US3794782A - Pabx transmission and impulsing circuit - Google Patents

Pabx transmission and impulsing circuit Download PDF

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Publication number
US3794782A
US3794782A US00219241A US3794782DA US3794782A US 3794782 A US3794782 A US 3794782A US 00219241 A US00219241 A US 00219241A US 3794782D A US3794782D A US 3794782DA US 3794782 A US3794782 A US 3794782A
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US
United States
Prior art keywords
way
transformer
way speech
speech path
path
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US00219241A
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English (en)
Inventor
J Velik
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Alcatel Lucent NV
Original Assignee
International Standard Electric Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
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Publication date
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Assigned to ALCATEL N.V., DE LAIRESSESTRAAT 153, 1075 HK AMSTERDAM, THE NETHERLANDS, A CORP OF THE NETHERLANDS reassignment ALCATEL N.V., DE LAIRESSESTRAAT 153, 1075 HK AMSTERDAM, THE NETHERLANDS, A CORP OF THE NETHERLANDS ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: INTERNATIONAL STANDARD ELECTRIC CORPORATION, A CORP OF DE
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q3/00—Selecting arrangements
    • H04Q3/58—Arrangements providing connection between main exchange and sub-exchange or satellite
    • H04Q3/62—Arrangements providing connection between main exchange and sub-exchange or satellite for connecting to private branch exchanges
    • H04Q3/625—Arrangements in the private branch exchange
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04M—TELEPHONIC COMMUNICATION
    • H04M7/00—Arrangements for interconnection between switching centres
    • H04M7/0096—Trunk circuits
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q3/00—Selecting arrangements

Definitions

  • a circuit arrangement is provided for two-way speech transmission and one-way impulse transmission in telecommunication exchanges. Transmission is across a transformer having first and second windings series connected to, but D.C. isolated from, first and second two-way speech paths respectively. Amplifier means is coupled through additional windings of the trans former to compensate for the attenuation of signals between the two speech paths due to natural transformer losses.
  • a source of regulated DC. power provides energy to the first two-way speech path and to an impulse repeater circuit coupled thereto. The repeater circuit provides substantially identical impulses to the second two-way speech path.
  • the present invention has achieved a minimum return loss figure of dB, while insertion loss on a 600 ohm line has bettered the range 0.8 1.0 dB over 0.3 3.4 kHz.
  • a circuit arrangement for two-way speech transmission and one way impulse transmission in telecommunication exchanges employs a transformer having first and second windings series connected to, but DO isolated from, first and second two-way speech paths respectively.
  • Amplifier means is provided in association with the transformer to substantially compensate the attenuation of signals between the two speech paths due to natural transformer losses.
  • a source of regulated DC. power is used to supply the first two-way speech path.
  • the DC. power is also applied to impulse repeater circuit means which is connected with the first two way speech path and which upon the detection of impulses therefrom causes substantially identical impulses to be generated in the second two-way speech path.
  • a subscribers telephone subset is connected to the terminals A, B.
  • Energy from a D..C. source is provided to the subset from the battery VI via a series standard regulator l (dotted enclosure) over terminal a of relay 2.
  • the circuit of the series regulator is of a standard form and will be recognized by those skilled in the art and therefore requires no further description other than the fact that it comprises the familiar Darlington pair-zener diode arrangement. From terminal a of relay 2 current flows through the winding to terminal b, through diode D1 and the parallel combination of bias resistor R1 and the emitter-base circuit of transistor T1 to terminal d of inductor L1.
  • T1 is protected from large inverse voltages by the presence of diodes D1 and D2.
  • Dialling pulses from the extension are set up by opening and closing the current loop of the extension circuit and these pulses are detected by the series transistor T1 whose output is fed to the base of transistor T2 via resistor R2.
  • T2 is chosen as a high gain transistor so that alternately it rapidly saturates and cuts-off in unison with the dialling pulse signal fed to its base.
  • the emitter of T2 is held, say, at 4.5 volts by [both the zener diode Z1 and resistor R3 and, when the transistoris thrown into saturation, current flowsfrom the supply through the series-connectedwindings of the relay 3, resistor R4, collector-emitter path of T2 and to ground via Z1.
  • Resistor R5 is used to establish base bias on T2 as well as performing the load function for T1 while Z1 also serves to prevent conduction in T2 due to small leakage currents flowing across terminals A, B.
  • the dialling impulses driving T1 are substantially square-shaped this being ensured by the presence of capacitor C1 which cancels the effect of the back e.m.f. from L1 on the pulse detection integrity of Tl.
  • Transformer 4 is D.C. isolated from the circuits described above by the series capacitor C2 which provides very low impedance to AC. signals for transmission along the speech path.
  • the dialling pulses are transmitted to the exchange from operation of relay 3 by its associated contact 5 via the closed contact 6 which is held closed by a relay (not shown) at the time the extension is brought into circuit.
  • Contact 6 is opened in standard] P.A.B.X. function when the called extension answers thus removing the short across the speech circuit between C,D via transformer 4.
  • contact 5 is held closed completing the speech path to C.
  • spark quenching of contact 5 is achieved by the series combination of R6 and C3.
  • the battery supply is via an inductive element and hence the inclusion of L1.
  • the audio signals from the extension are balanced and, as capacitor C2 has negligible impedance in the audio frequency spectrum, the full signal appears across the j-k winding of transformer 4, which being a 1:] transformer allows the signal to appear unattenuated across winding l-m. We are assuming at this stage that negligible transformer losses are involved. Transmission to the exchange is through the bridge network D3, D4, D5, D6 and closed contact to terminals C,D.
  • Capacitor C4 like C2, offers near zero impedance at audio frequencies and serves to isolate the exchange direct current from transformer 4.
  • resistor R7 is located across the transformer side of the bridge network in series with contact 7 of relay 8 which in turn is in parallel with both R7 and contact 7.
  • exchange current relay 8 which is very inductive and therefore presents negligible A.C. load to the line, will operate and remove R7 from the circuit by opening contact 7.
  • a purpose of the diode bridge D3-D6 is to aid in the prevention of large impulse voltages being generated from the inductive line and from relay 8 either during impulsing or when there is a test reversal on the exchange line. That is, the bridge ensures that D.C. through relay 8 is always in the same direction regardless of test reversals or an incorrectly poled exchange; the back e.m.f. would be considerably greater from relay 8 if the direction of DC. current were changed.
  • relay 2 is differentially wound as indicated in the drawing so that it will not operate unless the extension is unbalanced or an earth is applied to the terminals A,B.
  • the provision of this relay is for certain P.A.B.X. functions, as will be recognized by telephone engineers, and does not, per se, form part of the inventive content.
  • transformer 4 it will be realized that in practice it is not a lossless component and the assumption made earlier in this specification requires qualification.
  • transformer loss-reduction amplifier comprises zener diode Z3 and diode D6, which guard the transistor T3 against harmful voltages generated during impulsing or test reversal onthe exchange line, and capacitor C5 to prevent high frequency oscillation. It has been found that this type of amplifier arrangement coupled to transformer 4 closely approximates an ideal 1:1 lossless transformer suitable for P.A.B.X. application.
  • a circuit arrangement for two-way speech transmissions and one-way impulse transmission in telecommunication exchanges comprising a first two-way speech path, a second two-way speech path, a transformer having first and second windings series connected between said first and second two-way speech paths, means providing DC isolation between said transformer windings and said two-way speech paths, third and fourth windings coupled to said transformer, means coupling the third winding to amplifier means to provide a correction signal and means amplifying said correction signal to the fourth winding of the transformer to substantially compensate for the attenuation of signals between the two speech paths due to natural transformer losses, means coupling a source of regulated DC.
  • an impulse repeater circuit connected to said first twoway path and to said source of DC power to respond to impulses in said first two-way path to cause changes including closure of relay contacts in the second two-way speech path causing substantially identical impulses to appear in the second two-way speech path.
  • the impulse repeater circuit includes a first transistor coupled to respond to DC dial pulses and supply operate signals, a relay, a second transistor coupled to said first transistor and to said relay to respond to said operate signals to provide control signals to said relay and cause operation of contacts of said relay in said second two-way speech path to thereby provide pulses to said second two-way speech path.
  • said means providing DC isolation includes first and second capacitors, means coupling said first capacitor in series between the first winding of said transformer and the first two-way speech path, and means coupling said second capacitor in series between the second winding of said transformer and the second

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Physics & Mathematics (AREA)
  • Astronomy & Astrophysics (AREA)
  • General Physics & Mathematics (AREA)
  • Interface Circuits In Exchanges (AREA)
  • Devices For Supply Of Signal Current (AREA)
  • Cable Transmission Systems, Equalization Of Radio And Reduction Of Echo (AREA)
US00219241A 1971-01-20 1972-01-20 Pabx transmission and impulsing circuit Expired - Lifetime US3794782A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
AU375971 1971-01-20

Publications (1)

Publication Number Publication Date
US3794782A true US3794782A (en) 1974-02-26

Family

ID=3694228

Family Applications (1)

Application Number Title Priority Date Filing Date
US00219241A Expired - Lifetime US3794782A (en) 1971-01-20 1972-01-20 Pabx transmission and impulsing circuit

Country Status (7)

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US (1) US3794782A (es)
BE (1) BE778262A (es)
CA (1) CA951444A (es)
DE (1) DE2201986A1 (es)
ES (1) ES399050A1 (es)
FR (1) FR2122947A5 (es)
IT (1) IT946689B (es)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5940358B2 (ja) * 1978-10-18 1984-09-29 日本電信電話株式会社 通話路スイツチ回路
DE3804216A1 (de) * 1988-02-11 1989-08-24 Telefonbau & Normalzeit Gmbh Schaltungsanordnung fuer eine externleitungsuebertragung von kommunikations-vermittlungsanlagen, insbesondere fernsprechnebenstellenanlagen

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3166642A (en) * 1961-12-21 1965-01-19 Bell Telephone Labor Inc Signaling arrangement
US3474355A (en) * 1965-02-08 1969-10-21 Siemens Ag Circuit for decreasing characteristic losses of inductors

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3166642A (en) * 1961-12-21 1965-01-19 Bell Telephone Labor Inc Signaling arrangement
US3474355A (en) * 1965-02-08 1969-10-21 Siemens Ag Circuit for decreasing characteristic losses of inductors

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
Basic Electronics; 1968; p. 68. *
GE Transistor Manual; 1969; p. 228. *

Also Published As

Publication number Publication date
DE2201986A1 (de) 1972-08-10
BE778262A (fr) 1972-07-20
CA951444A (en) 1974-07-16
IT946689B (it) 1973-05-21
FR2122947A5 (es) 1972-09-01
ES399050A1 (es) 1974-10-16

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Legal Events

Date Code Title Description
AS Assignment

Owner name: ALCATEL N.V., DE LAIRESSESTRAAT 153, 1075 HK AMSTE

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:INTERNATIONAL STANDARD ELECTRIC CORPORATION, A CORP OF DE;REEL/FRAME:004718/0023

Effective date: 19870311