Title:
DTMF TRANSMISSION/RECEPTION CIRCUIT
Document Type and Number:
Japanese Patent JP2819920
Kind Code:
B2
Abstract:
PURPOSE: To drastically improve the output signal quality by incorporating all of required filters without considerably enlarging the circuit scale of a DTMF transmission/reception circuit made of an integrated circuit and reducing the unnecessary sent signal level of the output.
CONSTITUTION: The DTMF transmission/reception circuit is provided with DTMF signal modulating/demodulating circuit 26 and 4, a band-pass filter 22 which separates a low group frequency component of a DTMF signal at the time of receiving the DTMF signal, a low-pass filter 16 which separates a high group frequency component of the DTMF signal, and a high-pass filter 11, and the DTMF signal is transmitted through the low-pass filter 16 at the time of transmitting the DTMF signal, and filters used for transmission/reception are partially shared.
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Inventors:
Shinohara Sachiko
Application Number:
JP2984992A
Publication Date:
November 05, 1998
Filing Date:
February 18, 1992
Export Citation:
Assignee:
NEC
International Classes:
H04L27/26; H04Q1/45; (IPC1-7): H04Q1/45
Attorney, Agent or Firm:
Naoki Kyomoto (2 outside)