CMX673

CMX673 Call Progress Tone Detector D/673/5 June 2001 Provisional Issue Features Worldwide Tone Compatibility Single and Dual Tones Detected Wide Dynamic Signal Range Fast Response Time Low Power Operation 500µA at 3.0V 3.58MHz Xtal/Clock Oscillator Applications Worldwide Payphone Systems Telephone Redialling Systems Dialling Modems Banking and Billing Systems Telecom Test Equipment Telecom Security Systems 1.1 Brief Description The CMX673 is a general purpose call progress tone detector for use in Public Switched Telephone System (PSTN) applications. Call progress detection allows equipment which dials into the PSTN network to monitor the progress of the resulting call. Ringing, Busy, Not available and Answer states can be determined. The CMX673 uses advanced digital signal processing techniques to detect tones in the frequency band 315Hz to 650Hz. The use of DSP techniques allows the CMX673 to distinguish between valid call progress tone signals and line noise or voice, low false detection rates result. This is in contrast to other call progress detection devices which are based on simple filtering techniques. The detection timing of the CMX673 allows it to operate with almost any call progress system. In particular the ‘stuttered dial tone’ of voice mail messaging systems is supported. The use of digital processing and small geometry CMOS design techniques allows the CMX673 to offer a complete call progress detector which analyses both frequency a...