FR2233770A1 - Protection of communication circuit - is for use with microphone and comprises two diodes mounted in series with microphone - Google Patents

Protection of communication circuit - is for use with microphone and comprises two diodes mounted in series with microphone

Info

Publication number
FR2233770A1
FR2233770A1 FR7321189A FR7321189A FR2233770A1 FR 2233770 A1 FR2233770 A1 FR 2233770A1 FR 7321189 A FR7321189 A FR 7321189A FR 7321189 A FR7321189 A FR 7321189A FR 2233770 A1 FR2233770 A1 FR 2233770A1
Authority
FR
France
Prior art keywords
microphone
impedance
series
protection
communication circuit
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
FR7321189A
Other languages
French (fr)
Other versions
FR2233770B1 (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.)
Charbonnages de France CDF
Original Assignee
Charbonnages de France CDF
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 Charbonnages de France CDF filed Critical Charbonnages de France CDF
Priority to FR7321189A priority Critical patent/FR2233770A1/en
Publication of FR2233770A1 publication Critical patent/FR2233770A1/en
Application granted granted Critical
Publication of FR2233770B1 publication Critical patent/FR2233770B1/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
    • H04M1/02—Constructional features of telephone sets
    • H04M1/19—Arrangements of transmitters, receivers, or complete sets to prevent eavesdropping, to attenuate local noise or to prevent undesired transmission; Mouthpieces or receivers specially adapted therefor

Landscapes

  • Engineering & Computer Science (AREA)
  • Signal Processing (AREA)
  • Filters And Equalizers (AREA)

Abstract

The antilocal protection circuit used with telephone handsets fails to operate satisfactorily when used where noise is of the order of 90 dB. A microphone (M) is connected through a voltage amplifier (A) to the primary of a transformer (T). An ear piece (E) is connected to the centre tap (1) of the secondary winding and to the junction (2) of an impedance (Z) with the line (L). The other end of the impedance is connected to the transformer secondary winding and is meant to have a value equal to the line impedance to eliminate noise from the microphone. Two germanium diodes (or transistors) mounted back to back (D) are connected in series with the microphone. Their dynamic impedance increases with increased applied voltage thus enabling speech transmission in noisy environments.
FR7321189A 1973-06-12 1973-06-12 Protection of communication circuit - is for use with microphone and comprises two diodes mounted in series with microphone Granted FR2233770A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
FR7321189A FR2233770A1 (en) 1973-06-12 1973-06-12 Protection of communication circuit - is for use with microphone and comprises two diodes mounted in series with microphone

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
FR7321189A FR2233770A1 (en) 1973-06-12 1973-06-12 Protection of communication circuit - is for use with microphone and comprises two diodes mounted in series with microphone

Publications (2)

Publication Number Publication Date
FR2233770A1 true FR2233770A1 (en) 1975-01-10
FR2233770B1 FR2233770B1 (en) 1976-04-23

Family

ID=9120786

Family Applications (1)

Application Number Title Priority Date Filing Date
FR7321189A Granted FR2233770A1 (en) 1973-06-12 1973-06-12 Protection of communication circuit - is for use with microphone and comprises two diodes mounted in series with microphone

Country Status (1)

Country Link
FR (1) FR2233770A1 (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2502370A1 (en) * 1981-03-18 1982-09-24 Trt Telecom Radio Electr NOISE REDUCTION DEVICE IN A SPEECH SIGNAL MELEUR OF NOISE

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2502370A1 (en) * 1981-03-18 1982-09-24 Trt Telecom Radio Electr NOISE REDUCTION DEVICE IN A SPEECH SIGNAL MELEUR OF NOISE

Also Published As

Publication number Publication date
FR2233770B1 (en) 1976-04-23

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Legal Events

Date Code Title Description
ST Notification of lapse