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Subject: FX631 Security and Telephone SPM Detector

This Application Note describes how two FX631 Low-Voltage (Subscriber Pulse Metering) SPM Detector microcircuits can be used, with additional external filter components, to detect both the 12kHz SPM and the 18kHz security tones employed in the French payphone/cardphone system.
[application note link].

Publication: Nil.

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Subject: FX631 FX631xxX clocking information

An Application Note to describe the various Xtal/clock set-ups available to these products.
[application note link].

Publication: AN/Telecom/631X/1 October 1997.

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Subject: CMX631A/FX631 External Component Calculation - A Worked Example

Worked calculations to enable selection of the correct component values to obtain required 'must' and 'must-not' decode frequencies when using these products.
[application note link].

Publication: AN/Telecom/631A/1 June 1999.

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Other Relevant Application Notes

• CML On-chip Oscillators - Configuration Information - [application note link]
• Switched Capacitor Interfacing: Anti-aliasing and Smoothing Filters - [application note link]