The following table lists the input frequencies supported by default, along with their corresponding identifiers (that may be used in calls to sm_add_input_tone_set().
| Id | Lower Freq rejection coefficient | Upper Freq rejection coefficient | Description |
|---|---|---|---|
| 0 | 679.6875 | 710.9375 | DTMF frequency 1 |
| 1 | 742.1875 | 789.0625 | DTMF frequency 2 |
| 2 | 835.9375 | 867.1875 | DTMF frequency 3 |
| 3 | 914.0625 | 960.9375 | DTMF frequency 4 |
| 4 | 1179.6875 | 1242.1875 | DTMF frequency 5 |
| 5 | 1304.6875 | 1367.1875 | DTMF frequency 6 |
| 6 | 1445.3125 | 1507.8125 | DTMF frequency 7 |
| 7 | 1601.5625 | 1664.0625 | DTMF frequency 8 |
| 8 | 304.6875 | 554.6875 | Call Progress 1 |
| 9 | 898.4375 | 1007.8125 | Call Progress 2 |
| 10 | 1335.9375 | 1460.9375 | Call Progress 3 |
| 11 | 1742.1875 | 1851.5625 | Call Progress 4 |
| 12 | 589.0 | 651.0 | Call Progress 5 |
| 13 | 1062.0 | 1138.0 | Fax CNG |
| 14 | 2085.0 | 2115.0 | Fax CED |
The following table lists the sets of simple (single or dual component frequency) input tones that may be selected as the set of tones to listen for on an input channel that are supported by default and the corresponding identifiers for the sets (that may be used in calls to sm_listen_for()). Additional tone sets may be defined by an application through calls to sm_add_input_tone_set()
| Id | ||
|---|---|---|
| 0 | 1 | |
| Description of tone set | DTMF | Call progress & fax |
| Band 1 first frequency coeff id | 0 | * see note below |
| Band 1 frequency count | 4 | * see note below |
| Band 2 first frequency coeff id | 4 | * see note below |
| Band 2 frequency count | 4 | * see note below |
| Required third peak ratio | 0.079432823 | 0.1 |
| Required signal to noise ratio | 0.755573455 | 0.5 |
| Required minimum power | -36 | -36 |
| Twist ratio for dual tone | 10 | 0 |
| Start of frequency range (Hz) | 250 | 250 |
| End of frequency range (Hz) | 3406 | 3406 |
* Note about pre-loaded input tone set for call progress and fax
A specially constucted set of component frequency pairs is used for the preloaded toneset 1 for call progress and fax tones. It is constructed from the 7 preloaded input frequencies with ids from 8 to 14. Normally (i.e. for tonesets added through the API) all combinations of the specified two frequency bands are included in the set of tones to listen for. With the special preloaded toneset 1 the combinations are restricted to a subset being the individual single tones and the addition of two dual tones. This accomodates the use of the toneset by the cadenced call progress tone detector to detect a range of different busy and dial tones.
The enumeration of specially constructed set of frequency pairs is given in this table. Note if this toneset used for tone detection rather than call-progress tone detection, silence is omitted from the enumeration and the values returned by sm_get_recognised() would be the value in the table minus one, so for example fax CED would be 8.