SAGEM 3P@C

„DS indicates Downstream

1.1.1.58Related 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 1-8The reference values for the main parameters of the voice splitter

Test item

Condition

Reference index

 

 

Short-circuit DC resistance

DC resistance (Ω)

Line A and B

= 25Ω

 

 

Open DC resistance = 5MΩ

Reflection

300-500 Hz

>14+2(f-3) dB

500-2000 Hz

18dB

attenuation (dB)

2000-3400 Hz

> 18-0.28(f-20) dB

 

Longitudinal

200-1000 Hz

58 dB

balance (dB)

1000-3000 Hz

53 dB

1.1.1.59Conditions 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:

3P@C Installation Manual

Page 12-2

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