- 您現(xiàn)在的位置：買賣IC網(wǎng) > PDF目錄383641 > MT8870 (Mitel Networks Corporation) () PDF資料下載
參數(shù)資料
| 型號： | MT8870 |
| 廠商： | Mitel Networks Corporation |
| 英文描述： | () |
| 中文描述： | （） |
| 文件頁數(shù)： | 1/23頁 |
| 文件大小： | 177K |
| 代理商： | MT8870 |
A-45
Contents
DTMF Receiver Development
Mobile Radio Applications
Inside The MT8870
Distributed Control Systems
DTMF Receiver Application
Data Communication Using DTMF
Introduction
The purpose of this Application Note is to provide
information on the operation and application of
DTMF Receivers. The MT8870 Integrated DTMF
Receiver will be discussed in detail and its use
illustrated in the application examples which follow.
More than 25 years ago the need for an improved
method for transferring dialling information through
the telephone network was recognized. The
traditional method, Dial pulse signalling, was not only
slow, suffering severe distortion over long wire loops,
but required a DC path through the communications
channel. A signalling scheme was developed
utilizing voice frequency tones and implemented as a
very reliable alternative to pulse dialling. This
scheme is known as DTMF (Dual Tone Multi-
Frequency), Touch-Tone
or simply, tone dialling.
As its acronym suggests, a valid DTMF signal is the
sum of two tones, one from a low group (697-941Hz)
and one from a high group (1209-1633Hz) with each
group containing four individual tones. The tone
frequencies were carefully chosen such that they are
not
harmonically
related
intermodulation products result in minimal signalling
impairment (Fig. 1a). This scheme allows for 16
unique combinations. Ten of these codes represent
the numerals zero through nine, the remaining six
(*,#,A,B,C,D) being reserved for special signalling.
Most telephone keypads contain ten numeric push
buttons plus the asterisk (*) and octothorp (#). The
buttons are arranged in a matrix, each selecting its
low group tone from its respective row and its high
group tone from its respective column (Fig. 1b).
and
that
their
The DTMF coding scheme ensures that each signal
contains one and only one component from each of
the high and low groups. This significantly simplifies
decoding because the composite DTMF signal may
be separated with bandpass filters, into its two single
frequency components each of which may be
handled individually. As a result DTMF coding has
proven to provide a flexible signalling scheme of
excellent reliability, hence motivating innovative and
competitive decoder design.
Development
Early DTMF decoders (receivers) utilized banks of
bandpass
filters
making
cumbersome and expensive to implement. This
generally restricted their application to central offices
(telephone exchanges).
them
somewhat
The first generation receiver typically used LC filters,
active filters and/or phase locked loop techniques to
Figure 1a - The Dual Tone Multifrequency (DTMF) Spectrum
685 709
756 784
837 867
925 957
1189
1358
1501
1659
1229
1314
1453
1607
697
770
852
941
1209
1336
1477
1633
2 dB
Tones generated from a telephone typically have -2 dB twist
(pre-emphasis) applied to compensate for high frequency
roll off along the telephone line.
AMPLITUDE
f (Hz)
logarithmic
Standard DTMF frequency spectrum
±
(1.5% + 2 Hz). Second harmonics of the low group (possibly
created due to a non-linear channel) fall within the passband of the high group (Indicated by A,B,C,D).
This is a potential source of interference.
A
B
C
D
ISSUE 1
June 1983
MSAN-108
Applications of The MT8870
Integrated DTMF Receiver
Application Note
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| MT8880C | ISO2-CMOS Integrated DTMFTransceiver |
| MT8880CE-1 | ISO2-CMOS Integrated DTMFTransceiver |
| MT8880CC | ISO2-CMOS Integrated DTMFTransceiver |
| MT8880CE | ISO2-CMOS Integrated DTMFTransceiver |
| MT8880CN | ISO2-CMOS Integrated DTMFTransceiver |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MT8870BE | 制造商:Panasonic Industrial Company 功能描述:RECEIVER |
| MT8870D | 制造商:MITEL 制造商全稱:Mitel Networks Corporation 功能描述:ISO2-CMOS Integrated DTMF Receiver |
| MT8870DC | 制造商:MITEL 制造商全稱:Mitel Networks Corporation 功能描述:ISO2-CMOS Integrated DTMF Receiver |
| MT8870DC-1 | 制造商:MITEL 制造商全稱:Mitel Networks Corporation 功能描述:ISO2-CMOS Integrated DTMF Receiver |
| MT8870DE | 制造商:Microsemi Corporation 功能描述: |
發(fā)布緊急采購，3分鐘左右您將得到回復(fù)。