GB928091A - Loud-speaking telephone systems, particularly for use in mines - Google Patents

Loud-speaking telephone systems, particularly for use in mines

Info

Publication number
GB928091A
GB928091A GB3470959A GB3470959A GB928091A GB 928091 A GB928091 A GB 928091A GB 3470959 A GB3470959 A GB 3470959A GB 3470959 A GB3470959 A GB 3470959A GB 928091 A GB928091 A GB 928091A
Authority
GB
United Kingdom
Prior art keywords
mines
loud
telephone systems
handset
oct
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
GB3470959A
Inventor
John Angus Leslie
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.)
Associated Electrical Industries Ltd
Original Assignee
Associated 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 Associated Electrical Industries Ltd filed Critical Associated Electrical Industries Ltd
Priority to GB3470959A priority Critical patent/GB928091A/en
Publication of GB928091A publication Critical patent/GB928091A/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

Landscapes

  • Engineering & Computer Science (AREA)
  • Signal Processing (AREA)
  • Interconnected Communication Systems, Intercoms, And Interphones (AREA)

Abstract

928,091. Two-station systems. ASSOCIATED ELECTRICAL INDUSTRIES Ltd. Oct. 25, 1960 [Oct. 13, 1959], No. 34709/59. Class 40 (4). In a system particularly for use in mines having two stations connected by a 2-wire line 6, there is provided at each station a loudspeaker 5 used primarily for calling, this and the earpiece 3 of the handset being connected normally to the output of the local amplifier 4. Upon removal of the handset from the hook 7 the loud-speaker 5 is disconnected and D.C. is applied to relay 16 at both stations to energize the amplifiers, which may be of the transistor type. The circuit may be modified to avoid side-tone.
GB3470959A 1959-10-13 1959-10-13 Loud-speaking telephone systems, particularly for use in mines Expired GB928091A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB3470959A GB928091A (en) 1959-10-13 1959-10-13 Loud-speaking telephone systems, particularly for use in mines

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB3470959A GB928091A (en) 1959-10-13 1959-10-13 Loud-speaking telephone systems, particularly for use in mines

Publications (1)

Publication Number Publication Date
GB928091A true GB928091A (en) 1963-06-06

Family

ID=10369000

Family Applications (1)

Application Number Title Priority Date Filing Date
GB3470959A Expired GB928091A (en) 1959-10-13 1959-10-13 Loud-speaking telephone systems, particularly for use in mines

Country Status (1)

Country Link
GB (1) GB928091A (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4064366A (en) * 1976-01-15 1977-12-20 Winster Engineering Group Limited Intrinsically safe telephone systems
US4214127A (en) * 1977-05-18 1980-07-22 S.I.L.E.C.-Division Signalisation Industrielle Intrinsically safe telephone network

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4064366A (en) * 1976-01-15 1977-12-20 Winster Engineering Group Limited Intrinsically safe telephone systems
US4214127A (en) * 1977-05-18 1980-07-22 S.I.L.E.C.-Division Signalisation Industrielle Intrinsically safe telephone network

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