參數(shù)資料
型號(hào)： U4084B
英文描述： Low-Voltage, Voice-Switched Circuit for Hands-Free Operation
中文描述： 低電壓，語(yǔ)音開(kāi)關(guān)電路免提操作
文件頁(yè)數(shù)： 20/26頁(yè)
文件大?。?/td> 544K
代理商： U4084B
U4084B
TELEFUNKEN Semiconductors
Rev. A1, 31-Jan-97
Preliminary Information
20 (26)
Some comments on the graph (figure 22):
Acousting coupling and side-tone coupling were not
included in equations 6 and 11. Those couplings will
affect the actual performance of the final speaker-
phone due to their interaction with speech at the
microphone, and the receive signal coming in at Tip/
Ring. The effects of those couplings are difficult to
predict due to their associated phase shifts and fre-
quency response. In some cases, the coupling signal
will add, and other times substract from the incoming
signal. The physical design of the speakerphone en-
closure, as well as the specific phone line to which it
is connected, will affect the acoustic and side-tone
couplings, respectively.
The M
R
line helps define the maximum acoustic
coupling permissible in a system, which can be found
from the following equation:
R
1
2
R
3
G
MA
Equation 12 is independent of the volume control setting.
Conversely, the acoustic coupling of a designed system
helps determine the minimum slope of that line. Using the
component values of figure 2 in equation 12 yields a
G
AC(MAX)
of –37 dB. Experience has shown, however,
that an acoustic coupling loss of >40 dB is desirable.
G
AC(MAX(
. . . . . 12
The M
T
line helps define the maximum sidetone cou-
pling (G
ST
) permissible in the system, which can be
found from the following equation:
R
1
2
R
2
Using the component values of figure 2 in equation 13
yields a maximum side-tone of 0 dB. Experience has
shown, however, that a minimum of 6.0-dB loss is prefer-
able.
G
ST
. . . . . 13
The above equations can be used to determine the resistor
values for the level detector inputs. Equation 5 can be
used to determine the R
1
, 3 ratio and equation 9 can be
used to determine the R
1
–R
2
ratio. In figure 21, R
1
–R
4
each represent the combined impedance of the resistor
and coupling capacitor at each level detector input. The
magnitude of each RC’s impedance should be kept within
the range of 2.0 to 15 k in the voiceband (due to the typi-
cal signal levels present) to obtain the best performance
from the level detectors. The specific R and C at each
location will determine the frequency response of that
level detector.
Application Information
Dial-Tone Detector
The threshold for the dial-tone detector is internally set at
15 mV (10 mV
rms
) below V
B
(see figure 5). That
threshold can be reduced by connecting a resistor from RI
to ground. The resistor value is calculated from:
V
V– 1
where V
B
is the voltage at Pin 12, and V the amount of
threshold reduction. By connecting a resistor from V
S
to
RI, the threshold can be increased. The resistor value is
calculated from:
V
S
–V
B
V
where V is the amount of the threshold increase.
Background-Noise Monitors
R
10 k
R
10 k
– 1
For testing or circuit analysis purposes, the transmit or
receive attenuators can be set to the “on” position by
disabling the background noise monitors, and applying a
signal so as activate the level detectors. Grounding the
CPR pin will disable the receive background-noise
monitor, thereby indicating the “presence of speech” to
the attenuator control block. Grounding CPT does the
same for the transmit part.
Additionally, the receive background-noise monitor is
automatically disabled by the dial-tone detector when-
ever the receive signal exceeds the detector’s threshold.
Transmit/Receive Detection Priority
Although the U4084B was designed to have an idle mode
such that the attenuators are halfway between their full-on
and full-off positions, the idle mode can be biased towards
the transmit or the receive side. By doing so, gaining
control of the circuit from idle will be easier for that side
towards which it is biased since that path will have less
attenuation at idle.
By connecting a resistor from C
T
(Pin 11) to ground, the
circuit will be biased towards the transmit side. The resis-
tor value is calculated from:
V
B
V– 1
where:
R
T
= 120 k (typ.) connected between Pin 11 and 12.
V = V
B
– V11 (see figure 8).
By connecting a resistor from C
T
(Pin 11) to V
S
, the cir-
cuit will be biased towards the receive side. The resistor
value is calculated from:
V
S
– V
B
V
The switching time will be somewhat affected in each
case due to the different voltage excursions required to get
to transmit and receive from idle. For practical consider-
ations, the V shift should not exceed 100 mV.
R
R
T
R
R
T
– 1
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
U4084B-FL 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Speakerphone Circuit
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U4087B 制造商:TEMIC 制造商全稱:TEMIC Semiconductors 功能描述:Low Voltage Voice Switch Interface Circuit for Hands-free Operation in Telephone
U4087B-FP 制造商:TEMIC 制造商全稱:TEMIC Semiconductors 功能描述:Low Voltage Voice Switch Interface Circuit for Hands-free Operation in Telephone
U4089B 制造商:ATMEL 制造商全稱:ATMEL Corporation 功能描述:MONOLITHIC INTEGRATED FEATUREPHONE CIRCUIT
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