How call progress tones are defined

Each tone is defined by the following parameters:

Tone Type
Tone Label
Frequency (up to three frequency components can be specified)
Level (of up to three frequency components)
Cadence (of up to three frequency components)

Tone Type

The call progress tones and the tone types vary from country to country. However, four basic types, in addition to "voice activity detection", exist in all countries. They are:

Ring

An audible ringing tone.

Dial tone

An audible dialing tone.

Busy

An audible line busy (engaged) tone.

Network Busy

A tone that is generated when all central office circuits are in use. Also known as equipment busy.

Other

The availability of other call progress tones in a specific country or region is dependent upon the telephone system of that country or region.

Note: Some of these tones are not already defined to Blueworx Voice Response. To enable Blueworx Voice Response to use these, you must follow the procedure described in Redefining call progress tones.

The tone type is specified by the Tone Type parameter in the call progress tone definition.

Tone Label

The tone label is a description of the tone that you specify by using the Tone Label parameter in the call progress tone definition.

Frequency

The frequencies are defined in Hertz (Hz). Up to three frequencies can be defined for each tone. A Frequency Maximum and a Frequency Minimum parameter value for each frequency component defines the qualifying range.
The minimum value for tone frequencies is nominal frequency - 9% and the maximum value for tone frequencies is nominal frequency +9%.

Double interrupted tones, for example, 400 ms on, 200 ms off, 400 ms on, 2000 ms off, must be split into two parts. For an example of how to do this, see Ring Part 1 Tone and Ring Part 2 Tone in the tone parameter table for the United Kingdom.

Level

The levels are defined in decibels (dBm). A Level Maximum and a Level Minimum parameter value for each frequency component defines the qualifying range.
The minimum level for each tone is set to 6 dBm lower than the expected minimum value. Set the maximum level to 0 dBm.

Cadence

The cadences are defined in terms of Time On and Time Off. A Time On Maximum and a Time On Minimum parameter value for each frequency component defines how long a signal of the specified frequency and level must be to qualify as a valid component of the tone. A Time Off Maximum and a Time Off Minimum parameter value for each frequency component defines how long a period must elapse between signals. No Time parameters are specified for a continuous tone.
The values for times are set in 20 ms increments, rounded to the next lowest for minimum value and to the next highest for maximum value. The minimum value for a tone cadence is specified as nominal time (on or off) -15% and the maximum value for a tone cadence is specified as nominal time (on or off) +15%.

Example: How to work out maximum and minimum values from nominal values

To define a dual tone specified by the nominal values shown in Table 1, perform the calculations shown in Example call progress tone calculations to work out the maximum and minimum values:

Table 1. Example call progress tone nominal values.
This table describes for a dual tone, the nominal values of the frequency in Hz, level in dBm, time on and time off in ms for Frequency 1 and Frequency 2, where Frequency 1 is the lower of the two frequencies.
	Frequency	Level	Time On	Time Off
Frequency 1	`300 Hz`	`-18 dBm`	`250 ms`	`250 ms`
Frequency 2	`480 Hz`	`-18 dBm`	`250 ms`	`250 ms`

Notes:

For a dual tone, Frequency 1 must be the lower of the two frequencies. For tritones, Frequency 1 must be the first tone, Frequency 2, must be the second tone, and Frequency 3 must be the third tone in the sequence.
Use 9% as a guideline only in calculating minimum and maximum frequency values. With smaller absolute numbers, a larger percentage should be used. Also, you need to ensure that the range specified by minimum and maximum values for one frequency do not overlap with that specified by the values for another frequency.

All time values must be rounded to the nearest 20 ms.

Example call progress tone calculations

Frequency 1

Frequency 2

Minimum

= 300 - 9%

= 300 - 27

= 273 Hz

Maximum

= 300 + 9%

= 300 + 27

= 327 Hz

Minimum

= 480 - 9%

= 480 - 43

= 437 Hz

Maximum

= 480 + 9%

= 480 + 43

= 523 Hz

Level 1

Level 2

Minimum

= -18 + (-6)

=-24 dBm

Maximum

= 0 dBm

Minimum

= -18 + (-6)

= -24 dBm

Maximum

= 0 dBm

Time On 1

Time On 2

Minimum

= 250 - 15%

= 250 - 38

= 212

= 200 ms

Maximum

= 250 + 15%

= 250 + 38

= 288

= 300 ms

Minimum

= 250 - 15%

= 250 - 38

= 212

= 200 ms

Maximum

= 250 + 15%

= 250 + 38

= 288

= 300 ms

Time Off 1

Time Off 2

Minimum

= 250 - 15%

= 250 - 38

= 212

= 200 ms

Maximum

= 250 + 15%

= 250 + 38

= 288

= 300 ms

Minimum

= 250 - 15%

= 250 - 38

= 212

= 200 ms

Maximum

= 250 + 15%

= 250 + 38

= 288

= 300 ms

Recognizing double rings

Two ring tones should be defined when a double ring tone needs to be detected. A double ring tone is one in which the ring sequence is: ring...short pause...ring...long pause. The sequence, however, might not start at the beginning, which means that what Blueworx Voice Response detects is: ring...long pause...ring...short pause. To detect either sequence, then, you must define two tones, each with the same frequencies and levels, but with different cadences. One is defined as the first portion of the ring (ring...short pause), and the other is defined as the second portion (ring...long pause). This enables faster, more efficient detection of double ring tones.