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GB1207339A - Loud speaking telephone circuits - Google Patents

Loud speaking telephone circuits

Info

Publication number
GB1207339A
GB1207339A GB5574067A GB5574067A GB1207339A GB 1207339 A GB1207339 A GB 1207339A GB 5574067 A GB5574067 A GB 5574067A GB 5574067 A GB5574067 A GB 5574067A GB 1207339 A GB1207339 A GB 1207339A
Authority
GB
United Kingdom
Prior art keywords
loud
amplifier
transistor
circuit
speaker
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
GB5574067A
Inventor
Arthur Herbert Patrick Baker
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 GB5574067A priority Critical patent/GB1207339A/en
Priority to US776136A priority patent/US3562791A/en
Priority to FR1602415D priority patent/FR1602415A/fr
Priority to NL6817583A priority patent/NL6817583A/xx
Priority to BE725117D priority patent/BE725117A/xx
Publication of GB1207339A publication Critical patent/GB1207339A/en
Expired legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03G—CONTROL OF AMPLIFICATION
    • H03G1/00—Details of arrangements for controlling amplification
    • H03G1/0005—Circuits characterised by the type of controlling devices operated by a controlling current or voltage signal
    • H03G1/0035—Circuits characterised by the type of controlling devices operated by a controlling current or voltage signal using continuously variable impedance elements
    • H03G1/0047—Circuits characterised by the type of controlling devices operated by a controlling current or voltage signal using continuously variable impedance elements using photo-electric elements
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03G—CONTROL OF AMPLIFICATION
    • H03G1/00—Details of arrangements for controlling amplification
    • H03G1/0005—Circuits characterised by the type of controlling devices operated by a controlling current or voltage signal
    • H03G1/0035—Circuits characterised by the type of controlling devices operated by a controlling current or voltage signal using continuously variable impedance elements
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03G—CONTROL OF AMPLIFICATION
    • H03G1/00—Details of arrangements for controlling amplification
    • H03G1/0005—Circuits characterised by the type of controlling devices operated by a controlling current or voltage signal
    • H03G1/0035—Circuits characterised by the type of controlling devices operated by a controlling current or voltage signal using continuously variable impedance elements
    • H03G1/0082—Circuits characterised by the type of controlling devices operated by a controlling current or voltage signal using continuously variable impedance elements using bipolar transistor-type devices
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03G—CONTROL OF AMPLIFICATION
    • H03G3/00—Gain control in amplifiers or frequency changers
    • H03G3/20—Automatic control
    • H03G3/30—Automatic control in amplifiers having semiconductor devices
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03G—CONTROL OF AMPLIFICATION
    • H03G3/00—Gain control in amplifiers or frequency changers
    • H03G3/20—Automatic control
    • H03G3/30—Automatic control in amplifiers having semiconductor devices
    • H03G3/3005—Automatic control in amplifiers having semiconductor devices in amplifiers suitable for low-frequencies, e.g. audio amplifiers
    • H03G3/301—Automatic control in amplifiers having semiconductor devices in amplifiers suitable for low-frequencies, e.g. audio amplifiers the gain being continuously variable
    • 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
    • H04M1/6033—Substation equipment, e.g. for use by subscribers including speech amplifiers for providing handsfree use or a loudspeaker mode in telephone sets
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04M—TELEPHONIC COMMUNICATION
    • H04M9/00—Arrangements for interconnection not involving centralised switching
    • H04M9/08—Two-way loud-speaking telephone systems with means for conditioning the signal, e.g. for suppressing echoes for one or both directions of traffic
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04M—TELEPHONIC COMMUNICATION
    • H04M9/00—Arrangements for interconnection not involving centralised switching
    • H04M9/08—Two-way loud-speaking telephone systems with means for conditioning the signal, e.g. for suppressing echoes for one or both directions of traffic
    • H04M9/10—Two-way loud-speaking telephone systems with means for conditioning the signal, e.g. for suppressing echoes for one or both directions of traffic with switching of direction of transmission by voice frequency

Landscapes

  • Engineering & Computer Science (AREA)
  • Signal Processing (AREA)
  • Multimedia (AREA)
  • Amplifiers (AREA)

Abstract

1,207,339. Loud-speaking telephones. STANDARD TELEPHONES & CABLES Ltd. 7 Dec., 1967, No. 55740/67. Headings H4K and H4R. In a loud-speaking telephone in which the signal levels in the incoming and outgoing channels are compared and the gains in the two channels differentially varied to favour the channel with the greater signal level A.G.C. is provided over the loud-speaker amplifier by the circuit of Fig. 2 in which a lamp 25 is fed with the loud-speaker amplifier output and illuminates a photo-sensitive resistor 56 controlling the bias on the base of a transistor T2 connected as one element of a potentiometer in the amplifier input. A further transistor 52 provides a variable amount of negative feedback over transistor T1 in the amplifier, the control potential for the transistor 52 being derived from the switching circuit (8, Fig. 1, not shown). The loud-speaker switching amplifier (10, Fig. 1) is fed via lead 38 with the loud-speaker channel signal after its amplitude has been stabilized by the A.G.C. circuit. The remainder of the circuit is as described in Specification 1,207,340.
GB5574067A 1967-12-07 1967-12-07 Loud speaking telephone circuits Expired GB1207339A (en)

Priority Applications (5)

Application Number Priority Date Filing Date Title
GB5574067A GB1207339A (en) 1967-12-07 1967-12-07 Loud speaking telephone circuits
US776136A US3562791A (en) 1967-12-07 1968-11-15 Loudspeaker telephone circuit arrangement
FR1602415D FR1602415A (en) 1967-12-07 1968-12-05
NL6817583A NL6817583A (en) 1967-12-07 1968-12-06
BE725117D BE725117A (en) 1967-12-07 1968-12-09

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB5574067A GB1207339A (en) 1967-12-07 1967-12-07 Loud speaking telephone circuits

Publications (1)

Publication Number Publication Date
GB1207339A true GB1207339A (en) 1970-09-30

Family

ID=10474756

Family Applications (1)

Application Number Title Priority Date Filing Date
GB5574067A Expired GB1207339A (en) 1967-12-07 1967-12-07 Loud speaking telephone circuits

Country Status (2)

Country Link
GB (1) GB1207339A (en)
NL (1) NL6817583A (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4434588A (en) 1980-09-10 1984-03-06 Honda Giken Kogyo Kabushiki Kaisha Honing head for high-speed operation
GB2209646A (en) * 1987-09-07 1989-05-17 Lake Electronic Tech Automatic volume control in loudspeaking telephone

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4434588A (en) 1980-09-10 1984-03-06 Honda Giken Kogyo Kabushiki Kaisha Honing head for high-speed operation
GB2209646A (en) * 1987-09-07 1989-05-17 Lake Electronic Tech Automatic volume control in loudspeaking telephone
GB2209646B (en) * 1987-09-07 1991-06-12 Lake Electronic Tech A speech circuit for a telephone

Also Published As

Publication number Publication date
NL6817583A (en) 1969-06-10

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Legal Events

Date Code Title Description
PS Patent sealed
PLNP Patent lapsed through nonpayment of renewal fees