Title:
TONE RECEIVER
Document Type and Number:
Japanese Patent JPS598455
Kind Code:
A
Abstract:
A device for detecting the presence of an alarm tone of a given frequency within a received signal carrying digital data in addition to said tone. The receiver comprises an analog-to-digital converter (42) the output of which is applied to a first recursive bandpass filter centered at the frequency of the alarm tone and the feedback loop of which includes a limiter. In addition, an input feedforward loop is provided for adding (at 58) the output signal from the converter (42), as multiplied by a coefficient gamma , to the output signal from the limiter. The output signal from the adder (58) is hard limited (at 44), then passed through a second bandpass filter. The energy of the signal obtained at the output of said second filter is then measured to provide indication of a tone's being received when said energy exceeds a predetermined threshold.
Inventors:
DOMINIKU GODAARU
Application Number:
JP6464483A
Publication Date:
January 17, 1984
Filing Date:
April 14, 1983
Export Citation:
Assignee:
IBM
International Classes:
H04L12/26; H04L27/00; E04H9/00; H04L29/00; H04Q1/448; (IPC1-7): H04L13/00; H04L27/00
Domestic Patent References:
| JPS50113102A | 1975-09-05 |
Attorney, Agent or Firm:
Koichi Tonmiya
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