SIP User's Manual 448 Document #: LTRT-12801
MP-500 MSBG
8.4 FXS Coefficient File
The FXS Coefficient file (Coeff_FXS.dat) is used to provide best termination and
transmission quality adaptation for different line types for FXS interfaces. This adaptation is
performed by modifying the telephony interface characteristics (such as DC and AC
impedance, feeding current, and ringing voltage). The coeff.dat auxiliary file is produced
specifically for each market after comprehensive performance analysis and testing, and can
be modified on request. The current file supports US line type of 600 ohm AC impedance
and 40 V RMS ringing voltage for REN = 2. To load the coeff.dat file to the device, use the
Web interface or specify the FXS coeff.dat file name in the device's ini file (refer to
''Loading Auxiliary Files'' on page 238).
The Coeff.dat file consists of a set of parameters for the signal processor of the loop
interface devices. This parameter set provides control of the following AC and DC interface
parameters:
îš„ DC (battery) feed characteristics
îš„ AC impedance matching
îš„ Transmit gain
îš„ Receive gain
îš„ Hybrid balance
îš„ Frequency response in transmit and receive direction
îš„ Hook thresholds
îš„ Ringing generation and detection parameters
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.
In future software releases, it is to be expanded to consist of different sets of line
parameters, which can be selected in the ini file, for each port.
Note:
To configure the FXO coefficients, use the parameter CountryCoefficients
(described in Analog Telephony Parameters).
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