AudioCodes Media Pack MP-11x, User Manual

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User's Manual 314 Document #: LTRT-65432
MP-11x & MP-124
26.13 FXS/FXO Coefficient Types
The FXS Coefficient and FXO Coefficient types used by the device can be one of the
following:

US line type of 600 ohm AC impedance and 40 V RMS ringing voltage for REN = 2

European standard (TBR21)
These Coefficient types are used to increase return loss and trans-hybrid loss performance
for two telephony line type interfaces (US or European). This adaptation is performed by
modifying the telephony interface characteristics. This means, for example, that changing
impedance matching or hybrid balance doesn't require hardware modifications, so that a
single device is able to meet requirements for different markets. The digital design of the
filters and gain stages also ensures high reliability, no drifts (over temperature or time) and
simple variations between different line types.
The FXS Coefficient types provide best termination and transmission quality adaptation for
two FXS line type interfaces. This parameter affects the following AC and DC interface
parameters:

DC (battery) feed characteristics

AC impedance matching

Transmit gain

Receive gain

Hybrid balance

Frequency response in transmit and receive direction

Hook thresholds

Ringing generation and detection parameters

To select the FXO and FXS Coefficient types:
1. Open the Analog Settings page ( Configuration tab > VoIP menu > Media > Analog
Settings ). This page includes the Coefficient type parameters, as shown below:
Figure 26-11: FXS/FXO Coefficient Parameters in Analog Settings Page
2. From the 'FXS Coefficient Type' drop-down list (FXSCountryCoefficients), select the
required FXS Coefficient type.
3. From the 'FXO Coefficient Type' drop-down list (CountryCoefficients), select the
required FXO Coefficient type.
4. Click Submit .
5. Save your settings to the flash memory ("burn") with a device reset.