User`s manual

MediaPack SIP User’s Manual 16. Configuration Files
Version 4.6 247 June 2005
16.3 The Coefficient Configuration File
The Coeff_FXS.dat and Coeff_FXO.dat files are used to provide best termination and
transmission quality adaptation for different line types for FXS and FXO gateways respectively.
This adaptation is performed by modifying the telephony interface characteristics (such as DC
and AC impedance, feeding current and ringing voltage).
The coeff.dat configuration 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 (for FXS) 40 V RMS ringing voltage for REN = 2.
To load the coeff.dat file to the MediaPack use the Embedded Web Server (refer to Section
5.6.4
on page 145) or alternatively specify the FXS/FXO coeff.dat file name in the gateway’s ini file
(refer to Section
5.8.2.1 on page 160).
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:
• 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
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.