6.6 Tone Detectors

The tone detector runs a precise tone filter for a single or dual frequency tone. Each AG Access port has up to three programmable tone detectors. If the port is running a protocol employing an inband cleardown tone, the first tone detector is consumed by AG Access. The following events are generated by the tone detectors:

ADIEVN_TONE_n_BEGIN Where n is the programmable tone ID (1-3)
ADIEVN_TONE_n_END Where n is the programmable tone ID (1-3)

The tone detector functions are:

Function	Description
adiStartToneDetector	Starts a tone detector.
adiStopToneDetector	Stops a tone detector.

In addition to the tone detector identifier which specifies a tone ID of 1-3, the adiStartToneDetector function takes four parameters that describe a single or dual frequency tone:

• Frequency 1: The center frequency in Hz of a single tone or the first of two frequencies in a dual tone.

• Bandwidth 1: The bandwidth around Frequency 1 that is considered acceptable.

• Frequency 2: The center frequency in Hz of the second of two frequencies in a dual tone. This value should be set to zero for single frequency tones.

• Bandwidth 2: The bandwidth around Frequency 2 that is considered acceptable. This value should be set to zero for single frequency tones.

Note that the range of frequencies detected will be the center frequency plus/minus one-half of the bandwidth. Figure 28 illustrates these parameters.

Other parameters for the tone detector are defined in a structure with default values. You can modify the tone detector's default behavior by specifying the following parameters when invoking adiStartToneDetector.

• Qualification Amplitude: The broadband qualification level in dBm required to further qualify any energy as tone.

• Qualification Time: The time in milliseconds in which the tone must be present before reporting ADIEVN_TONE_n_BEGIN. After qualifying at tone, this parameter is used to qualify the absence of the tone to report ADIEVN_TONE_n_END.

Figure 29 illustrates the tone detection qualification parameters.

This parameter information is communicated via the ADITONEDETECT parameter structure whose exact representation is defined in Appendix D of the AG Access Function Reference Manual.

The remaining parameters in the structure (reflevel and reserved) should not be modified. These are parameters to the DSP algorithms and are included in the structure in the case of a field problem for which an NMS engineer may request modification.

The adiStopToneDetector function immediately terminates a tone detector. AG Access generates an ADIEVN_TONEDETECT_DONE event with the value set to ADI_REASON_STOPPED.

AG Access may also generate the ADIEVN_DTMFDETECT_DONE event with an error code, ADIERR_xxx, if the function is started incorrectly.

Copyright 1996 Natural MicroSystems, Inc. All Rights Reserved.