GB531318A - Improvements in and relating to electric communication systems - Google Patents

Improvements in and relating to electric communication systems

Info

Publication number
GB531318A
GB531318A GB1883739A GB1883739A GB531318A GB 531318 A GB531318 A GB 531318A GB 1883739 A GB1883739 A GB 1883739A GB 1883739 A GB1883739 A GB 1883739A GB 531318 A GB531318 A GB 531318A
Authority
GB
United Kingdom
Prior art keywords
handset
instrument
line
normal
relating
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
GB1883739A
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 GB1883739A priority Critical patent/GB531318A/en
Publication of GB531318A publication Critical patent/GB531318A/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

531,318. Secret transmission. TELEPHONE MANUFACTURING CO., Ltd., and PADDLE, L. H. June 28, 1939, No. 18837. [Class 40 (iv)] A subscriber's line L over which normal communication can take place from an instrument NP is associated, when the handset of a second instrument SP is lifted, with secrecy apparatus SE which may be of the kind described in Specification 511,420. To enable a change to be made from normal to secret transmission without releasing the exchange apparatus, cradle springs 2 of the normal instrument are arranged to complete a momentary circuit when the handset is replaced for a relay 8 which bridges the line at 16 and locks up over a thermal switch which unlocks it after a suitable interval. Meanwhile the other handset will have been removed and the line will be bridged in the set SE.
GB1883739A 1939-06-28 1939-06-28 Improvements in and relating to electric communication systems Expired GB531318A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB1883739A GB531318A (en) 1939-06-28 1939-06-28 Improvements in and relating to electric communication systems

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB1883739A GB531318A (en) 1939-06-28 1939-06-28 Improvements in and relating to electric communication systems

Publications (1)

Publication Number Publication Date
GB531318A true GB531318A (en) 1941-01-02

Family

ID=10119250

Family Applications (1)

Application Number Title Priority Date Filing Date
GB1883739A Expired GB531318A (en) 1939-06-28 1939-06-28 Improvements in and relating to electric communication systems

Country Status (1)

Country Link
GB (1) GB531318A (en)

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