JPS61146058A - Conference telephone system - Google Patents

Conference telephone system

Info

Publication number
JPS61146058A
JPS61146058A JP26928084A JP26928084A JPS61146058A JP S61146058 A JPS61146058 A JP S61146058A JP 26928084 A JP26928084 A JP 26928084A JP 26928084 A JP26928084 A JP 26928084A JP S61146058 A JPS61146058 A JP S61146058A
Authority
JP
Japan
Prior art keywords
party
band noise
telephone system
noise
band
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
JP26928084A
Inventor
Tatsu Nakahara
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 JP26928084A priority Critical patent/JPS61146058A/en
Publication of JPS61146058A publication Critical patent/JPS61146058A/en
Pending legal-status Critical Current

Links

Classifications

    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04MTELEPHONIC COMMUNICATION
    • H04M9/00Interconnection arrangements not involving centralised switching
    • H04M9/08Two-way loud-speaking telephone systems with means for suppressing echoes or otherwise conditioning for one or other direction of traffic
    • H04M9/085Two-way loud-speaking telephone systems with means for suppressing echoes or otherwise conditioning for one or other direction of traffic using digital techniques
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04MTELEPHONIC COMMUNICATION
    • H04M3/00Automatic or semi-automatic exchanges
    • H04M3/42Systems providing special services or facilities to subscribers
    • H04M3/56Arrangements for connecting several subscribers to a common circuit, i.e. affording conference facilities

Abstract

PURPOSE:To prevent an in-band noise for measuring a side tone coupling loss quantity, from brought to loudspeaking in the own conference room by obstructing the passing of a signal of a receiving channel, when a level ratio of a frequency component of an in-band noise from a conference telephone system of the other party is a prescribed party. CONSTITUTION:When a measurement of a side tone coupling loss is executed in a conference room of the other party side, an in-band noise for a measurement use is inputted to an A/D converting circuit 6 and a filter circuit 14 through a two-wire/four-wire converting circuit 8 from a conference telephone system of the other party. This noise is an in-band noise containing all spectrums of a transmission frequency band, therefore, signal levels of a low frequency and a high frequency from the filter circuit 14 become almost the same level. Accordingly, in a controlling circuit 7, levels of these two frequencies are compared, and in case when both the frequencies have become almost the same level, a receiving channel switch 15 is detached, and this in-band noise is prevented from being outputted from a loudspeaker 10.
JP26928084A 1984-12-20 1984-12-20 Conference telephone system Pending JPS61146058A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP26928084A JPS61146058A (en) 1984-12-20 1984-12-20 Conference telephone system

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP26928084A JPS61146058A (en) 1984-12-20 1984-12-20 Conference telephone system

Publications (1)

Publication Number Publication Date
JPS61146058A true JPS61146058A (en) 1986-07-03

Family

ID=17470153

Family Applications (1)

Application Number Title Priority Date Filing Date
JP26928084A Pending JPS61146058A (en) 1984-12-20 1984-12-20 Conference telephone system

Country Status (1)

Country Link
JP (1) JPS61146058A (en)

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS56136071A (en) * 1980-03-26 1981-10-23 Toshiba Corp Side-tone preventing circuit
JPS5792926A (en) * 1980-11-29 1982-06-09 Toshiba Corp Echo cancelling device
JPS59193660A (en) * 1983-04-18 1984-11-02 Nec Corp Conference telephone set

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS56136071A (en) * 1980-03-26 1981-10-23 Toshiba Corp Side-tone preventing circuit
JPS5792926A (en) * 1980-11-29 1982-06-09 Toshiba Corp Echo cancelling device
JPS59193660A (en) * 1983-04-18 1984-11-02 Nec Corp Conference telephone set

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