GB1481750A - Subscriber line interface circuit - Google Patents

Subscriber line interface circuit

Info

Publication number
GB1481750A
GB1481750A GB4527575A GB4527575A GB1481750A GB 1481750 A GB1481750 A GB 1481750A GB 4527575 A GB4527575 A GB 4527575A GB 4527575 A GB4527575 A GB 4527575A GB 1481750 A GB1481750 A GB 1481750A
Authority
GB
United Kingdom
Prior art keywords
circuits
circuit
line
feed
voltage
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
Application number
GB4527575A
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.)
International Business Machines Corp
Original Assignee
International Business Machines 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.)
Filing date
Publication date
Priority to DE19752546477 priority Critical patent/DE2546477C2/en
Priority to FR7531773A priority patent/FR2288270A1/en
Application filed by International Business Machines Corp filed Critical International Business Machines Corp
Publication of GB1481750A publication Critical patent/GB1481750A/en
Expired legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04M—TELEPHONIC COMMUNICATION
    • H04M19/00—Current supply arrangements for telephone systems
    • H04M19/001—Current supply source at the exchanger providing current to substations
    • H04M19/005—Feeding arrangements without the use of line transformers

Landscapes

  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Signal Processing (AREA)
  • Devices For Supply Of Signal Current (AREA)
  • Interface Circuits In Exchanges (AREA)

Abstract

1481750 Automatic exchange systems INTERNATIONAL BUSINESS MACHINES CORP 31 Oct 1975 [23 Dec 1974] 45275/75 Heading H4K In a subscriber line circuit the wires of the line are connected respectively to earth and to a power supply terminal via individual feed circuits and each feed circuit includes a gyrator circuit and a capacitor, the combination exhibiting an inductive impedance which operates as a low pass circuit. The feed circuits 34, 35, Fig. 2, including the gyrator circuits, e.g. 34a, approximate to resistances for D.C. currents and to inductances each of value α=R3.R2C1 for A.C. currents. One of the circuits 35, Fig. 1, is connectable to one of two power supply terminals - 30 v., - 48 v., the voltage - 30 v. being applied if the handset is on hook, if ringing current is applied or if the line current is above an upper tolerance level, and the voltage - 48 v. being applied if the handset is off-hook and the line current is below a lower tolerance level. Where no varistor circuitry is included in the substation circuits components Z2, T3 and R5, Fig. 2, are omitted from each feed circuit and a changeover of supply voltage requires no modifications of these circuits. However if varistor circuitry is included it is necessary to maintain the line current constant on voltage changeover and transistor T3 is turned off by a signal B from the selection circuit when the voltage is switched to - 30 v. and the Zener diode Z2 acts to maintain the line current constant. Transistor T2 is switched on to inhibit the feed circuit during ringing, by using a signal RX derived from the selection circuit. A differential amplifier arrangement 44, 45 (Fig. 1) is used to eliminate echoes which may occur due to the signal S2 on line 18 being fed via the feed circuits 34, 35 to the line 26; the circuit 45 is therefore designed to simulate the feed circuits in this respect. Diode arrangements 36-38, 40-43 are used to limit signal amplitude levels. Components 19, 20 constitute the line terminating impedance.
GB4527575A 1974-10-18 1975-10-31 Subscriber line interface circuit Expired GB1481750A (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
DE19752546477 DE2546477C2 (en) 1974-10-18 1975-10-17 Ship tank for storing or transporting a pressurized flowable medium
FR7531773A FR2288270A1 (en) 1974-10-18 1975-10-17 Reservoirs for liquefied gases - for transport and storage under pressure with lobe-type compartmented tanks

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CH1722074A CH586984A5 (en) 1974-12-23 1974-12-23

Publications (1)

Publication Number Publication Date
GB1481750A true GB1481750A (en) 1977-08-03

Family

ID=4423697

Family Applications (1)

Application Number Title Priority Date Filing Date
GB4527575A Expired GB1481750A (en) 1974-10-18 1975-10-31 Subscriber line interface circuit

Country Status (6)

Country Link
JP (1) JPS5186904A (en)
CH (1) CH586984A5 (en)
DE (1) DE2551816C3 (en)
FR (1) FR2296339A1 (en)
GB (1) GB1481750A (en)
IT (1) IT1049925B (en)

Families Citing this family (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5413715A (en) * 1977-07-01 1979-02-01 Nippon Telegr & Teleph Corp <Ntt> Four-wire switching system
JPS5494811A (en) * 1978-01-11 1979-07-26 Hitachi Ltd Supply system for channel current
JPS5494810A (en) * 1978-01-11 1979-07-26 Hitachi Ltd Supply system for channel current
FR2414832A1 (en) * 1978-01-13 1979-08-10 Labo Cent Telecommunicat SUPPLY BRIDGE FOR TELEPHONE LINE
IT1159706B (en) * 1978-06-02 1987-03-04 Cselt Centro Studi Lab Telecom USER LINE ELECTRONIC TELEPHONE CIRCUIT
NL7810086A (en) * 1978-10-06 1980-04-09 Philips Nv POWER BRIDGE FOR A SUBSCRIBER FLOW.
US4254305A (en) * 1979-02-07 1981-03-03 International Telephone And Telegraph Corporation Current limited subscriber line feed circuit
FR2460078B1 (en) * 1979-06-25 1986-12-12 Trt Telecom Radio Electr ELECTRONIC SUBSCRIBER
CA1157175A (en) * 1981-02-20 1983-11-15 Mitel Corporation Power saving line circuit
DE3214624C2 (en) * 1982-04-20 1986-05-28 Siemens AG, 1000 Berlin und 8000 München Circuit arrangement for evaluating subscriber loop states in telephone systems, in particular in telephone branch exchange systems

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3649769A (en) * 1970-10-28 1972-03-14 Gen Electric Circuit for supplying direct current to a telephone line

Also Published As

Publication number Publication date
FR2296339A1 (en) 1976-07-23
DE2551816A1 (en) 1976-06-24
DE2551816B2 (en) 1979-06-13
CH586984A5 (en) 1977-04-15
JPS5619784B2 (en) 1981-05-09
DE2551816C3 (en) 1980-10-30
IT1049925B (en) 1981-02-10
JPS5186904A (en) 1976-07-30
FR2296339B1 (en) 1981-12-31

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Legal Events

Date Code Title Description
PS Patent sealed
PCNP Patent ceased through non-payment of renewal fee