US2423084A - Telecommunication system employing voice frequency current for selective signaling - Google Patents

Telecommunication system employing voice frequency current for selective signaling Download PDF

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Publication number
US2423084A
US2423084A US486274A US48627443A US2423084A US 2423084 A US2423084 A US 2423084A US 486274 A US486274 A US 486274A US 48627443 A US48627443 A US 48627443A US 2423084 A US2423084 A US 2423084A
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United States
Prior art keywords
relay
signal
circuit
over
voice frequency
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Expired - Lifetime
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US486274A
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English (en)
Inventor
Hertog Martinus Den
Esmond P G Wright
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International Standard Electric Corp
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International Standard Electric Corp
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q1/00—Details of selecting apparatus or arrangements
    • H04Q1/18—Electrical details
    • H04Q1/30—Signalling arrangements; Manipulation of signalling currents
    • H04Q1/44—Signalling arrangements; Manipulation of signalling currents using alternate current
    • H04Q1/444—Signalling arrangements; Manipulation of signalling currents using alternate current with voice-band signalling frequencies
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q3/00—Selecting arrangements
    • H04Q3/0016—Arrangements providing connection between exchanges

Definitions

  • the present invention relates to alternating current communication systems, (e. g. telephone systems) employing voice frequency current for selective signaling (which will be referred to herein as dialing) and supervisory signaling.
  • alternating current communication systems e. g. telephone systems
  • voice frequency current for selective signaling (which will be referred to herein as dialing) and supervisory signaling.
  • An object of the invention is to provide means for switching the forward alternating current signalingcircuit over from the dialing condition to the communication condition.
  • the forward circuit is switched over from the dialing condition to the communication condition in response to a voice frequency signal transmitted back from a subsequent stage in the connection.
  • Fig. 1 is a schematic diagram showing the layout of part of an alternating current communication system (e. g. telephone system) in which connections are set up over machine switching apparatus.
  • alternating current communication system e. g. telephone system
  • Figs. 2 and 2a in conjunction constitute a circuit diagram of apparatus employed at the incoming end of a toll line.
  • Fig. 1 shows diagrammatically a known layout of a telecommunication (e. g. telephone) exchange network employing the Rotary system of automatic switching.
  • This network comprises three exchanges X, Y and Z.
  • Exchanges X and Y are connected by toll lines TLI terminated at their ends in toll line circuits TCI and T02 whilst exchanges Y and Z are connectedby toll lines 'ILlterminated at their ends in toll line circuits T03 and T04.
  • the apparatus in exchange X includes a finder Fl linked to a group selector GSI over a connecting circuit CCI which is associated with a register RGI over non-numerical switches SI. Similar apparatus is provided in exchanges Y and Z, the general operation of these registers and switches being well-known.
  • the register RGI then transmits the second routing digit which is received by the incoming toll line circuit TC2.
  • the circuit TC2 upon recognizing that the call is to terminate at the exchange Y, causes the register RG2 to be connected up over the switches F2, S2.
  • the register RG2 sends back to the register RG! 2. proceed to dial signal whereupon the register RGI transmits all the numerical stored digits to the register RG2.
  • the register RGI responds to this signal and thereupon releases itself and causes the speech circuit at the exchange to be. switched through.
  • the register RG2 then proceeds to control the setting of the group selectors G82, G83 and the final selector F8! to connect up the line leading to the substation B.
  • an answer signal is sent from exchange Y to exchange X to effect a metering or like operation.
  • the second routing digit is difierent and causes the circuit T02 to start up a finder F3 in place of the finder F2 so as tocause the circuit TCZ to be connected over the finder F3 and the outgoing .tollline circuitv T03 to anidle toll line TLZ terminating in an incoming toll line circuit T0 at exchangeZ.
  • the circuit T04 then sends.
  • the circuit T04 upon recognizing that the call is to terminate atthe exchange Z causes the register RG3 to be connected up over the switches F4, S3.
  • the register TG3 sends back a proceed to dial signal which is repeated at the tandem exchangesY. and.received by theregister. RGI.
  • the register RGl fthereupon transmits all the: numerical stored digits to the register RG3.
  • the register RGI respondsto th'i-ssignal and thereupon releases itself and-"causes the? speech circuit at the exchange X to be switched through.
  • the finder F5 is set in-rmoti'oniirrnplace' of the finder F4 and the call is routed? over the outgoing toll line circuit T05.
  • the register RGI-hasbcenabldto recognize by its own conditionwhether'the-signal represents a proceed to dial signal or'the end of selection signal; and the, answer signal is not received'bythe registerRGl but by the connecting circuit CC I It is necessary toensurethat the end of selection""signal is received by the register RGI withir'i'a' predetermined fixed'period of time from the transmissiOnofthe last digit, because otherwise there may.
  • one method of voicefrequency signalingnow in' use utilizes currents of two voice frequencies (er-g; 600 cycles and 750 cycle's) connected 'to the line simultaneously'for'use'as a prefik signal whichwill' prepare thereceiver for'the' reception of 'a short impulse-of 'asingle frequency:
  • These prefixed signals are particularly necessary after speech has" commenced “with'th'e consequent li'kelihood of interfering voice'frequency"currents:
  • Before-'tlie* speech period single frequencies-may'b'eused" without dangerfandit is proposed in'accordance with"the-presentinventionthat the proceed' to" dial signals shall each be transmitted *over' the tolllines TIi'l, T132, as'an' impulse'ofa single'frequency-"(e g: 750 cycles);
  • the switching arrangements may be such that certain selections to operators or special service positions are carried out by the transmission of only one numerical selection and, in consequence, the circuit ICE is powerless to make the necessary discrimination. It may be possible to avoid this difiiculty by modifying the switching layout to ensure that there are at least two numerical selections for every type of connection.
  • voice frequency impulses received over the toll line TLI are repeated over the outgoing speaking leads as direct current impulses.
  • a relay A is shown to respond to the voice frequency impulses received over TLI, but it should be understood that these impulses are preferably received by a thermionic valve circuit, a relay similar to the relay A being operated from the output of the valve circuit.
  • relay A When the line TLI is taken into use, relay A is operated by a pulse of current over the line and causes the obvious operation of the relay B which locks up over contact bl until the connection is released.
  • the contact 126 closes the forward loop circuit and the relay G operates when this loop circuit is complete, closing at Gl a circuit for the relay D over contacts 122, i2 and gl.
  • the contact dl closes the obvious circuit for the relay E which looks over contact e I.
  • the first series of forward impulses transmitted over the line TLI causes corresponding intermittent operation of the relay A, and the contact a2 repeats the impulses over the outgoing D. C. circuit, the short circuit at ca having been removed.
  • Relay A also causes the operation of the relay C through front contacts a4 and the back contacts lid.
  • the operation of the relay C closes the obvious circuit for relay H, which looks.
  • Relay C has, however, provided a locking circuit for itself at contact 02 and, being slow to release, remains operated throughout the digit. Subsequently relay B releases, but relay H remains operated, being held through contacts d4 and I25.
  • a proceed to dia signal consisting of a momentary opening of the backward loop causes the momentary release of the relay G.
  • Relay G opens the circuit of relay D which releases and at contacts d2, d3 connects a voice frequency (750 cycles) impulse .to the line TLI.
  • the release of relay D also causes the release of relay H.
  • relay G re-operates and relay D also re-operates.
  • the next train of impulses causes the re-operation of the relays C and H and the subsequent release of C at the end of the train.
  • the circuit TCZ recognizes that routing selection has been completed and that the next backward signal will be the end of selection signal.
  • the first impulse of the second of these trains will close a circuit through contacts a4, 02 and k3 for relay J which is provided with a locking contact it.
  • relay G releases D which immediately connects a 750 cycle impulse back over the line TLI.
  • Figs. 2 and 2b in combination show an alternative arrangement for use when it is found impossible to obtain a minimum of two numerical selections.
  • This alternative arrangement contemplates a modification to the terminating register RG3 so that it will transmit two backward impulses for the "end of selection signal the second following the first with a relatively small delay. If such impulses are suitably spaced, they will pass through all the D. C. and 50-cycle links in a built-up connection because they may be considered as two closely spaced proceed to dia signals.
  • relay G on seizure causes the operation of relays D and E as already explained.
  • the receipt of a proceed to dia signal causes the momentary release of relay G, and the conse quent operation of relay C over contacts 92 and e5 and the release of relay D which transmits a voice frequency impulse (750 cycles) over the line TL.
  • relay G closes a circuit for the relay H over contacts g2, cl and f5.
  • Relay C is slow to release and relay H is maintained operated for the release period of relay C.
  • the first interruption causes a voice frequency impulse (750 cycles) to be transmitted as just described.
  • the second interruption causes relay G to release a second time before relay H is restored; relay J operates and looks.
  • the operation of the relay J causes the release of relay H, and the connection of a second frequency (600 cycles) to the line TLI, as already described.
  • Relay H at contact n3 opens the circuit of the relay C which, on release, opens the circuit of relay J; the slowrelease time of relay J controlling the duration of the impulse of current of the two frequencies simultaneously.
  • the release of relay J the
  • relay D re-operates in preparation for the trans- 7 case: of. the first proceed to dial signal. subsequent proceed to-dial signal is sent back from-the registeriRGeand causes the circuit T64 to-operate'in:asimilar manner to the circuit 'lCZ and transmit backover the line TLziavoice frequenc impulse whicnpasses through the circuitsat'thewexchange Y and over the'line 'I'Ll to exchange X.
  • the endof selection signal from the: register RG3 is converted into a voice frequency-signal in the circuit T64 and transmitted back to-exchange X-in thisform as will be-readily understood from the preceding description.
  • a currentsource means for sending from said source voice frequency selective and supervisory signals from one: exchange to another for controlling the building up of the connection, including supervisory' signal consistingof asingle-direct current impulse and another kind consisting of a double direct: current impulse, means at one selector stage responsive to a voice frequency signal, and means forv transmitting back-the last-mentioned signal from a subsequent selector stage in the connection for establishing the communication over the connection.
  • In an alternating current communication systems plurality of exchanges, a plurality of linesterminating at said exchanges, means including; trunk lines and a series of stages of selectors at said exchanges for first selecting trunks and selectors to build up a. connection between a calling line at one exchange and a called ilinehat a secondexchange and then establish communication over said connection, acurrentsQurce, means for sending fromsaid source voice frequency selective and supervisory signals from .one. exchange to'another for controlling the building upotthaconnection, means responsive tooneikind of. supervisory signalto transmit back af single voice frequency and to another kind.
  • supervisory signal to transmit back two voice frequencieameans-at one selector stage responsive to a voice frequency signal .and means for transmitting back thevlast mentioned signal from.
  • a plurality of exchanges a plurality of lines terminating at said exchanges, meansi'neluding, trunk lines and a series of stages of selectors atsaid exchanges for first selecting trunks and selectors to build up a connection between a calling line at one exchange and a called line at a secondexchange and then establish communication over said connection
  • acurrent source means for sending from said source voice frequency selective and supervisory signals from one exchange to another for controlling the building up of the connection, means responsive to onekind of supervisory signalto transmit back a single voice frequency and to another kind of supervisory signal to transmit back two voice frequencies, means for changing. the voice frequency signal transmitted back upon the receipt at said subsequent stage of two successive. trains of selectivesignals withoutan intervening supervisory signal, means at one selector stage responsive to a voice frequency signal and means for transmitting back the lastv mentioned signal from a subsequentv selector stage in the connection for establishing the communication over the connection.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Interface Circuits In Exchanges (AREA)
US486274A 1940-06-11 1943-05-08 Telecommunication system employing voice frequency current for selective signaling Expired - Lifetime US2423084A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB289545X 1940-06-11

Publications (1)

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US2423084A true US2423084A (en) 1947-07-01

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US (1) US2423084A (ko)
CH (1) CH289545A (ko)
GB (1) GB609474A (ko)
NL (1) NL71657C (ko)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3562434A (en) * 1967-03-31 1971-02-09 Nippon Electric Co Interoffice signaling system employing selected ones of the touch-tone telephone frequencies for establishing interoffice connections

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1837003A (en) * 1927-08-09 1931-12-15 Reserve Holding Co Automatic telephone system
US1963747A (en) * 1934-06-19 Telephone system
US2269462A (en) * 1940-06-21 1942-01-13 Bell Telephone Labor Inc Telephone system
US2276037A (en) * 1940-09-07 1942-03-10 Bell Telephone Labor Inc Telephone system

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1963747A (en) * 1934-06-19 Telephone system
US1837003A (en) * 1927-08-09 1931-12-15 Reserve Holding Co Automatic telephone system
US2269462A (en) * 1940-06-21 1942-01-13 Bell Telephone Labor Inc Telephone system
US2276037A (en) * 1940-09-07 1942-03-10 Bell Telephone Labor Inc Telephone system

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3562434A (en) * 1967-03-31 1971-02-09 Nippon Electric Co Interoffice signaling system employing selected ones of the touch-tone telephone frequencies for establishing interoffice connections

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Publication number Publication date
CH289545A (fr) 1953-03-15
NL71657C (ko)
GB609474A (en) 1948-10-01

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