JPS577659A - Extension secret call system of key telephone set - Google Patents

Extension secret call system of key telephone set

Info

Publication number
JPS577659A
JPS577659A JP8085280A JP8085280A JPS577659A JP S577659 A JPS577659 A JP S577659A JP 8085280 A JP8085280 A JP 8085280A JP 8085280 A JP8085280 A JP 8085280A JP S577659 A JPS577659 A JP S577659A
Authority
JP
Japan
Prior art keywords
key telephone
telephone set
extension
calling
turns
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.)
Pending
Application number
JP8085280A
Other languages
Japanese (ja)
Inventor
Gunzo Kita
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.)
Iwatsu Electric Co Ltd
Original Assignee
Iwatsu Electric 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 Iwatsu Electric Co Ltd filed Critical Iwatsu Electric Co Ltd
Priority to JP8085280A priority Critical patent/JPS577659A/en
Publication of JPS577659A publication Critical patent/JPS577659A/en
Pending legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04M—TELEPHONIC COMMUNICATION
    • H04M9/00—Arrangements for interconnection not involving centralised switching
    • H04M9/002—Arrangements for interconnection not involving centralised switching with subscriber controlled access to a line, i.e. key telephone systems
    • H04M9/005—Arrangements for interconnection not involving centralised switching with subscriber controlled access to a line, i.e. key telephone systems with subscriber controlled access to an exchange line

Landscapes

  • Engineering & Computer Science (AREA)
  • Signal Processing (AREA)
  • Sub-Exchange Stations And Push- Button Telephones (AREA)

Abstract

PURPOSE:To eliminate influence of a loop resistance and to detect an answer from a called subscriber securely by providing a control line other than a calling line and by further providing an outflow and an inflow source for currents. CONSTITUTION:The internal calling operation of a key telephone set 1 turns on an SCR1. Consequently, a transistor (TR) Q11 turns on while a TRQ10 turns off, and a contact 1p is still closed, thereby connecting a calling network to extension channels P1 and P2. If a key telephone set (not shown in the figure) is provided at a called extension side, it is connected to the extension channels P1 and P2 as well as the calling operation of the key telephone set 1. Currents flowing through the paths from the key telephone sets 1 and 2 join together on a line P3 to reach -V via TRQn3 and Rn7. The current value of the confluence is nearly equal to that of a constant current In determined by ZDn1 and the Rn7 in a key telephone set (n). Therefore, the 3rd key telephone set, even if intend to interrupt the extension calling, fails.
JP8085280A 1980-06-17 1980-06-17 Extension secret call system of key telephone set Pending JPS577659A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP8085280A JPS577659A (en) 1980-06-17 1980-06-17 Extension secret call system of key telephone set

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP8085280A JPS577659A (en) 1980-06-17 1980-06-17 Extension secret call system of key telephone set

Publications (1)

Publication Number Publication Date
JPS577659A true JPS577659A (en) 1982-01-14

Family

ID=13729870

Family Applications (1)

Application Number Title Priority Date Filing Date
JP8085280A Pending JPS577659A (en) 1980-06-17 1980-06-17 Extension secret call system of key telephone set

Country Status (1)

Country Link
JP (1) JPS577659A (en)

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