiry line and thereby cause said certain switching equipment to be released, said other switching equipment then controllable by the subscriber at the said calling station to actuate said signalling means, means for placing a calling condition on the line of any other station to respond to the signal and, when certain of said first switching equipment is associated with the responding line. for controlling said certain equipment to cause said other switching equipment to associate itself with the responding line, whereupon said certain equipment is released and said other switching equipment is effective to associate the inquiry line and the responding line. thus completing a connection between the calling and the desired subscribers.

12. In a telephone system, subscribers stations and lines therefor, an inquiry line, a trunk line, a switch terminating said trunk line and having access over its wipers to said subscribers lines, means including said switch for completing a connection between one of the subscribers lines and the trunk line, means at the subscribers stanon for controlling said switch to hom seid trunk line and to seize said inquiry line, thereby to initiate an inquiry connection including said subscribers line, said wipers and said inquiry line, switching means accessible to said inquiry line for completing the inquiry connection between said one subscribers line and another of said subscribers lines, and means at the other subscribers station for causing said wipers to be moved from said one subscribers line to said other subscribers line and for causing said inquiry line and said switching means accessible thereto to be released, whereby said trunk connection is transferred to said other subscribers line and said one subscribers line is released.

WALTER PFAFF.

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