FR2279283A1 - Numerical telephone keyboard terminal - has numerical vocal frequency generator and filter to obtain sinusoidal signals - Google Patents

Numerical telephone keyboard terminal - has numerical vocal frequency generator and filter to obtain sinusoidal signals

Info

Publication number
FR2279283A1
FR2279283A1 FR7425197A FR7425197A FR2279283A1 FR 2279283 A1 FR2279283 A1 FR 2279283A1 FR 7425197 A FR7425197 A FR 7425197A FR 7425197 A FR7425197 A FR 7425197A FR 2279283 A1 FR2279283 A1 FR 2279283A1
Authority
FR
France
Prior art keywords
numerical
switching circuit
frequency generator
transistor
filter
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.)
Granted
Application number
FR7425197A
Other languages
French (fr)
Other versions
FR2279283B1 (en
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 Enterprise SA
Original Assignee
Telic Alcatel SA
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
Application filed by Telic Alcatel SA filed Critical Telic Alcatel SA
Priority to FR7425197A priority Critical patent/FR2279283A1/en
Publication of FR2279283A1 publication Critical patent/FR2279283A1/en
Application granted granted Critical
Publication of FR2279283B1 publication Critical patent/FR2279283B1/fr
Granted legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04M—TELEPHONIC COMMUNICATION
    • H04M1/00—Substation equipment, e.g. for use by subscribers
    • H04M1/26—Devices for calling a subscriber
    • H04M1/30—Devices which can set up and transmit only one digit at a time
    • H04M1/50—Devices which can set up and transmit only one digit at a time by generating or selecting currents of predetermined frequencies or combinations of frequencies

Landscapes

  • Engineering & Computer Science (AREA)
  • Signal Processing (AREA)
  • Devices For Supply Of Signal Current (AREA)

Abstract

A keyboard terminal has a voice frequency generator controlled by a time base and has a filter to transform the logic signals into sinusoidal current at voice frequencies. Switching circuits are controlled by signals (AS, AS) from the frequency generator (GF). The first switching circuit has a transistor (T2) in parallel with another transistor (T1) of a current generator. The second switching circuit has a transistor (T4) in parallel with the primary of a transformer (T). The third switching circuit has a transistor (T3) in parallel with a microphone. The first switching circuit disconnects the generator (GF) during normal conversation, the second circuit short-circuits the transformer to reject keyboard frequencies and allow good listening and the third switching circuit short-circuits the microphone during the numbering phase and avoid false numberS.
FR7425197A 1974-07-19 1974-07-19 Numerical telephone keyboard terminal - has numerical vocal frequency generator and filter to obtain sinusoidal signals Granted FR2279283A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
FR7425197A FR2279283A1 (en) 1974-07-19 1974-07-19 Numerical telephone keyboard terminal - has numerical vocal frequency generator and filter to obtain sinusoidal signals

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
FR7425197A FR2279283A1 (en) 1974-07-19 1974-07-19 Numerical telephone keyboard terminal - has numerical vocal frequency generator and filter to obtain sinusoidal signals

Publications (2)

Publication Number Publication Date
FR2279283A1 true FR2279283A1 (en) 1976-02-13
FR2279283B1 FR2279283B1 (en) 1976-12-24

Family

ID=9141498

Family Applications (1)

Application Number Title Priority Date Filing Date
FR7425197A Granted FR2279283A1 (en) 1974-07-19 1974-07-19 Numerical telephone keyboard terminal - has numerical vocal frequency generator and filter to obtain sinusoidal signals

Country Status (1)

Country Link
FR (1) FR2279283A1 (en)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0016950A1 (en) * 1979-02-21 1980-10-15 Licentia Patent-Verwaltungs-GmbH Circuit arrangement for switch-over between voice frequency signalling and speech, and vice-versa, in telecommunication apparatus
FR2478411A1 (en) * 1980-03-17 1981-09-18 Telephonie Ind Commerciale Interchangeable multifrequency telephone keyboard - has diode bridge across protection device, with supply and switching circuit connected to negative bridge terminal
FR2480051A1 (en) * 1980-04-02 1981-10-09 Telephonie Ind Commerciale Pushbutton keyboard for telephone - uses frequency generator supplied by pair of zener diodes and current source with current limiting circuit
US4496799A (en) * 1982-12-13 1985-01-29 International Telephone And Telegraph Corporation Handsfree telephone instrument using digital dial
WO1990009715A1 (en) * 1989-02-18 1990-08-23 Robert Bosch Gmbh Circuit arrangement for a telephone subscriber station

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0016950A1 (en) * 1979-02-21 1980-10-15 Licentia Patent-Verwaltungs-GmbH Circuit arrangement for switch-over between voice frequency signalling and speech, and vice-versa, in telecommunication apparatus
FR2478411A1 (en) * 1980-03-17 1981-09-18 Telephonie Ind Commerciale Interchangeable multifrequency telephone keyboard - has diode bridge across protection device, with supply and switching circuit connected to negative bridge terminal
FR2480051A1 (en) * 1980-04-02 1981-10-09 Telephonie Ind Commerciale Pushbutton keyboard for telephone - uses frequency generator supplied by pair of zener diodes and current source with current limiting circuit
US4496799A (en) * 1982-12-13 1985-01-29 International Telephone And Telegraph Corporation Handsfree telephone instrument using digital dial
WO1990009715A1 (en) * 1989-02-18 1990-08-23 Robert Bosch Gmbh Circuit arrangement for a telephone subscriber station

Also Published As

Publication number Publication date
FR2279283B1 (en) 1976-12-24

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Legal Events

Date Code Title Description
ST Notification of lapse