GB1525964A - Telephone microphone - Google Patents

Telephone microphone

Info

Publication number
GB1525964A
GB1525964A GB4776875A GB4776875A GB1525964A GB 1525964 A GB1525964 A GB 1525964A GB 4776875 A GB4776875 A GB 4776875A GB 4776875 A GB4776875 A GB 4776875A GB 1525964 A GB1525964 A GB 1525964A
Authority
GB
United Kingdom
Prior art keywords
feedback
stage
amplifier
protection against
microphone
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
GB4776875A
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.)
STC PLC
Original Assignee
Standard Telephone and Cables PLC
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 Standard Telephone and Cables PLC filed Critical Standard Telephone and Cables PLC
Priority to GB4776875A priority Critical patent/GB1525964A/en
Priority to IE236276A priority patent/IE43640B1/en
Priority to NZ18246076A priority patent/NZ182460A/en
Priority to AU19567/76A priority patent/AU500321B2/en
Priority to ES453482A priority patent/ES453482A1/en
Publication of GB1525964A publication Critical patent/GB1525964A/en
Priority to HK61379A priority patent/HK61379A/en
Expired 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
    • H04M1/60—Substation equipment, e.g. for use by subscribers including speech amplifiers
    • H04M1/6008—Substation equipment, e.g. for use by subscribers including speech amplifiers in the transmitter circuit

Abstract

1525964 Moving coil microphone circuits STANDARD TELEPHONES & CABLES Ltd 20 Nov 1975 47768/75 Heading H4J A microphone assembly adapted to be fitted to a telephone subscriber's instrument includes a moving coil transducer and a two-stage D.C. coupled amplifier for matching the transducer impedance to line. The microphone assembly is preferably arranged to have an electrical output similar to that of a carbon microphone. The transducer (11), Fig. 1, not shown, together with the amplifier (12), is mounted on a circuit board (13) and fits into a housing of a conventional telephone transmitter. The amplifier (Fig. 2) includes transistors V 1 , V 2 , V 3 forming a two-stage D.C. coupled amplifier with full D.C. and partial A.C. feedback. Transistor V 1 acts as a common emitter and amplified signals appear across collector resistor R 3 . The signal then passes to the base of compound common emitter V 2 , V 3 , the resulting amplified output appearing across R 5 and R 6 and the load at terminals T 1 , T 2 . Overall D.C. feedback is provided by R, and R 2 . The A.C. feedback provided by resistors R 1 and R 2 is decoupled by capacitor C 1 in the frequency band 300 Hz to 3À4 kHz. The only local emitter A.C. feedback is operating for the first stage gain stabilization. The gain of the second stage is more closely defined by resistors R 3 and R 4 . Protection against polarity reversal is provided by diodes V 6 and V 7 and Zener diodes V 4 and V 5 operating in the forward mode. Protection against short term overload (e.g. ring-trip failure) is provided by V 4 , V 5 and R 5 causing either V 4 or V 5 to conduct before the current can reach a value sufficient to exceed the capabilities of V 3 . High voltage transients (e.g. due to lightning) is provided by resistor R 6 and Zener diodes V 4 and V 5 . Capacitor C 2 provides some protection against R.F.I.
GB4776875A 1975-11-20 1975-11-20 Telephone microphone Expired GB1525964A (en)

Priority Applications (6)

Application Number Priority Date Filing Date Title
GB4776875A GB1525964A (en) 1975-11-20 1975-11-20 Telephone microphone
IE236276A IE43640B1 (en) 1975-11-20 1976-10-26 Telephone microphone
NZ18246076A NZ182460A (en) 1975-11-20 1976-10-29 Line powered moving coil microphone circuit
AU19567/76A AU500321B2 (en) 1975-11-20 1976-11-12 Telephone microphone
ES453482A ES453482A1 (en) 1975-11-20 1976-11-19 Telephone microphone
HK61379A HK61379A (en) 1975-11-20 1979-08-30 Telephone microphone

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB4776875A GB1525964A (en) 1975-11-20 1975-11-20 Telephone microphone

Publications (1)

Publication Number Publication Date
GB1525964A true GB1525964A (en) 1978-09-27

Family

ID=10446188

Family Applications (1)

Application Number Title Priority Date Filing Date
GB4776875A Expired GB1525964A (en) 1975-11-20 1975-11-20 Telephone microphone

Country Status (6)

Country Link
AU (1) AU500321B2 (en)
ES (1) ES453482A1 (en)
GB (1) GB1525964A (en)
HK (1) HK61379A (en)
IE (1) IE43640B1 (en)
NZ (1) NZ182460A (en)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4326106A (en) * 1979-02-03 1982-04-20 Licentia Patent-Verwaltungs Gmbh Telephone amplifier circuit
FR2494530A1 (en) * 1980-11-17 1982-05-21 Horlogerie Photograph Fse TELEPHONE STATION COMPRISING A CARRIER CURRENT PREAMPLIFIER, A MIC CUTTING SWITCH AND A DEVICE FOR SIGNALING THIS CUT
EP0108228A2 (en) * 1982-11-08 1984-05-16 Sodeco-Saia Ag Telephone set with low energy consumption
GB2142504A (en) * 1983-06-28 1985-01-16 Gibson Dawson Joseph Microphone

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4326106A (en) * 1979-02-03 1982-04-20 Licentia Patent-Verwaltungs Gmbh Telephone amplifier circuit
FR2494530A1 (en) * 1980-11-17 1982-05-21 Horlogerie Photograph Fse TELEPHONE STATION COMPRISING A CARRIER CURRENT PREAMPLIFIER, A MIC CUTTING SWITCH AND A DEVICE FOR SIGNALING THIS CUT
EP0052347A1 (en) * 1980-11-17 1982-05-26 Horlogerie Photographique Francaise Telephone apparatus provided with a preamplifier with carrier current, an interrupter for disconnection of the microphone and a device for signalling this disconnection
EP0108228A2 (en) * 1982-11-08 1984-05-16 Sodeco-Saia Ag Telephone set with low energy consumption
EP0108228A3 (en) * 1982-11-08 1984-06-13 Sodeco-Saia Ag Telephone set with low energy consumption
GB2142504A (en) * 1983-06-28 1985-01-16 Gibson Dawson Joseph Microphone

Also Published As

Publication number Publication date
HK61379A (en) 1979-09-07
ES453482A1 (en) 1977-11-16
IE43640B1 (en) 1981-04-22
AU1956776A (en) 1978-05-18
AU500321B2 (en) 1979-05-17
NZ182460A (en) 1980-08-26

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Legal Events

Date Code Title Description
PS Patent sealed
746 Register noted 'licences of right' (sect. 46/1977)
PCNP Patent ceased through non-payment of renewal fee