GB540089A - Improvements in and relating to electrical communication systems - Google Patents

Improvements in and relating to electrical communication systems

Info

Publication number
GB540089A
GB540089A GB553240A GB553240A GB540089A GB 540089 A GB540089 A GB 540089A GB 553240 A GB553240 A GB 553240A GB 553240 A GB553240 A GB 553240A GB 540089 A GB540089 A GB 540089A
Authority
GB
United Kingdom
Prior art keywords
line
telephone
relating
communication systems
electrical communication
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
GB553240A
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.)
Telephone Manufacturing Co Ltd
Original Assignee
Telephone Manufacturing Co 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 Telephone Manufacturing Co Ltd filed Critical Telephone Manufacturing Co Ltd
Priority to GB553240A priority Critical patent/GB540089A/en
Publication of GB540089A publication Critical patent/GB540089A/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
    • H04M1/68—Circuit arrangements for preventing eavesdropping

Landscapes

  • Engineering & Computer Science (AREA)
  • Signal Processing (AREA)
  • Telephone Set Structure (AREA)

Abstract

540,089. Secret telephony. TELEPHONE MANUFACTURING CO., Ltd., and PADDLE, L. H. March 27, 1940, No. 5532. [Class 40 (iv)] Telephone subscribers have two lines connected alternatively to a single handset according as secret or plain communication is desired. The line N for normal communication is connected direct to the calling jack, the other line S is connected to the jack via secrecy apparatus SE1 or SE2 by means of switches A ... D which are interlocked to prevent crossed connections. The switch by which the subscriber connects himself to the desired line may be on the micro-telephone. Lamps L1, L2 indicate which secrecy apparatus is in use. Specifications 531,318 and 536,945 are referred to.
GB553240A 1940-03-27 1940-03-27 Improvements in and relating to electrical communication systems Expired GB540089A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB553240A GB540089A (en) 1940-03-27 1940-03-27 Improvements in and relating to electrical communication systems

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB553240A GB540089A (en) 1940-03-27 1940-03-27 Improvements in and relating to electrical communication systems

Publications (1)

Publication Number Publication Date
GB540089A true GB540089A (en) 1941-10-06

Family

ID=9797976

Family Applications (1)

Application Number Title Priority Date Filing Date
GB553240A Expired GB540089A (en) 1940-03-27 1940-03-27 Improvements in and relating to electrical communication systems

Country Status (1)

Country Link
GB (1) GB540089A (en)

Similar Documents

Publication Publication Date Title
ES409258A1 (en) Central office private branch exchange telephone system
GB540089A (en) Improvements in and relating to electrical communication systems
GB522457A (en) Improvements in or relating to systems of simultaneous telephony on a number of lines
US2278410A (en) Telephone system
JPS54154202A (en) Talking protective circuit for multi-telephone
US2338997A (en) Communication system
GB1167764A (en) Telephone Exchange
GB1490869A (en) Subscriber station for telephone systems
GB536945A (en) Improvements in telephone systems
US2042828A (en) Telephone system
US2844657A (en) Multipled key-ended trunk termination
US2532889A (en) Tie line circuit arrangement
JPS51144503A (en) Telephone set
Davidson Toll switchboard no. 3
GB1043839A (en) Method to mark calls in telephone connections, equipped with automatic call transfer
GB559438A (en) Improvements relating to telephone systems
GB475952A (en) Improvements in and relating to telephone systems
GB323090A (en) Improvements in and relating to telephone systems
JPS57147367A (en) Conference trunk
GB531318A (en) Improvements in and relating to electric communication systems
JPS5437609A (en) Extension call system
GB790609A (en) Improvements in and relating to manual telephone exchange systems
JPS6462948A (en) System for changing extension number in private telephone
JPS5628594A (en) Main wire originating control method
GB1087785A (en) Improvements in and relating to manual telephone exchange systems