GB1481750A - Subscriber line interface circuit - Google Patents
Subscriber line interface circuitInfo
- 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
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.
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)
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)
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 |
-
1974
- 1974-12-23 CH CH1722074A patent/CH586984A5/xx not_active IP Right Cessation
-
1975
- 1975-10-31 GB GB4527575A patent/GB1481750A/en not_active Expired
- 1975-11-10 FR FR7535236A patent/FR2296339A1/en active Granted
- 1975-11-19 DE DE19752551816 patent/DE2551816C3/en not_active Expired
- 1975-11-28 IT IT2975975A patent/IT1049925B/en active
- 1975-12-19 JP JP15069275A patent/JPS5186904A/en active Granted
Also Published As
Publication number | Publication date |
---|---|
IT1049925B (en) | 1981-02-10 |
FR2296339B1 (en) | 1981-12-31 |
DE2551816A1 (en) | 1976-06-24 |
DE2551816B2 (en) | 1979-06-13 |
CH586984A5 (en) | 1977-04-15 |
FR2296339A1 (en) | 1976-07-23 |
JPS5619784B2 (en) | 1981-05-09 |
JPS5186904A (en) | 1976-07-30 |
DE2551816C3 (en) | 1980-10-30 |
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Legal Events
Date | Code | Title | Description |
---|---|---|---|
PS | Patent sealed | ||
PCNP | Patent ceased through non-payment of renewal fee |