Matrix Telecom SARVAM UMG System Manual page 167

This parameter allows you to increase near-end echo cancellation on the FXO Port. Near-end echo is
primarily caused due to the mismatch between AC Termination Impedance (presented by FXO Port of
SARVAM UMG to the line) and CO Termination (Impedance presented by the Central Office to the line) as
well as the transmit and receive signal path.
By correcting the line impedance mismatch, you can increase near-end echo cancellation. This is done by
selecting the AC Termination Impedance, CO Termination and a Line Type that closely models the line
connecting the FXO Port of SARVAM UMG to the Central Office.
• In CO Line Type, select a line type that closely models the line connecting SARVAM UMG to the Central
Office. You may select a specific EIA line model (EIA-0 to EIA-7) or a specific wire gauge with it's length
(2000 ft. 22/24/26awg). Default: None.
You are recommended to conduct the AC Impedance Test for the line connected to the FXO Port to
determine the most appropriate values for the AC Termination Impedance, CO Termination and the CO
Line Type. For more information see the topic
• Rx Gain enables you to adjust the volume level of the speech received from the remote party. Select the
Rx Gain accordingly. Default: +0dB.
• Tx Gain enables you to adjust the volume level of the speech transmitted to the remote party. Select the
Tx Gain accordingly. Default: +0dB.
• In On-Hook Speed, set the time period required for the line-side device (DAA) to go On-hook.
It is the time duration between On-hook bit clearance until loop current equals zero. You can select —
<0.5, 3 or 26. Default: <0.5 msec.
• In OFF- Hook Speed, set the time that would be required by the line transients to settle. Only after this
time period, the transmission or reception can take place. You can select — 512, 128, 64 or 8. Default: 8
msec.
• If you want to limit the loop current, select the Current Limiting check box. The Loop Current will be
limited to a maximum of 60mA. Default: Disabled.
• Set the Minimum Loop Current required by the line-side device (DAA) to operate. You can select — 10,
12, 14 or 16 — as per your requirement. Default: 10 mA.
• Set the TIP-RING Voltage (Volts) to adjust the TIP/Ring Voltage on the line side. You can select — 3.1,
3.2, 3.35 or 3.5. Default: 3.5 volts.
In countries where low voltage is required, use lower TIP/RING voltage. Adjust the values of the TIP-RING
Voltage to match your country requirements.
• Set the Ringer Impedance — High or Synthesized — for the FXO Port according to your country-specific
requirement.
High signifies 20 M Ringer Impedance. This is the default Ringer Impedance provided on the line side
by the DAA module of the FXO Port. The DAA Module can provide higher impedance when Synthesized
impedance is selected.
Some countries like Poland, South Africa and Slovenia require higher ring impedance which is achieved by
the DAA module, when Ringer Impedance is set to Synthesized impedance. Default: High.
161
"AC Impedance Test (FXO)".
Matrix SARVAM UMG System Manual