Sagem 4450E - Manual (Page 159)

SAGEM 3P@C
3P@C Installation Manual
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SAGEM SA
„ DS indicates Downstream
1.1.1.58 Related Parameters of ADSL Voice Splitter
The copper wire bears the original voice signals and the new ADSL signals, because the voice signal takes the
form of low-frequency signal, but ADSL takes the form of high-frequency signal. We can see from Figure 12-1,
ADSL frequency range, the voice signal frequency band is 0 ~ 4KHz, but the ADSL signal frequency band is 24K
~ 1.1MHz.To prevent the high frequency signals from impacting on the voice signals and to ensure the quality of
communication, the front end of the PSTN switch and the line of the subscriber line end are added with the voice
splitter. The voice splitter is in fact a Low Pass Filter (LPF), which only permits the voice signals to pass and
blocks the high frequency ADSL signals. The ADSL voice splitter has the following pass-band characteristics as
shown in the figure below:
Figure 12-2 The pass-band characteristics of the ADSL voice splitter
The voice splitter uses the passive devices, connected on the line in series, so it has a high
reliability, but with the time elapse, it will also be of aged deterioration, mainly reflecting in the
following respects:
„ The increase of the DC loop resistance affects the connection rate of the ADSL line.
„ Aging of capacitance affects the communication quality and the ADSL service.
The reference values of the main parameters of the voice splitter is shown in the table below:
Table 1-8 The reference values for the main parameters of the voice splitter
Test item Condition Reference index
Short-circuit DC resistance
= 25Ω
DC resistance (Ω) Line A and B
Open DC resistance = 5MΩ
300-500 Hz >14+2(f-3) dB
500-2000 Hz 18dB
Reflection
attenuation (dB)
2000-3400 Hz > 18-0.28(f-20) dB
200-1000 Hz 58 dB Longitudinal
balance (dB)
1000-3000 Hz 53 dB
1.1.1.59 Conditions for ADSL central office end setting
The Central office terminal of ADSL is the equipment featured by easy management and operation, it can meet
the demands for different service types through the setting of some constraint-based parameters, and achieve
the better effect of line connection by the effective and reasonable configuration of the line parameters. The
setting of ADSL parameters is shown in the table below: