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参数资料
| 型号： | ILA1068N |
| 厂商： | Electronic Theatre Controls, Inc. |
| 英文描述： | Versatile Telephone Transmission Circuit with Dialler Interface |
| 中文描述： | 多功能电话传输电路拨号器接口 |
| 文件页数： | 4/11页 |
| 文件大小： | 352K |
| 代理商： | ILA1068N |
ILA1068
4
Input MUTE
A HIGH level at MUTE enables the DTMF input and
inhibits the microphone and the receiving amplifier
inputs.
A LOW level or an open circuit has the reverse
effect. MUTE switching causes only negligible clicks
at the earpiece outputs and on the line.
Dial-tone multi-frequency input DTMF
When the DTMF input is enabled dialling tones may
be sent on to the line. The voltage gain from DTMF
to LN is typically 25.5 dB (when R7 = 68 K
) and
varies with R7 in the same way as the microphone
amplifier. The signalling tones can be heard in the
earpiece at a low level (confidence tone).
Receiving amplifier IR, QR-, QR+ and GAR
The receiving amplifier has one input (IR) and two
complementary outputs, a non-inverting output QR+
and an inverting output QR-. These outputs may be
used for single-ended or for differential drive
depending on the sensitivity and type of earpiece
used. Gain from IR to QR+ is typically 25 dB (when
R4 = 100 K
). This is sufficient for low-impedance
magnetic or dynamic microphones, which are suited
for single-ended drive. By using both outputs
(differential drive), the gain is increased by 6dB.
This feature can be used when the earpiece
impedance exceeds 450
, (high-impedance dynamic
or piezoelectric types).
The output voltage of the receiving amplifier is
specified for continuous-wave drive. The maximum
output voltage will be higher under speech
conditions where the ratio of peak to RMS value is
higher.
The receiving amplifier gain can be adjusted between
17 dB and 33 dB with single-ended drive and
between 26 dB and 39 dB with differential drive to
suit the sensitivity of the transducer used. The gain
is set by the external resistor R4 connected between
GAR and QR+. Overall receive gain between LN and
QR+ is calculated by subtracting the anti-side-tone
network attenuation (32 dB) from the amplifier gain.
Two external capacitors, C4 = 100 pF and C7 =
10 x C4 = 1 nF, are necessary to ensure stability. A
larger value of C4 may be chosen to obtain a first-
order, low-pass filter. The ‘cut-off’ frequency
corresponds with the time constant R4 x C4.
Automatic gain control input AGC
Automatic line loss compensation is achieved by
connecting a resistor (R6) between AGC and V
EE
.
The automatic gain control varies the gain of the
microphone amplifier and the receiving amplifier in
accordance with the DC line current.
The control range is 5.8 dB which corresponds to a
line length of 5 km for a 0.5 mm diameter twisted-pair
copper cable with a DC resistance of 176
/km and
average attenuation of 1.2 dB/km.
Resistor R6 should be chosen in accordance with the
exchange supply voltage and its feeding bridge
resistance (see Table 1). Different values of R6 give
the same ratio of line currents for start and end of the
control range. If automatic line loss compensation is
not required,
AGC may be left open. The amplifiers
then all give their maximum gain as specified
.
Table 1
Values of resistor R6 for optimum line-loss
compensation, for various usual values of exchange
supply voltage (V
exch
) and exchange feeding bridge
resistance (R
exch
); R9 = 20
.
V
exch
(V)
R
exch
(
)
R
exch
(
)
24
61.9
48.7
36
100
78.8
48
140
110
60
-
-
Power-Down input (PD)
During pulse dialling or register recall (timed loop
break), the telephone line is interrupted. During these
interruptions, the telephone line provides no power
for the transmission circuit or circuits supplied by
V
CC
. The charge held on C1 will bridge these gaps.
This bridging is made easier by a HIGH level on the
PD input, which reduces the typical supply current
from 1mA to 55 mA and switches off the voltage
regulator, thus preventing discharge through LN.
When PD is HIGH, the capacitor at REG is
disconnected with the effect that the voltage
stabilizer will have no switch-on delay after line
interruptions. This minimizes the contribution of the
IC to the current waveform during pulse dialling or
register recall. When this facility is not required, PD
may be left open-circuit.
Side-tone suppression
400
600
800
R
exch
(
)
1000
R
exch
(
)
R6(K
)
-
-
68
93.1
120
60.4
82
102
The anti-side-tone network, R1//Z
line
, R2, R3, R8, R9
and Z
bal
(see Fig.5) suppress the transmitted signal in
the earpiece. Maximum compensation is obtained
when the following conditions are fulfilled:
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