JPS6430395A - Key telephone system - Google Patents

Key telephone system

Info

Publication number
JPS6430395A
JPS6430395A JP18818587A JP18818587A JPS6430395A JP S6430395 A JPS6430395 A JP S6430395A JP 18818587 A JP18818587 A JP 18818587A JP 18818587 A JP18818587 A JP 18818587A JP S6430395 A JPS6430395 A JP S6430395A
Authority
JP
Japan
Prior art keywords
waveform
resistor
detecting
telephone set
circuit
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
JP18818587A
Other languages
Japanese (ja)
Inventor
Toshikazu Suzuki
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
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 filed Critical NEC Corp
Priority to JP18818587A priority Critical patent/JPS6430395A/en
Publication of JPS6430395A publication Critical patent/JPS6430395A/en
Pending legal-status Critical Current

Links

Landscapes

  • Sub-Exchange Stations And Push- Button Telephones (AREA)

Abstract

PURPOSE:To enable a resistor for hook-off detection and a capacitor connected in parallel with this resistor to be small and to miniaturize a circuit by monitoring the waveform of the voltage across the hook-off detecting resistor, and detecting and hooking-off of the telephone set at a time when said waveform is changed. CONSTITUTION:A main equipment 1 is provided with an independent telephone interface part 2 and a call signal generation part 3 to generate a call signal in rectangle waveform. And the part 2 is provided with the resistor 6 to detect the hooking-off of the single dent telephone set 4, and a voltage waveform detection circuit 5 monitors the change of the voltage waveform across the resistor 6 from the differential waveform of a square waveform to another rectangle waveform when the telephone set 4 is hooked off during the transmission of a call signal from the generation part 3 to the telephone set 4. By monitoring the voltage waveform across the hook-off detecting resistor 6, and detecting a hooking-off as said in the above, no large-capacity capacitor is necessary to be used in a ring trip circuit 5, and the circuit can be miniaturized.
JP18818587A 1987-07-27 1987-07-27 Key telephone system Pending JPS6430395A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP18818587A JPS6430395A (en) 1987-07-27 1987-07-27 Key telephone system

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP18818587A JPS6430395A (en) 1987-07-27 1987-07-27 Key telephone system

Publications (1)

Publication Number Publication Date
JPS6430395A true JPS6430395A (en) 1989-02-01

Family

ID=16219254

Family Applications (1)

Application Number Title Priority Date Filing Date
JP18818587A Pending JPS6430395A (en) 1987-07-27 1987-07-27 Key telephone system

Country Status (1)

Country Link
JP (1) JPS6430395A (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5311464A (en) * 1990-06-08 1994-05-10 Kabushiki Kaisha Toshiba Semiconductor memory cell farming a ROM cell from a RAM cell

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5311464A (en) * 1990-06-08 1994-05-10 Kabushiki Kaisha Toshiba Semiconductor memory cell farming a ROM cell from a RAM cell

Similar Documents

Publication Publication Date Title
EP0387837A3 (en) Externally discernible power supply abnormality detection system
EP0310433A3 (en) Radio telephone device
TW265500B (en)
US5668870A (en) Audible signaling device for informing when a telephone line is available or in use
JPS6430395A (en) Key telephone system
JPS5471347A (en) State detector
JPS5523551A (en) Control unit diagnostic equipment
JPS6469143A (en) Facsimile equipment
ES8705729A1 (en) Interswitch line circuit.
JPS57145466A (en) Switchboard
JPS6446820A (en) Interface switching system
JPS6439869A (en) Network control unit
JPS5476098A (en) Normal monitor system for open wire
JPS6429052A (en) Line switcher
JPS644152A (en) Cpu controlled type subscriber line control interface circuit
JPS5593070A (en) Frequency decision circuit
JPS6416169A (en) Telephone set with call charge display function
JPS5793795A (en) Electronic signal controller
JPS648752A (en) Signal detection circuit for telephone set
JPS5228298A (en) Supervisory alarm unit by loop circuit system
KR100264033B1 (en) Interface device of network connection unit using a telephone line
JPS55123734A (en) Mode display unit of electronic desk calculator
JPS55113959A (en) Apparatus for measuring power flow
MY105674A (en) Apparatus for detecting the configuration of a communication port.
JPS6478041A (en) Radio telephone set