GB1525964A - Telephone microphone - Google Patents
Telephone microphoneInfo
- 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
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
Landscapes
- Engineering & Computer Science (AREA)
- Signal Processing (AREA)
- Amplifiers (AREA)
- Audible-Bandwidth Dynamoelectric Transducers Other Than Pickups (AREA)
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.
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)
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 |
-
1975
- 1975-11-20 GB GB4776875A patent/GB1525964A/en not_active Expired
-
1976
- 1976-10-26 IE IE236276A patent/IE43640B1/en unknown
- 1976-10-29 NZ NZ18246076A patent/NZ182460A/en unknown
- 1976-11-12 AU AU19567/76A patent/AU500321B2/en not_active Expired
- 1976-11-19 ES ES453482A patent/ES453482A1/en not_active Expired
-
1979
- 1979-08-30 HK HK61379A patent/HK61379A/en unknown
Cited By (6)
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 |
---|---|
IE43640B1 (en) | 1981-04-22 |
AU500321B2 (en) | 1979-05-17 |
NZ182460A (en) | 1980-08-26 |
AU1956776A (en) | 1978-05-18 |
ES453482A1 (en) | 1977-11-16 |
HK61379A (en) | 1979-09-07 |
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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 |