JPS55147864A - Change-over controlling circuit of speaker telephone set - Google Patents

Change-over controlling circuit of speaker telephone set

Info

Publication number
JPS55147864A
JPS55147864A JP5546679A JP5546679A JPS55147864A JP S55147864 A JPS55147864 A JP S55147864A JP 5546679 A JP5546679 A JP 5546679A JP 5546679 A JP5546679 A JP 5546679A JP S55147864 A JPS55147864 A JP S55147864A
Authority
JP
Japan
Prior art keywords
transmission
signal
change
multivibrators
receiving
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
JP5546679A
Other languages
Japanese (ja)
Inventor
Hisashi Fujisaki
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.)
NEC Corp
Original Assignee
NEC Corp
Nippon 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 NEC Corp, Nippon Electric Co Ltd filed Critical NEC Corp
Priority to JP5546679A priority Critical patent/JPS55147864A/en
Publication of JPS55147864A publication Critical patent/JPS55147864A/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
    • H04M9/08—Two-way loud-speaking telephone systems with means for conditioning the signal, e.g. for suppressing echoes for one or both directions of traffic

Landscapes

  • Engineering & Computer Science (AREA)
  • Signal Processing (AREA)

Abstract

PURPOSE:To eliminate malfunctions to facilitate interrupt of transmission and receiving, by constituting a digital switching control circuit by hysteresis comparators, multivibrators and an FF. CONSTITUTION:The signal input from transmission channel and receiving channel power detection terminals 21T and 21R is applied to hysteresis comparators 22T and 22R to detect the sound signal, and this signal is converted to a pulse train, and retrigger monostable multivibrators 23T and 23R are driven by this output pulse train. Outputs of monostable multivibrators 23T and 23R are connected to not only set and reset inputs of RSFF 24 respectively but also reset inputs of the retrigger monostable multivibrator of each other. Then, the variable attenuator of transmission and receiving channels is controlled by output signal 25 of RSFF 24.
JP5546679A 1979-05-07 1979-05-07 Change-over controlling circuit of speaker telephone set Pending JPS55147864A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP5546679A JPS55147864A (en) 1979-05-07 1979-05-07 Change-over controlling circuit of speaker telephone set

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP5546679A JPS55147864A (en) 1979-05-07 1979-05-07 Change-over controlling circuit of speaker telephone set

Publications (1)

Publication Number Publication Date
JPS55147864A true JPS55147864A (en) 1980-11-18

Family

ID=12999375

Family Applications (1)

Application Number Title Priority Date Filing Date
JP5546679A Pending JPS55147864A (en) 1979-05-07 1979-05-07 Change-over controlling circuit of speaker telephone set

Country Status (1)

Country Link
JP (1) JPS55147864A (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS57173250A (en) * 1981-04-17 1982-10-25 Hitachi Ltd Voice switch circuit
JPH01253353A (en) * 1988-03-31 1989-10-09 Fujitsu Ten Ltd Howling canceler system for hand-free telephone

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS57173250A (en) * 1981-04-17 1982-10-25 Hitachi Ltd Voice switch circuit
JPH01253353A (en) * 1988-03-31 1989-10-09 Fujitsu Ten Ltd Howling canceler system for hand-free telephone

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