JPS5675792A - Reception system for multifrequency signal - Google Patents

Reception system for multifrequency signal

Info

Publication number
JPS5675792A
JPS5675792A JP15210479A JP15210479A JPS5675792A JP S5675792 A JPS5675792 A JP S5675792A JP 15210479 A JP15210479 A JP 15210479A JP 15210479 A JP15210479 A JP 15210479A JP S5675792 A JPS5675792 A JP S5675792A
Authority
JP
Japan
Prior art keywords
threshold value
circuit
signal
detection
level
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.)
Granted
Application number
JP15210479A
Other languages
Japanese (ja)
Other versions
JPS592233B2 (en
Inventor
Ryujiro Muramatsu
Kazuto Hirose
Yasumasa Iwase
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.)
Hitachi Ltd
Nippon Telegraph and Telephone Corp
Original Assignee
Hitachi Ltd
Nippon Telegraph and Telephone 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 Hitachi Ltd, Nippon Telegraph and Telephone Corp filed Critical Hitachi Ltd
Priority to JP54152104A priority Critical patent/JPS592233B2/en
Publication of JPS5675792A publication Critical patent/JPS5675792A/en
Publication of JPS592233B2 publication Critical patent/JPS592233B2/en
Expired legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q1/00—Details of selecting apparatus or arrangements
    • H04Q1/18—Electrical details
    • H04Q1/30—Signalling arrangements; Manipulation of signalling currents
    • H04Q1/44—Signalling arrangements; Manipulation of signalling currents using alternate current
    • H04Q1/444—Signalling arrangements; Manipulation of signalling currents using alternate current with voice-band signalling frequencies
    • H04Q1/45—Signalling arrangements; Manipulation of signalling currents using alternate current with voice-band signalling frequencies using multi-frequency signalling
    • H04Q1/457—Signalling arrangements; Manipulation of signalling currents using alternate current with voice-band signalling frequencies using multi-frequency signalling with conversion of multifrequency signals into digital signals
    • H04Q1/4575—Signalling arrangements; Manipulation of signalling currents using alternate current with voice-band signalling frequencies using multi-frequency signalling with conversion of multifrequency signals into digital signals which are transmitted in digital form

Landscapes

  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Digital Transmission Methods That Use Modulated Carrier Waves (AREA)

Abstract

PURPOSE:To increase the protective characteristics for momentary interruption, by performing signal detection with the fixed threshold value of comparatively high level, then switching the threshold value after detection to the value of low level performing the signal detection afterward. CONSTITUTION:A multifrequency signal input is converted into a linear PCM code and fed to an adder 16 after being frequency spectral. In this case, since the preceding input signal is absent, the first fixed threshold value of a selection circuit 15 is selected and the 1st threshold value is fed to the adder 16 from a threshold value generating circuit 13. Then, the output level of a discrete Fourier transformation operating circuit 12 is compared with the 1st fixed threshold value for signal detection. Next, from the result of detection, the selector circuit 15 is switched to select the second fixed threshold value lower in the level than the 1st threshold value. After that, the output of the circuit 12 is compared with the 2nd threshold value to detect the signal. If momentary interruption is caused, when the time width of the monentary interruption is within a permissible range, the output level of the circuit 12 is not lowered than the 2nd threshold value.
JP54152104A 1979-11-26 1979-11-26 Multi-frequency signal reception method Expired JPS592233B2 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP54152104A JPS592233B2 (en) 1979-11-26 1979-11-26 Multi-frequency signal reception method

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP54152104A JPS592233B2 (en) 1979-11-26 1979-11-26 Multi-frequency signal reception method

Publications (2)

Publication Number Publication Date
JPS5675792A true JPS5675792A (en) 1981-06-23
JPS592233B2 JPS592233B2 (en) 1984-01-17

Family

ID=15533134

Family Applications (1)

Application Number Title Priority Date Filing Date
JP54152104A Expired JPS592233B2 (en) 1979-11-26 1979-11-26 Multi-frequency signal reception method

Country Status (1)

Country Link
JP (1) JPS592233B2 (en)

Also Published As

Publication number Publication date
JPS592233B2 (en) 1984-01-17

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