isd-t360sb ETC-unknow, isd-t360sb Datasheet - Page 50

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

ISD-T360SB
CONSTANT ENERGY
The constant-energy detector reports the pres-
ence of constant energy in the range of 200Hz to
3400Hz. It is intended to detect both white and
pink noise and can be used to detect line discon-
nection during recording.
It is recommended to use the constant energy
mechanism in conjunction with the no-energy
(VOX) mechanism.
The following tunable parameters control the op-
eration of the constant-energy detector:
NO ENERGY (VOX)
The no-energy detector reports when the energy
in the frequency range of 200Hz to 3400Hz re-
mains below a pre-programmed threshold for a
pre-programmed time-out. A programmable tol-
erance is allowed.
It is recommended to use the no-energy (VOX)
mechanism in conjunction with the constant-en-
ergy mechanism.
The following tunable parameters control the op-
eration of the no-energy (VOX) mechanism:
2.3.4
The speakerphone feature lets the user communi-
cate through a telephone line, using the unit’s
speaker and microphone instead of its handset.
The speakerphone processes signals sent from the
line to the speaker, and from the microphone to
the line. It also performs the necessary switching,
attenuation and echo cancellation on the signals
present on the line/speaker.
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
FULL-DUPLEX SPEAKERPHONE
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 control
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 impedance.
The electrical echo, relatively short term, has a
transfer function that varies slowly. The second
echo, the acoustic echo, is a line impedance re-
turning from the speaker to the microphone. This
echo is relatively long term, and its transfer func-
tion may vary quite quickly if anyone, or anything,
moves in the room. Both echoes must be can-
celed to achieve a high-quality hands-free
system.
For more details of the speakerphone tunable pa-
rameters refer to Table 2-9 of the Command De-
scription section.
SPEAKERPHONE TERMINOLOGY
Send Path
The signal path from the microphone (near-end
speaker) to the line (far-end listener). The micro-
phone is the input port, and line-out is the output
port of this signal path.
Receive Path
The signal path from the line (far-end speaker) to
the loudspeaker (near-end listener). The line-in is
the input port, and the speaker is the output port
for this signal path.
AEC
Acoustic Echo Controller. The part in the speaker-
phone algorithm that controls the echo in the
send path.
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