ISD-T360 ETC [List of Unclassifed Manufacturers], ISD-T360 Datasheet - Page 53

• Manufacturer Part Number: ISD-T360
• Description: VoiceDSP Digital Speech Processor with Master/Slave, Full-Duplex Speakerphone, Multiple Flash and ARAM/DRAM Support
• Manufacturer: ETC [List of Unclassifed Manufacturers]

2—SOFTWARE
BUSY AND DIAL TONES
Busy and dial-tone detectors work with a band-
pass filter that limits the frequency range in
which tones can be detected to 0–1100Hz.
Figure 1-1 shows the frequency response of this
band-pass filter.
The design of the busy-tone detector allows very
high flexibility in detecting busy tones with vary-
ing cadences.
The tunable parameters are divided into five
sets:
ISD
1.
2.
Busy Tone On-time and Off-time Range
Specification:
BUSY_DET_MIN_ON_TIME
BUSY_DET_MIN_OFF_TIME
BUSY_DET_MAX_ON_TIME
BUSY_DET_MAX_OFF_TIME
Busy Tone Cadence Control Specification
BUSY_DET_VERIFY_COUNT
BUSY_DET_TONE_TYPE
BUSY_DET_DIFF_THRESHOLD
BUSY_DET_VERIFY_COUNT determines the
number of On/Off cadences that detec-
tor should detect before reporting busy
tone presence.
BUSY_DET_DIFF_THRESHOLD describes the
maximum allowed difference between
two compared On or Off periods, as de-
0
–10
–20
–30
–40
0
Figure 2-1: Busy and Dial-Tone Band-Pass Filter Frequency Response
200
400
600
800
Frequency (Hz)
1000
3.
4.
termined by the BUSY_DET_TONE_TYPE
tunable parameter.
BUSY_DET_TONE_TYPE specifies the type of
cadences that are supported.
Legal values are:
Two cadences only
Three cadences only
Both two and three cadences.
The acceptance criteria for two cad-
ences:
[E1–E3] < BUSY_DET_DIFF_THRESHOLD
and
[S1–S3] < BUSY_DET_DIFF_THRESHOLD
The
cadences:
[E1–E4] < BUSY_DET_DIFF_THRESHOLD
and
[S1–S4] < BUSY_DET_DIFF_THRESHOLD
Busy and Dial Tone Energy Thresholds
TONE_DET_ON_ENERGY THRESHOLD
TONE_DET_OFF_ENERGY THRESHOLD
Busy Detection Time
BUSY_DET_MIN_TIME
1200
acceptance
1400
1600
criteria
1800
for
2000
three
2-13