CMX673 Просмотр технического описания (PDF) - MX-COM Inc

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CMX673

Call Progress Tone Detector

MX-COM Inc  

Call Progress Tone Detector

3 External Components

Page 5 of 11

CMX673 Preliminary Information

Figure 2: Recommended External Components

C1 Note 1

0.1µF

± 20%

C2

1µF

± 20%

X1 Note 2, 3 3.579545MHz

Table 2: Recommended External Components

Note:

1. C1 is not required if the input is referenced to VREF.

2. Reference Section 6.1

3. For best results, a crystal oscillator design should drive the clock inverter input with signal levels of at least

40% of VDD, peak to peak. Tuning fork crystals generally cannot meet this requirement. To obtain crystal

oscillator design assistance, consult your crystal manufacturer.

4 General Description

4.1 Overall Function Description

The CMX673 Call Progress Tone Detector uses different tone detection methods from those commonly found

with other products.

Many traditional devices use a bandpass filter followed by an energy detector. The filter is usually designed to

pass input signals with a frequency between about 300Hz and 700Hz, and the amplitudes of signals in this

range are then checked against a level threshold. Any signal of acceptable level in this frequency band is

classed as a Call Progress tone, including signals due to speech and noise. False outputs caused by speech

are a common feature with these products, and background noise may lead to a stuck “detect” output.

The CMX673, by contrast, uses a stochastic signal processing technique based on analysis in both the

frequency and time domains, with signal amplitude forming part of the decision process. This analysis

includes checks on whether the signal has a “profile” which matches international standards for Call Progress

tone, or a profile more likely to match that of speech, noise or no signal.

ã2001 MX-COM, Inc

www.mxcom.com Tel: 800 638 5577 336 744 5050 Fax: 336 744 5054

Doc. # 20480182.007

4800 Bethania Station Road, Winston-Salem, NC 27105-1201 USA All Trademarks and service marks are held by their respective companies.

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