6.5 Energy Detector

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AG boards are capable of running an energy detector which examines the inband signal, distinguishing between silence and energy. The energy detector generates the following events:
ADIEVN_SILENCE_DETECTED ADIEVN_ENERGY_DETECTED ADIEVN_ENERGY_DETECT_DONE
The energy detector functions are:
Function

Description

adiStartEnergyDetector

Starts the energy detector.

adiStopEnergyDetector

Stops the energy detector.
The adiStartEnergyDetector function takes two qualification time parameters:

Energy Qualification Time: The time in milliseconds in which energy must be present to report an energy event.

Silence Qualification Time: The time in milliseconds in which energy must not be present to report a silence event.
Other parameters for the energy detector are defined in a structure with default values. You can modify the energy detector's default behavior by specifying the following parameters when invoking adiStartEnergyDetector:

Threshold Amplitude: The noise level in dBm, below which is considered silence. Noise above this level is further qualified as energy.

Deglitch Time: The minimum time in milliseconds before a transition between energy and silence is recognized.

Automatic Stop: Controls whether the energy detector continues running after the first event. By default, automatic stop is enabled.
Figure 27 illustrates the energy detection parameters.

: Energy Detection Parameters

The above parameter information is communicated via the ADIENERGYDETECT parameter structure whose exact representation is defined in Appendix D of the AG Access Function Reference Manual.
The adiStopEnergyDetector function immediately terminates energy/silence detection. AG Access generates an ADIEVN_ENERGYDETECT_DONE event with the value set to ADI_REASON_STOPPED, meaning stopped short by request.
AG Access may also generate the ADIEVN_ENERGYDETECT_DONE event with an error code, ADIERR_xxx, or with the value set to ADI_REASON_FINISHED. When set to auto-stop (one-shot), the value is set to ADIEVN_REASON_FINISHED and the size field contains either ADIEVN_ENERGY_DETECTED or ADIEVN_SILENCE_DETECTED.

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Copyright 1996 Natural MicroSystems, Inc. All Rights Reserved.