JPS6486747A - Door phone circuit - Google Patents

Door phone circuit

Info

Publication number
JPS6486747A
JPS6486747A JP24463487A JP24463487A JPS6486747A JP S6486747 A JPS6486747 A JP S6486747A JP 24463487 A JP24463487 A JP 24463487A JP 24463487 A JP24463487 A JP 24463487A JP S6486747 A JPS6486747 A JP S6486747A
Authority
JP
Japan
Prior art keywords
door phone
current detection
attenuator
resistor
constitution
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
JP24463487A
Other languages
Japanese (ja)
Inventor
Mitsuhiro Matsuda
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.)
Toshiba Electric Equipment Corp
Original Assignee
Toshiba Electric Equipment Corp
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 Toshiba Electric Equipment Corp filed Critical Toshiba Electric Equipment Corp
Priority to JP24463487A priority Critical patent/JPS6486747A/en
Publication of JPS6486747A publication Critical patent/JPS6486747A/en
Pending legal-status Critical Current

Links

Landscapes

  • Interconnected Communication Systems, Intercoms, And Interphones (AREA)

Abstract

PURPOSE:To easily realize individual call constitution from two places by providing an attenuator which reduces the gain of a transmission system when a detected current by a door phone line current detection circuit exceeds an ordinary speech current. CONSTITUTION:The attenuator 12 is constituted by utilizing the saturation of a transistor Tr connected between the output terminals of a feed line and a microphone 2, and the door phone line current detection circuit 11 is constituted so that current detection can be performed by the base-emitter voltage VBE of the transistor Tr based on the voltages at both ends of a resistor R3 connected in series between a resistor R4 and the feed line. A remarkably simple wiring system can be realized only by performing the branch connection of a door phone 7 and an additional call switch 10 to a door phone line 8, and the individual call from the two places can be realized without restricting other performance.
JP24463487A 1987-09-29 1987-09-29 Door phone circuit Pending JPS6486747A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP24463487A JPS6486747A (en) 1987-09-29 1987-09-29 Door phone circuit

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP24463487A JPS6486747A (en) 1987-09-29 1987-09-29 Door phone circuit

Publications (1)

Publication Number Publication Date
JPS6486747A true JPS6486747A (en) 1989-03-31

Family

ID=17121671

Family Applications (1)

Application Number Title Priority Date Filing Date
JP24463487A Pending JPS6486747A (en) 1987-09-29 1987-09-29 Door phone circuit

Country Status (1)

Country Link
JP (1) JPS6486747A (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102004022438B3 (en) * 2004-05-06 2005-12-29 Frey, Ernst Turn signal display driving device for vehicles

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102004022438B3 (en) * 2004-05-06 2005-12-29 Frey, Ernst Turn signal display driving device for vehicles

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