Voice API Programming Guide — June 2005 153
Global Tone Detection and Generation, and Cadenced Tone Generation
deviation of each of the two tones minus any overlap (and minus any truncation by the GTD
detection range).
For example:
•Single Tone: 400 Hz (125 Hz deviation) = bandwidth of 275 to 525 Hz, total of 250 Hz.
•Dual Tone: 450 Hz (50 Hz deviation) and 1000 Hz (75 Hz deviation) = bandwidth of 400 to
500 Hz and 925 to 1075 Hz, total of 250 Hz.
•Dual Tone: 450 Hz (100 Hz deviation) and 600 Hz (100 Hz deviation) = bandwidth of 350 to
550 Hz and 500 to 700 Hz; eliminating overlap, total range = 350 to 700 Hz, total of 350 Hz.
Each tone costs, on average, 1 + round up [1/16 * round up (total frequency range /62.5)].
This allows for:
•1 memory block for the actual template
•1/16 portion of a memory block for an index entry
•range/62.5 multiple indexing for speed
In practice, the 1/16 should be added across tones that have frequency overlap, rather than rounded
up for each tone.
Note: The firmware will often use memory more efficiently than described by the guidelines given above.
These guidelines estimate the maximum memory usage for user-defined tones; the actual usage
may be lower.
13.1.10 Guidelines for Creating User-Defined Tones
The following guidelines apply when creating user-defined tones:
Note: The terms “user-defined tones” and “tone templates” are used interchangeably. Each tone template
specifies the characteristics of one user-defined tone.
•The maximum number of user-defined tone templates is based on tone templates that define a
dual tone with a frequency range (bandwidth) of 63 Hz. (The detection range is the difference
between the minimum and maximum defined frequencies for the tone.)
•On DM3 boards, the maximum number of tone templates is about 40.
•On DM3 boards, the number of user-defined tone templates that are active and enabled on a
channel is limited due to the number of events that a channel can report. The default maximum
number of events for a channel is 20. (A tone-on event and a tone-off event in the same tone
template count as two events.)
•On DM3 boards, the default call progress analysis tones (which include tri-tone special
information tone sequences or SIT sequences) are created at board initialization time and are
available for use. If you create new call progress analysis tone templates using
dx_querytone(), dx_deletetone( ) and dx_createtone( ), each tone template counts as a user-
defined tone template, which reduces the number of user-defined tones you can create.
•On Springware boards, if you use call progress analysis to detect the different call progress
signals (dial tone, busy tone, ringback tone, fax or modem tone), call progress analysis creates
GTD tones. This reduces the number of user-defined tones you can create. Call progress