GB936756A - Improvements in or relating to loudspeaking telephone systems - Google Patents

Improvements in or relating to loudspeaking telephone systems

Info

Publication number
GB936756A
GB936756A GB14915/61A GB1491561A GB936756A GB 936756 A GB936756 A GB 936756A GB 14915/61 A GB14915/61 A GB 14915/61A GB 1491561 A GB1491561 A GB 1491561A GB 936756 A GB936756 A GB 936756A
Authority
GB
United Kingdom
Prior art keywords
amplifier
transducer
switch
station
main station
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
GB14915/61A
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.)
Philips Electrical Industries Ltd
Original Assignee
Philips Electrical Industries Ltd
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 Philips Electrical Industries Ltd filed Critical Philips Electrical Industries Ltd
Publication of GB936756A publication Critical patent/GB936756A/en
Expired legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04M—TELEPHONIC COMMUNICATION
    • H04M9/00—Arrangements for interconnection not involving centralised switching
    • H04M9/001—Two-way communication systems between a limited number of parties
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
    • H02H3/08—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess current
    • H02H3/087—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess current for dc applications
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
    • H02H3/08—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess current
    • H02H3/093—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess current with timing means
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
    • H03F3/34—DC amplifiers in which all stages are DC-coupled
    • H03F3/343—DC amplifiers in which all stages are DC-coupled with semiconductor devices only
    • H03F3/345—DC amplifiers in which all stages are DC-coupled with semiconductor devices only with field-effect devices
    • H03F3/3455—DC amplifiers in which all stages are DC-coupled with semiconductor devices only with field-effect devices with junction-FET's
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03K—PULSE TECHNIQUE
    • H03K3/00—Circuits for generating electric pulses; Monostable, bistable or multistable circuits
    • H03K3/02—Generators characterised by the type of circuit or by the means used for producing pulses
    • H03K3/26—Generators characterised by the type of circuit or by the means used for producing pulses by the use, as active elements, of bipolar transistors with internal or external positive feedback
    • H03K3/28—Generators characterised by the type of circuit or by the means used for producing pulses by the use, as active elements, of bipolar transistors with internal or external positive feedback using means other than a transformer for feedback
    • H03K3/281—Generators characterised by the type of circuit or by the means used for producing pulses by the use, as active elements, of bipolar transistors with internal or external positive feedback using means other than a transformer for feedback using at least two transistors so coupled that the input of one is derived from the output of another, e.g. multivibrator
    • H03K3/286—Generators characterised by the type of circuit or by the means used for producing pulses by the use, as active elements, of bipolar transistors with internal or external positive feedback using means other than a transformer for feedback using at least two transistors so coupled that the input of one is derived from the output of another, e.g. multivibrator bistable
    • H03K3/2893—Bistables with hysteresis, e.g. Schmitt trigger

Landscapes

  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Signal Processing (AREA)
  • Electronic Switches (AREA)
  • Amplifiers (AREA)
  • Emergency Protection Circuit Devices (AREA)

Abstract

936,756. Intercommunication systems. PHILIPS ELECTRICAL INDUSTRIES Ltd. April 25, 1961 [April 28, 1960], No. 14915/61. Class 40 (4). A secrecy switch SK at a sub-station BP of a loud-speaking telephone system is operable to produce saturation of a transistor amplifier stage at the main station HP, thereby preventing conversation at the sub-station BP being overheard at the main station HP. A speak/ listen switch SL at the main station HP when in the position shown connects transducer LS.1 at the sub-station to the input of amplifier V and connects transducer LS.2 at the main station to the output of amplifier V, transducer LS.1 functioning as a microphone while transducer LS.2 functions as a loud-speaker. With switch SK open, battery B feeds saturation current to transistors T 1 , T 2 , thereby preventing conversation at sub-station BP being heard at main station HP. On closing switch SK a biasing potential from battery B is applied by voltage divider R 1 , R 2 to the base of transistor T 1 through a direct current path including line loop L 1 , L 2 and switch SK. A similar biasing potential, via resistors R 3 , R 5 , is applied to the base of transistor T 2 . Transistors T 1 , T 2 then function as amplifiers of microphone signals from transducer LS.1. Capacitor C 5 and resistor R 5 form a low pass filter for avoiding undesirable feedback effects. In the other position of switch SL, transducer LS.2 is connected to the input of amplifier V and functions as a microphone while transducer LS.1 is connected to the amplifier output and functions as a loudspeaker. Switch SK does not then affect the operation of amplifier V. The amplifier may have more than two stages. Only one stage may be put into a saturated state. More than two substations may be connected to the main station.
GB14915/61A 1959-06-11 1961-04-25 Improvements in or relating to loudspeaking telephone systems Expired GB936756A (en)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
CA701637T
GB20034/59A GB950182A (en) 1959-06-11 1959-06-11 Improvements in and relating to electrical circuits employing transistor networks
NL1127407X 1960-04-28
NL250981 1960-04-28

Publications (1)

Publication Number Publication Date
GB936756A true GB936756A (en) 1963-09-11

Family

ID=76269552

Family Applications (3)

Application Number Title Priority Date Filing Date
GB39319/63A Expired GB950183A (en) 1959-06-11 1959-06-11 Improvements in and relating to electrical circuits employing transistor networks
GB20034/59A Expired GB950182A (en) 1959-06-11 1959-06-11 Improvements in and relating to electrical circuits employing transistor networks
GB14915/61A Expired GB936756A (en) 1959-06-11 1961-04-25 Improvements in or relating to loudspeaking telephone systems

Family Applications Before (2)

Application Number Title Priority Date Filing Date
GB39319/63A Expired GB950183A (en) 1959-06-11 1959-06-11 Improvements in and relating to electrical circuits employing transistor networks
GB20034/59A Expired GB950182A (en) 1959-06-11 1959-06-11 Improvements in and relating to electrical circuits employing transistor networks

Country Status (6)

Country Link
JP (3) JPS384353B1 (en)
CA (1) CA701637A (en)
DE (2) DE1141333B (en)
FR (2) FR1259724A (en)
GB (3) GB950183A (en)
NL (1) NL250981A (en)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CH407212A (en) * 1963-08-29 1966-02-15 Siemens Ag Albis Amplitude discriminator with a bistable circuit
US3373295A (en) * 1965-04-27 1968-03-12 Aerojet General Co Memory element
SE435679B (en) * 1980-09-17 1984-10-15 Landskrona Finans Ab STIMULATOR SYSTEM, INCLUDING ONE OF A RECHARGEABLE BATTERY DRIVE PULSE GENERATOR

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1048946B (en) * 1957-07-19 1959-01-22 Siemens Ag Circuit arrangement for controlling the power supply to a consumer with, in particular, an inductive reactance component by means of a transistor

Also Published As

Publication number Publication date
JPS384354B1 (en) 1963-04-24
DE1127407B (en) 1962-04-12
FR1287248A (en) 1962-03-09
NL250981A (en)
GB950183A (en) 1964-02-19
GB950182A (en) 1964-02-19
JPS384353B1 (en) 1963-02-24
CA701637A (en) 1965-01-12
DE1141333B (en) 1962-12-20
FR1259724A (en) 1961-04-28
JPS3819521B1 (en) 1963-09-26

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