The Coefficient Configuration File - 3Com VCX V7111 User Manual

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 VCX V7111/FXS and VCX
V7111/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 VCX V7111 use the Embedded Web Server (see
Settings on page 129) or alternatively specify the FXS/FXO coeff.dat file name in the
gateway's ini file (see Loading the Auxiliary Files via the ini File
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.
156
on page 144).
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