JPS56141655A - Call current supply circuit - Google Patents

Call current supply circuit

Info

Publication number
JPS56141655A
JPS56141655A JP4432480A JP4432480A JPS56141655A JP S56141655 A JPS56141655 A JP S56141655A JP 4432480 A JP4432480 A JP 4432480A JP 4432480 A JP4432480 A JP 4432480A JP S56141655 A JPS56141655 A JP S56141655A
Authority
JP
Japan
Prior art keywords
terminal
supply circuit
transistor
current supply
voltage
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
JP4432480A
Other languages
Japanese (ja)
Inventor
Kanji Mukai
Shogo Usuda
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
Nippon Telegraph and Telephone Corp
Original Assignee
NEC Corp
Nippon Telegraph and Telephone 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 Telegraph and Telephone Corp, Nippon Electric Co Ltd filed Critical NEC Corp
Priority to JP4432480A priority Critical patent/JPS56141655A/en
Publication of JPS56141655A publication Critical patent/JPS56141655A/en
Pending legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04M—TELEPHONIC COMMUNICATION
    • H04M19/00—Current supply arrangements for telephone systems
    • H04M19/02—Current supply arrangements for telephone systems providing ringing current or supervisory tones, e.g. dialling tone or busy tone

Landscapes

  • Engineering & Computer Science (AREA)
  • Signal Processing (AREA)
  • Devices For Supply Of Signal Current (AREA)
  • Cable Transmission Systems, Equalization Of Radio And Reduction Of Echo (AREA)

Abstract

PURPOSE:To reduce a call current and protect a call current supply circuit from an excess current, by increasing a DC impedance of the call current supply circuit, in case when abnormal overvoltage is genersted in a telephone line. CONSTITUTION:The terminals 1, 2 are connected to one pair of telephone circuits, and the terminals 3, 4 are connected to the electric power source. For instance, in the event of ground-fault of the terminal 2, the voltage between the terminal 2 and 4 rises abnormally, by which the transistor 20 conducts. As a result, the voltage between the noninversion input terminal of the optional amplifier 18 and the terminal 4 becomes small enough comparing with the voltage between the noninversion input terminal of the operational amplifier 18 and the terminal 2, therefore, the DC impedance between the terminal 2 and 4 incereases, and a current flowing into the first transistor 12 and the resistor 14 can be reduced. The circuit between the terminal 1 and 3 is operated in the same way, ane the first transistor 11 and the resistor 13 are protected.
JP4432480A 1980-04-04 1980-04-04 Call current supply circuit Pending JPS56141655A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP4432480A JPS56141655A (en) 1980-04-04 1980-04-04 Call current supply circuit

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP4432480A JPS56141655A (en) 1980-04-04 1980-04-04 Call current supply circuit

Publications (1)

Publication Number Publication Date
JPS56141655A true JPS56141655A (en) 1981-11-05

Family

ID=12688309

Family Applications (1)

Application Number Title Priority Date Filing Date
JP4432480A Pending JPS56141655A (en) 1980-04-04 1980-04-04 Call current supply circuit

Country Status (1)

Country Link
JP (1) JPS56141655A (en)

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS53138209A (en) * 1977-05-09 1978-12-02 Hitachi Ltd Protective system of trunk circuit

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS53138209A (en) * 1977-05-09 1978-12-02 Hitachi Ltd Protective system of trunk circuit

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