isd-t360sb ETC-unknow, isd-t360sb Datasheet - Page 47

• Manufacturer Part Number: isd-t360sb
• Manufacturer: ETC-unknow

2—SOFTWARE
2.3.2
The VoiceDSP processor detects DTMF tones, thus enabling remote control operations. Detection is active
throughout the operation of the VoiceDSP processor. Detection can be configured using the SDET (Set
Detectors Mask) command, which controls the reporting of the occurrence of tones, and the RDET (Reset
Detectors) command which resets the detectors. The accuracy of the tone length, as reported by the
tone detectors, is ±10 ms.
DTMF detection may be reported at the starting point, ending point, or both. The report is made through
the status word (for further details, see GSW command).
For further details about tunable parameters refer to Table 2-6 of the Command description section. The
DTMF detector performance, as measured on the line input using an ISD-DS360-DAA board, is summa-
rized below in Table 2-1.
*
1.
2.
3.
4.
5.
DTMF SW AGC
In order to remove the linkage between the HW AGC and the detection level of the DTMF detector, two
new tunable parameters are added. These tunable parameters define the gain of the SW AGC for DTMF
signals.
DTMF_DET_AGC_IDLE - SW AGC for DTMF detection in Idle and Record states. When incrementing this tun-
able by 1, the dynamic range is increased by 3 dB.
DTMF_DET_AGC_PLAY - SW AGC for DTMF detection in Play and Tone_Generate states. When increment-
ing this tunable by 1, the dynamic range is increased by 3 dB.
For more information on the SW AGC commands, refer to index values 60 and 61 in Table 2-6 of the
Command Description section.
ISD
Detection Sensitivity
Accepted DTMF Length
Frequency Tolerance
S/N Ratio
Minimum Spacing
Normal Twist
Reverse Twist
Performance depends on the DAA design. For reliable DTMF detection:
•
•
Tune parameters 60 and 61 affect DTMF detection sensitivity. The detection sensitivity is -34 dBm when these
tunable parameters get their maximum value of 5.
Performance with echo canceler is 10 dB better than without echo canceler. For a silent message, detection
sensitivity is - 34 dBm, with echo canceler.
The accuracy of reported DTMF tones is ±10 ms.
If the interval between two consecutive identical DTMF tones is less than, or equal to, 20 ms, the two are detected
as one long DTMF tone. If the interval between two consecutive identical DTMF tones is between 20 ms and 45
ms, separate detection is unpredictable.
Determined by the DTMF_REV_TWIST tunable parameter value.
A hardware echo canceller, that attenuates the echo by at least 6 dBm, is required during playback.
The HW AGC, if present, must be disabled during playback.
DTMF DETECTION
5
4
1
3
Table 2-1: DTMF Detector Performance*
Performance depends on the message being played.
>50 ms
±1.5%
12 dB
>50 ms
8 dB
4 dB or 8 dB
Play/IVS Synthesis
2
-34 dBm
>40 ms
±1.5%
12 dB
>45 ms
8 dB
4 dB or 8 dB
Record/Idle
ISD-T360SB
2-11