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Subject: CMX673: Suggested Applications
The CMX673 is an 8-pin DIP or 16-pin SOIC signal-detector that operates on energy in the frequency band of
about 315 to 650 Hz. Its primary use is in the detection of status tones encountered during the progression of
a telephone call.
These tones include: dial tone, circuits busy, ring tone, station busy and others. Call status is derived by
examining the cadence of those tones.
[application note link].