BL1062A1
Input MUTE
When MUTE is LOW or open-circuit, the DTMF input is enabled and the microphone and
receiving amplifier inputs are inhibited. The reverse is true when MUTE is HIGH. MUTE switching
causes only negligible clicking on the line and earpiece output. If the number of parallel sets in use
causes a drop in line current to below 6 mA the DTMF amplifier becomes active independent to the
DC level applied to the MUTE input.
Dual-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 kΩ) and varies with R7 in the same way as
the microphone gain. The signalling tones can be heard in the earpiece at a low level (confidence
tone).
Receiving amplifier IR, QR and GAR
The receiving amplifier has one input (IR) and a non-inverting output (QR). The IR to QR gain is
typically 31 dB (when R4 = 100 kΩ). It can be adjusted between 20 and 31 dB to match the
sensitivity of the transducer in use. The gain is set with the value of R4, which is connected
between GAR and QR. The overall receive gain, between LN and QR, is calculated by subtracting
the anti-sidetone network attenuation (32 dB) from the amplifier gain. 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 peak to RMS ratio is higher.
Automatic Gain Control input AGC
Automatic line loss compensation is achieved by connecting a resistor (R6) between AGC
and VEE . 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
Ω/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. The ratio of start and stop currents
of the AGC curve is independent of the value of R6. If no automatic line-loss compensation is
required the AGC pin may be left open-circuit. The amplifiers, in this condition, will give their
maximum specified gain.
Enhanced EMC performance
The input pins BL1062A1 is added RC filters to improve the EMC performance, so the
telephone sets which used BL1062A1 are easily to handle the EMC design.
LIMITING VALUES
SYMBOL
PARAMETER
CONDITIONS
MIN. MAX. UNIT
V
V
LN
positive continuous line voltage
12
13.2
V
V
−
−
LN(R)
repetitive line voltage during
switch-on or line interruption
repetitive peak line voltage for
a 1 ms pulse per 5 s
V
LN(RM)
28
V
R9 = 20 Ω; R10 = 13 Ω;
see Fig.6
−
I
P
T
T
line
line current
total power dissipation
operating ambient temperature
storage temperature
140
600
+75
+125
mA
mW
oC
R9 = 20 Ω
R9 = 20 Ω
−
−
−25
−40
tot
amb
stg
oC
http://www.belling.com.cn
- 3 -
8/25/2006
Total 7 Pages
Wrote by 2006
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