ISD-T360 ETC [List of Unclassifed Manufacturers], ISD-T360 Datasheet - Page 54

• 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]

CONSTANT ENERGY
The constant-energy detector reports the pres-
ence of constant energy in the range 200Hz to
3400Hz. It is intended to detect both white and
pink noise and can be used to detect line dis-
connection during recording.
It is recommend to use the constant energy
mechanism in conjunction with the no-energy
(VOX) mechanism.
The following tunable parameters control the
operation of the constant-energy detector:
NO ENERGY (VOX)
The no-energy detector reports when the energy
in the frequency range 200Hz to 3400Hz remains
below a preprogrammed threshold for a prepro-
grammed time-out. A programmable tolerance
is allowed.
It is recommend to use the no-energy (VOX)
mechanism in conjunction with the constant-en-
ergy mechanism.
The following tunable parameters control the
operation of the no-energy (VOX) mechanism:
2-14
CONST_NRG_DET_TIME_COUNT
CONST_NRG_DET_TOLERANCE_TIME
CONST_NRG_DET_LOW_THRESHOLD
CONST_NRG_DET_HIGH_THRESHOLD
VOX_DET_ENERGY_THRESHOLD
VOX_DET_TIME_COUNT
VOX_DET_TOLERANCE_TIME
Figure 2-2: Busy-Tone Detector—Default Cadence Specification
[E
1
–
E
3
] < 100 ms [S
E
1
1
S
–
1
S
3
] < 100 ms 100 < E
E
2
2.3.4
The speakerphone feature lets the user commu-
nicate through a telephone line, using the unit’s
speaker and the microphone instead of its hand-
set. The speakerphone processes signals sent
from the line to the speaker, and from the micro-
phone to the line. It also performs the necessary
switching, attenuation and echo cancellation
on the signals present on the line/speaker.
The ISD-T360SB speakerphone is simple to use; it
requires no special hardware or training for the
echo cancelers. The gain control is fully digital,
which eliminates the need for analog gain con-
trol hardware.
The speakerphone features two types of echoes,
the electrical echo (line or circuit) and the
acoustic echo. The electrical echo is a result of
an imperfect impedance match between the 4-
to 2-wire interface (hybrid) and the line imped-
ance. The electrical echo, relatively short term,
has a transfer function that varies slowly. The
second echo, the acoustic echo, is a line imped-
ance returning from the speaker to the micro-
phone. This echo is relatively long term, and its
transfer function may vary quite quickly if
anyone, or anything, moves in the room. Both
echoes must be canceled to achieve a high-
quality hands-free system.
For more details of the speakerphone tunable
parameters refer to table 2-9 of the Command
Description section.
i
< 1680 ms 70 < S
S
FULL-DUPLEX SPEAKERPHONE
2
E
3
i
< 1220 ms
Voice Solutions in Silicon
S
3
2—SOFTWARE
™